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| apdale | Odometer and Speedometer not working | ||
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Guru Newb
 
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I've got a 1984 Corvette with an automatic transmission that I became the owner of a month or so ago, car drives and runs well but there are several electrical problems I'm trying to run down. This is my first corvette, I've done some car repair before but I'm no expert.
The first problem I'd like to fix is the odometer nor the speedometer work, I believe that the odometer has been either rolled back or replaced (mileage reports ~@26k and the title reports 153k) but its not moving now so I have no idea how many miles are on the car. The speedo LCD does light up and reports 0 mph all the time. When the car is started a few different mphs are shown in what I believe to be the boot up tests as it is supposed to. I've removed the VSS (speed sensor) and checked that the driven gear is intact and that the VSS outputs a voltage when it is turned so I believe both of those are OK. That leaves the wiring as the next suspect in my book - I would have hoped that it would report the mileage incorrectly or inconsistently if it was a wiring issue but its possible that a connection was lost entirely. I'm not sure where or how to start tracing the wiring, I followed it from the VSS but can't find it where it comes up behind the engine. Any other ideas? Does this sound like it is a wiring issue? The previous owner stated that this was a fuse problem (which I doubted), I've replaced a couple of blown fuses and that hasn't helped any. Another possibly part failure is the drive gear, I have not tried measuring the output of the VSS with the drive wheels turning, not sure what the likelihood of that happening is but it would be good information. Any advice/help would be greatly appreciated. I was able to track down the 1984 FSM as a reference to look things up in but its not helped solve the problem so far. And for those that like pictures:  |
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Posted on: 2011/8/19 16:48
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| JeffK | Re: Odometer and Speedometer not working | ||
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Elite Guru
 
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Wow, that is a clean 84. I happen to like those wheels on our C4's.
I'm sorry I can't help you with your issue. The digital dashes in these cars are notorious for the gremlins. Welcome to the madhouse! Jeff |
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Posted on: 2011/8/19 17:22
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| captmike13 | Re: Odometer and Speedometer not working | ||
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Welcome aboard. I believe the odometer is still mechanical and uses a cable back to the transmission. I could be mistaken on that though.
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Posted on: 2011/8/19 20:46
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Mike| apdale | Re: Odometer and Speedometer not working | ||
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Quote:
Thanks! It is clean indeed, its been repainted at some point in its life. I agree with you about the wheels, they sure do look good!  |
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Posted on: 2011/8/19 20:49
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| apdale | Re: Odometer and Speedometer not working | ||
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Guru Newb
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Quote:
The odometer is definitely mechanical but I thought it was tied into the speedometer somehow, I believe when I get the speedo fixed the odometer issue will also be resolved (I hope). You could be right though...hopefully someone else can confirm how that works. |
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Posted on: 2011/8/19 20:54
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| Ultraman | Re: Odometer and Speedometer not working | ||
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2015 Memorial Day Car Show Winner!
 
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Welcome aboard! Someone will know about that and chip in soon I am sure. I am thinking that there comes a time when the whole dash cluster needs to be refurbished but that may not be the case here.
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Posted on: 2011/8/19 21:10
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| captmike13 | Re: Odometer and Speedometer not working | ||
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Elite Guru
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Also the dash cluster for the 84 are 84 only. You can't use a later yr to replace.
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Posted on: 2011/8/19 21:22
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| bogus | Re: Odometer and Speedometer not working | ||
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Grand Imperial Pooh-Bah
 
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I know the 87 IP had electronics, and the odo was powered by a cute little motor.
I think I need to review the Helm Manual. Welcome aboard!  |
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Posted on: 2011/8/20 2:40
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| KandBCorvette | Re: Odometer and Speedometer not working | ||
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Gold Sponsor Vendor
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Andy,
You are correct. The odo is powered by an electric motor. Since both components are not working & the OP is sure that the VSS is operational, then it is likely there is a bad IC on the driver board. |
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Posted on: 2011/8/29 21:38
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| apdale | Re: Odometer and Speedometer not working | ||
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Guru Newb
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How would I go about verifying that the signal from the VSS is getting to the IC on the driver board? Seems like that is another possible point of failure in addition to the driver board. How expensive is the driver board and how hard to replace? Does anyone know what else is controlled by that board?
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Posted on: 2011/9/1 12:48
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| KandBCorvette | Re: Odometer and Speedometer not working | ||
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Gold Sponsor Vendor
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The driver board is not a service part anymore, but it can be repaired-but it is not a DIY project. There are 14 critical IC's on the board that contol different functions of the display board.It is the top board in the cluster and controls all display functions and cruise control, if you have CC.
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Posted on: 2011/9/1 15:22
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| bogus | Re: Odometer and Speedometer not working | ||
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Grand Imperial Pooh-Bah
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I would verify the harness! Those early C4 harnesses are junk.
They can easily chaffe, split, crack and cause shorts. |
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Posted on: 2011/9/1 15:26
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| 76Nordic | Re: Odometer and Speedometer not working | ||
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Dumbass
 
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X2 what Andy said. I had some problems with my cluster on my 84. Read somewhere that the 2 big plugs can cause a bunch of different problems. Pulled it all apart and cleaned, and blew everything out, and I was good to go
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Posted on: 2011/9/1 15:40
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| apdale | Re: Odometer and Speedometer not working | ||
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Guru Newb
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Any tips on verifying the harness? I traced the wire as far as I could from the VSS and it looked alright. Where does it eventually end up so I can check for continuity. I'm an Electrical Engineer so I understand what things are supposed to be doing here, I'm just new to applying that knowledge to fixing car problems.
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Posted on: 2011/9/1 15:48
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| bogus | Re: Odometer and Speedometer not working | ||
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Grand Imperial Pooh-Bah
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This means you need to check the schematics in the Helm manual... or PDF, whichever version you have.
The schematics will get you what you need. |
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Posted on: 2011/9/1 16:12
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The single biggest problem with communication is the illusion that it has taken place. - George Bernard Shaw Education is the best tool to overcome irrational fear. - me |
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| apdale | Re: Odometer and Speedometer not working | ||
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Sounds good, I'll take a look and report back when I have new information. Thanks for all the input guys!
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Posted on: 2011/9/1 16:17
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| apdale | Re: Odometer and Speedometer not working | ||
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So I finally had some time to look into this today. I read through the manual and went through the steps for the code 24 that I'm getting. Its narrowed it down, but I'm not quite sure where to look next. See the picture below, I went through step one and got 13.4V, obviously thats not the 4-6V I should be seeing. The manual indicates that this is a problem with the I.P. Cluster. I unfortunately don't know what the I.P. is, could someone please enlighten me?
Thanks, Andrew https://picasaweb.google.com/lh/photo/ ... 31HmEGBkc?feat=directlink |
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Posted on: 2011/9/27 21:45
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| bogus | Re: Odometer and Speedometer not working | ||
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Grand Imperial Pooh-Bah
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IP = Instrument Panel.
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Posted on: 2011/9/28 6:29
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The single biggest problem with communication is the illusion that it has taken place. - George Bernard Shaw Education is the best tool to overcome irrational fear. - me |
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| apdale | Re: Odometer and Speedometer not working | ||
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Guru Newb
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Thanks! Guess I've got to start tracing some wires now.
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Posted on: 2011/9/28 11:59
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| CentralCoaster | Re: Odometer and Speedometer not working | ||
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Senior Guru
 
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How did you measure voltage on the VSS? I'm not sure you can do that.
Measure the ohms across it while turning the rear wheels on jack stands in neutral. Preferably with an analog guage, and you should see it oscillate. |
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Posted on: 2011/9/28 22:47
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| Matatk | Re: Odometer and Speedometer not working | ||
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Webmaster
 
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Sorry, I'm a little late to the game here. Welcome to the site. My steps are based on my 89 FSM which may vary slightly from yours.
From your first post, you say the speedo reads zero and the odometer doesn't work. Does the speedo always read zero while driving? Assuming the speedo isn't working (always zero), as I mentioned above - the code 24 testing is done with the wheels in the air, so you can idle and see if mph increases. If it doesn't display over 0 you disconnect the instrument panel and probe circuit 437 at the instrument panel connector to check for voltage. If it's over 10 v, the ip is bad or it's a bad connector to the ip. If not, it's shorted, bad ecm/ip connector, or bad ecm. The diagnostic aids help explain this, too. That being said, the FSM has a procedure for a non working speedo. It's not specified, but I take that to mean it doesn't display anything. For that, refer to section 8a. That's the electrical section. I then go to 8a-82-0 and 8a-82-7 which states if the speedo and odometer are not working, perform test a, terminals D11 and C15. This may vary for your year, so double check your manual. Test a is the cluster connector pinout test. You would have to remove the cluster and check for resistance at the connector. My 89 fsm says 350-500 ohms. If it's good, the IP is bad. If not, you need to do the vss troubleshooting test in 8a-33. Since you have to have the IP apart for all these tests anyway, might as well do them all to narrow it down. Matthew |
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Posted on: 2011/9/29 2:01
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| apdale | Re: Odometer and Speedometer not working | ||
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Guru Newb
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The speedo always reads zero, never seen it say anything else since I got the Corvette. It does its power on test and displays some speeds when initially started, so the display seems to work, so that leads me to believe the speedo itself is working.
I ran through the code 24 testing similar to what you said, I didn't disconnect the IP, I probed circuit 437 at the ECM connector (thats how the 84 FSM instructed). It was indeed over 10V. That being said, the FSM never says what would happen if the VSS or a wire coming out of the VSS is bad - wouldn't this be a possible cause of seeing over 10V at CKT 437? On the other hand, how expensive/hard to obtain is a replacment IP? Other things on the dash are working including the Tachometer, temp gauges, and the gas gauge - its only the displays related to speed that are not working. Looks like I need to go through the VSS troubleshooting in the electrical part of the FSM, I hadn't found that part yet. Thanks for the all the research into this! I'll definitely look into checking out what you've described. |
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Posted on: 2011/9/29 12:06
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| apdale | Re: Odometer and Speedometer not working | ||
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Guru Newb
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Quote:
I measured the voltage output of the VSS when I removed it to check that the driven gear wasn't broken. The VSS is basically a magnet and a coil so when I spun the VSS by hand and had a voltmeter across the terminals a voltage was generated. Not sure if that is the correct way of doing things, but it made since to me at the time. |
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Posted on: 2011/9/29 12:20
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| apdale | Re: Odometer and Speedometer not working | ||
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Matthew, I looked through the electrical section of my FSM and there isn't a VSS troubleshooting test anywhere in it, is there any way you could get me a digital copy of those pages? Also, where exactly is the IP, is it behind the LCDs? Thanks, Andrew |
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Posted on: 2011/9/29 16:40
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| bogus | Re: Odometer and Speedometer not working | ||
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Grand Imperial Pooh-Bah
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The IP IS the LCD - it's the entire "Instrument Panel".
That big ass thing with connectors, circuit boards, displays... that's the IP and you don't wanna know what it costs to replace. What I would do is contact Guru Vendor K&B Corvette Products. This thread has some info: http://www.corvette-guru.com/modules/ ... p?topic_id=15804&forum=72 Also, you can reach K&B at 770-777-1031. |
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Posted on: 2011/9/29 17:50
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The single biggest problem with communication is the illusion that it has taken place. - George Bernard Shaw Education is the best tool to overcome irrational fear. - me |
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| Matatk | Re: Odometer and Speedometer not working | ||
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Webmaster
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Quote:
As I mentioned, the 89 FSM will vary slightly from the 84. I will snap a photo later but it might be a day or two. As Andy indicated, the IP is the entire "dash" section that has all the displays, it comes out as one unit. Matthew |
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Posted on: 2011/9/29 23:36
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| apdale | Re: Odometer and Speedometer not working | ||
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No rush, not gonna have a chance this weekend anyways. Thanks for all the help guys!
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Posted on: 2011/9/29 23:59
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| 76Nordic | Re: Odometer and Speedometer not working | ||
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I will say this, with mine not sure the odometer was working or not, must be since it is showing almost 180K. But I was having probs with the tach and speedo. When I pulled the IP out, it has 2 big electrical plugs plugged into it. I blew out the plugs, cleaned the contacts on the IP where the plugs plugged in, changed the bulbs seeing I was already in there, just flat out cleaned everything. Put it all back together and voila, it all started to work again and hasn't stopped since. Just my .02
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Posted on: 2011/9/30 2:38
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| apdale | Re: Odometer and Speedometer not working | ||
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Hopefully its that easy! That'd be great. What bulbs are in there that I should change out? |
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Posted on: 2011/9/30 11:20
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| Matatk | Re: Odometer and Speedometer not working | ||
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He's referring to the light bulbs that backlight the panel. Go to http://www.batee.com/corvette/index.htm and look at the pictures. Matthew |
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Posted on: 2011/9/30 11:45
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2002 EBM convertible, Magnusson supercharger, cam, headers, etc. 1989 Corvette...RIP |
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| apdale | Re: Odometer and Speedometer not working | ||
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Guru Newb
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Quote:
That site looks like it'll be helpful on debugging the problem if its in the IP. Thanks for the link! |
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Posted on: 2011/9/30 12:03
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| Frank | Re: Odometer and Speedometer not working | ||
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Senior Guru
 
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Wow. Talk about good fortune. Like APdale I just got my first Corvette, I bought it in August and the Tach and the Speedo is not working and its the same color (Torch Red). The Code displays a "24" which I believe is the VSS. I was going to just jump in and replace the VSS but after reading the posts I'm having second thoughts. I did notice on its maiden voyage home that the IP faded out so I rapped it with my knuckle and it all came back on. Almost sounds like two problems here. Where should I start with my troubleshooting?
Thanks in advance! Love this car...... |
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Posted on: 2011/10/6 20:58
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| Matatk | Re: Odometer and Speedometer not working | ||
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Quote:
Usually if the IP fades in and out it's the grounds. I'd start by reading the batee site and getting an idea of what you're working with, then remove the IP and fix the grounds/possibly add an extra. Matthew |
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Posted on: 2011/10/6 22:20
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2002 EBM convertible, Magnusson supercharger, cam, headers, etc. 1989 Corvette...RIP |
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| BillH | Re: Odometer and Speedometer not working | ||
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The Stig Moderator
 
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Anybody read Gordon's book on Trouble Shooting the IP ?
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Posted on: 2011/10/6 22:23
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| Frank | Re: Odometer and Speedometer not working | ||
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Senior Guru
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Thanks Matthew, I'll start there. APDALE did you get yours fixed?
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Posted on: 2011/10/6 23:24
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| apdale | Re: Odometer and Speedometer not working | ||
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Guru Newb
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I've been busy at work and haven't had enough time to take everything apart. I'm hoping to get to it this coming week but not sure if thats going to happen or not. |
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Posted on: 2011/10/7 11:53
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| apdale | Re: Odometer and Speedometer not working | ||
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I sure haven't, I'm fairly new to the Corvette world, haven't even heard of it. Is it a recommended read for anyone having IP issues? |
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Posted on: 2011/10/7 11:55
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| BillH | Re: Odometer and Speedometer not working | ||
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The Stig Moderator
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Quote:
I've never read it, Andrew. But just saw in a mag that it is back in print. Gorden Killebrew was the Corvette engineer on the factory floor during the C4 production, sharp guy. It's called 84-89 Digital Dash Cluster Operation and Troubleshooting Guide. $30.00 |
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Posted on: 2011/10/7 12:33
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| Frank | Re: Odometer and Speedometer not working | ||
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Senior Guru
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Where exactly is this VSS located? Thanks.
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Posted on: 2011/10/8 22:01
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| apdale | Re: Odometer and Speedometer not working | ||
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Its right behind the transmission. There's a good chance the o-ring thats around it will break when you pry it out of there and you'll lose a little transmission fluid as well. I was able to find a replacement o-ring from Napa. Its held in by one screw and its got a connector on it that should have two wires coming out. If you need more help finding it, let me know.
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Posted on: 2011/10/9 2:02
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| Matatk | Re: Odometer and Speedometer not working | ||
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Frank - it's on the driver's side of the transmission/tailshaft housing. It's delicate so be careful if you plan on removing it. Looks like this:  |
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Posted on: 2011/10/9 13:32
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2002 EBM convertible, Magnusson supercharger, cam, headers, etc. 1989 Corvette...RIP |
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| Matatk | Re: Odometer and Speedometer not working | ||
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Webmaster
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Apdale - here are the FSM pages I promised you:
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Posted on: 2011/10/9 13:40
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2002 EBM convertible, Magnusson supercharger, cam, headers, etc. 1989 Corvette...RIP |
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| apdale | Re: Odometer and Speedometer not working | ||
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Guru Newb
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[quote]
Matatk wrote: Apdale - here are the FSM pages I promised you: Thanks! Those are a big help, they do a better job explaining how the VSS works than my FSM does and there are steps to figure out how to troubleshoot the VSS. Is it possible to find one of the Signal Generators referenced in the FSM? |
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Posted on: 2011/10/9 17:36
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| Matatk | Re: Odometer and Speedometer not working | ||
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They sell them used on ebay. http://cgi.ebay.com/ebaymotors/Kent-M ... Tools&hash=item53e96f612d If you were closer I have one, but I think you're out in Cali? |
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Posted on: 2011/10/9 19:04
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2002 EBM convertible, Magnusson supercharger, cam, headers, etc. 1989 Corvette...RIP |
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| KandBCorvette | Re: Odometer and Speedometer not working | ||
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Gold Sponsor Vendor
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One likely scenario is the ODO has been tampered with & has come loose from the mount and no longer engages the motor, an easy fix. The Battee info is way out of date.
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Posted on: 2011/10/9 19:38
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| Matatk | Re: Odometer and Speedometer not working | ||
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Might be out of date, but still address the majority of most owners issues...and I don't know of any better free resource out there. Do you? Matthew |
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Posted on: 2011/10/9 19:42
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2002 EBM convertible, Magnusson supercharger, cam, headers, etc. 1989 Corvette...RIP |
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| apdale | Re: Odometer and Speedometer not working | ||
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Guru Newb
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I'm in Kentucky, closer than Cali, but not real convenient. |
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Posted on: 2011/10/10 0:21
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| apdale | Re: Odometer and Speedometer not working | ||
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Guru Newb
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The odometer has definitely been tampered with...there are 154k on the title and 28k on the ODO. Would that also stop the speedometer from working? |
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Posted on: 2011/10/10 0:22
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| Matatk | Re: Odometer and Speedometer not working | ||
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Someone may have tried to replace it already since it wasn't working. |
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Posted on: 2011/10/10 2:17
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2002 EBM convertible, Magnusson supercharger, cam, headers, etc. 1989 Corvette...RIP |
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| Frank | Re: Odometer and Speedometer not working | ||
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Senior Guru
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Matatk. Thanks. I appreciate your efforts. Going to pull it this weekend.
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Posted on: 2011/10/11 22:41
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