My volt display started showing 11.7 in really hot weather, with A/C running while idling at traffic lights. Increased RPM's bring it up to mid/high 12's in the city, and while driving on the highway (headlights, radio and AC on) it got up to 13.9 - 14.1. Thinking that I was running on luck to get home (3 hour drive), I'm going to pull the alt and have it tested but not sure that a test can factor in the hot under-the-hood temps while under load.

My question...assuming it has a factory 108 amp alternator, is there reason not to replace it with the 200 amp alternator?

Although it is an old alternator - it was on the car when I purchased the car 4 years ago and was not visibly new(er) at that time. Battery replaced 2 years ago no other electrical problems noted. It might be just the internal regulator, but is it really worth putting new parts on old in this case?

It is up to you. What is your time worth, and how important to you?
My life is too short to screw around with an alternator. If I think it is bad, and the parts store tests it as bad, time for a new one. My days of putting brushes, regulators, and bearings in alternators are over, but I did repair them for years when I was younger.

Hi Dan,
Just an FYI, the '85 came with a 120 amp alternator. My '85 has had three of them replaced since I got it in '99

Hi Pete & Chuck,
I think I got my numbers crossed on the amperages - thanks for clarifying, Chuck. Any reason why you haven't tried a 200 amp alternator during one of your replacements?

I just pulled it off the car and although the sticker is long past being readable, I found the following stamped info: "Delco Remy" and 2 rows of numbers, the top: "1101 037 70A" and the bottom row reads: "??? 12V NEG". Anyway, this has me wondering...could it only be 70 amps - is that possible? Who knows what was PO's put on it??

Before pulling it out of the car I started it up, and had a DVM on the battery. The DVM and the display in the dash read exactly the same at all times.

Cold - it was reading 14.1-14.3. I pulled on the headlights, and turned on the AC and within 3-4 minutes readings were in the low 13's eventually dropping down as low as 12.6 when the fan kicked on. I could hear the alternator make a bit of a rattling noise when under max load and after running the car no more than 5 minutes the alternator was so hot, I couldn't hold the palm of my hand on it.

I'm thinking I was pretty lucky to in my 3 hour drive home last night.

Dan

if the voltage is dropping that low, the diodes are dying.

I would find a good local shop to rebuild it. The remans are JUNK.

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good one... there oughta be a country song somewhere in those lyrics!!! ha ha

More seriously...are you suggesting that because it is a Delco Remy that is worth considering having it rebuilt? My concern in this case is I don't know how many times the alternator could have already been changed on this car, and whether the one I have now is the exact one for it.

Dan, my '85 does exactly the same thing with the load on it the way you describe. 14.1 cold then turn on a/c & lights and it's down around 12.7. Turn everything off and it goes up to 13.8-13.9 Either we're both perfectly okay or both have weak alternators. As to your question about the bigger amp alt. if this one goes I will definitely change to the higher amperage. The reason I didn't earlier on is because the first change was right fter I got the car and the second change was enroute from Illinois to Atlanta and they would only replace it with the same as was on the car due to core charge. Personally, as long as mine is still showing that it is charging, even at 12.7 I will not replace it, however, I watch the gauge closely for anything out of order.

Chuck,
Interesting that the readings are so comparable - it was that little red idiot light that came on when I was 3 hours from home at dusk that got me a little unsettled. ha ha The car was idling a little lower than usual (in drive at a traffic light) but when I saw 11.7 volts flashing at me, I wasn't too comfortable.

Quick side question - I've been searching the forum and have seen lots of talk about this 200 amp alternator replacement mentioned above; which brand(s) is this and where is generally a good-priced place to get it? Any gotchas? With the audio gear I'm going to be dropping into my 92 toy, I expect I'm going to need something larger than stock, even with a big cap.

Thanks,

Tom / zxcasd

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The standard on a 92 is 124 amp. I bumped min up to a 140 when I replaced mine, but I'm not running extra gear. At least the 140 is fairly easy to get (NAPA).

Alterntors on 92s are maintainence items, ask Andy.

Understood - that's why I'm interested in just replacing it once and for all with this 200 that everyone seems to be talking about, since I'm turning a wrench on her anyway.

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Tom, no idea on "once and for all" but, I wouldn't think a 200 would outlast a stock one in a stock application. It'd probably do better in your app withe the amps,etc.

I just googled 200 amp alternator/92 corvette and got a bunch of hits.
http://www.alternatorparts.com/Extrem ... ifier%20CS-144%20type.htm

So, you may want to try that search.

Thanks, I got the million hits as well but was hoping someone here had already done the legwork and had a pointer. I also found a few on Ebay.

A question - is the ZR1 alternator the same as the Base? I see two on Ebay for 189 and 165 for the Base, but one at 130 that specifies the ZR1.

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I can see where the little red light would increase your pulse rate, mine never drops that low so you do have something going bad.

I ordered a 120 amp reman this morning from my perferred auto parts supplier here in town (NAPA). My car's RPO codes show it having a "120 amp generator". 2 prices (in CDN $) for what I am pretty sure is the same alternator... $149 for a unit with a limited warranty (I forget - either 30 days or 1 year) but it doesn't matter 'cause I didn't hesitate to go with the higher price of $198 because it comes with a lifetime warranty and roadside assistance. Given our C4s' reputation of going through alternators on a regular basis - I couldn't pass on the lifetime warr. and RA. Will pick it up tomorrow and install in the evening.

To upgrade the 85, I believe you'll have to file the top alternator bracket down. Be careful with this as you don't have much material to work with.

I think mine is still running on the original alternator.

Thanks for the tip, Coaster - I decided to go with the stock 120. Going to pop it in now and compare voltage readings to before.

All is good. New alternator installed - fired up at 14.3 on DVM and 14.5 on digital display. Settled down to 14.3 on the display after a couple of minutes and held steady at 14.3. Pulled on the headlights - no drop, switched on AC at max and it dropped and hovered around 13.8. When the fan kicked on it would drop momentarily to 12.9/13.1 and then stabilize back at 13.8. A couple of observations...the brand new alternator has the same kind of electrical hum/rattle when under heavy load as the old one had. After running for about 5-7 minutes under heavy load (coolant temp was only 89 C) the alternator was just as hot to the touch as the old one was.

All set for Beach Cruize this coming week-end. The largest Corvette car show/event in Ontario. See http://wasagabeachcorvetteclub.com/