Bought my son an 84 vette and as soon as you turn the ignition on the fan starts. Replaced the relay, no joy. Disconnected both the a/c pressure switch and the engine temp switch, fan still runs. Disconnecting the relay does stop the fan. Measure the green/white wire going into the relay and it goes straight to ground, but if I measure the wires from the a/c switch and the temp switch they read open. Is there a difference in the wiring for an 84 compared with later model years? I do have a check engine light on constant that I have to check. Can the ECM cause the fan to run constant? I've seen two different wiring charts for this, one looks like you have to have the grounds from either the a/c switch or temp switch to turn the relay on and power the fan. The other one takes inputs from both switches into the ECM and it sends the signal to the relay to energize the fan. Any help would be great!

Quote:
No
'84 is the only year to have no computer control of fan.
From mech switch in head or A/c switch over ride only


[IMG]http://i171.photobucket.com/albums/u309/vetteoz/electrical/Fan84.jpg[/IMG]



Quote:
I suggest someone has wired the relay control circuit direct to ground so fan runs all the time.
Commonly done by those that do not know any better

Should have continuity between grn/ white @ relay and terminal on switch; if not wire has been reworked

Temporary run a wire from relay to temp switch ( disconnect existing grn /wht ) and see what happens

Welcome to the site!

Vetteoz is spot on.

Here is a previous recent post with the same problem:

http://www.corvette-guru.com/modules/ ... e=&topic_id=14003&forum=1


As far as the check engine light, that is easily read by using a bent paperclip to jumper two pins in the ALDL port:

http://www.corvettebuyers.com/c4vettes/codes.htm


Matthew

Thanks for the input. I was taking measurements today and found that the contacts in the relay connector were shorting together. I won't buy another first year model edition of any car, too many problems. Have found numerus wiring problems on these connectors, mainly from the engine heat. Liquid tape is a lifesaver for bare wires on these connectors. Now onto the next problem, washer reservoir won't work. Found one on ebay, thought the old one was cracked,leaked out as soon as you filled it up, but pump won't work on either one. Can you remove the motor by loosening a nut inside the reservoir? What voltage are you suppose to get on the connector?

Quote:
The problematic type of relay you are dealing with was used through until at least '88 when GM changed to the Weather Pak type .
Common for wires on the early type plug to lose insulation and short out from vibration



[IMG]http://i171.photobucket.com/albums/u309/vetteoz/electrical/Relayfaults.jpg[/IMG]

Quote:

The windshield wiper switch is goofy on our cars. You have to press it in (down), not slide it for the washer to work. Did you try it that way?

Matthew

Thanks matatk,
Yes I pushed it down but still no joy. Is there a separate fuse for the pump? I don't think I'm getting 12 volts at the connector. Probably ties in somewhere with another connector that's shorting. Will try a battery charger on the pumps and see if they work with a known good 12 volt source.

Quote:


[IMG]http://i171.photobucket.com/albums/u309/vetteoz/electrical/Wiper.jpg[/IMG]

thanks for the diagram. Just out checking, have a good ground at the washer pump connector but am only getting 2.4 volts. Checked both pumps with a battery charger they work fine. Any ideas on what could be drawing the voltage down? Will check more later see what I can find.

I would check the easy stuff, look for broken wires, make sure there is power at the relay. I personally suspect the switch first. Door panel needs to come off for that. Check for corrosion, etc, at the contacts. Other than that it's tracing wires....ugh.

Matthew

Found the brown wire broke on one end coming from the temp switch, the other end was melted to the manifold thought I had found the problem, spliced new wire on but no joy. Finally just ran a new wire from the green/white wire at the relay to the temp switch and now works great. Kicks fan on at 238 till engine cools down to about 205. I don't know how the a/c ties into it but even with a/c running when the engine heats up fan will kick in. Thanks for all the help

Then it's working as it should