Hi,
The other day while driving home, I noticed that my temperature gauge was WAY into the red. There were no trouble lights, smoke, chimes, or anything else to alert me of this condition. Hopefully, my '91 Z28 hasn't been in the state long, I have a couple of questions:

1. I HAD to use the car to go to an interview, and I was already running late SO- I drove it for about 30 minutes during which time the temp needle went first into the red, then proceeded back into the black (off the scale). Everything seems to have held together though, and I opened the hood once I parked- still okay, the overflow tank was boiling though and steam was spraying through the overflow tank cap. On the return trip, I made several cool-down stops. The car seems to run fine still, but I wonder if there are any components I need to check for heat damage?

2. Today, I checked out all the fuses, and did some wiring tests. I couldn't find any problems, but I did notice the fan (electric) did not go on. Bypassing the control circuit, I connected the + side of the fan to the battery and it ran fine. I now strongly suspect the fan to be the source of the problem, though I was surprised that it was making such a big difference even when I was driving 50-60mph, as I would expect the natural airflow to provide sufficient cooling at that speed. For now, I wired in a bypass connector so I can run the fan manually- at least I have transportation, but obvsiously this is a temporary solution.

3. I didn't have the manual for the car with me, so I figure that the problem lies either with the temp sensor not registering properly, or the fan relay malfunctioning. What tests can I do to determine where the problem lies, and where can I access the bad component(s)?

Thanks for any help or suggestions!
-Kevin

 

if you are going at speeds of about 50-60 MPH.. then there should of been plenty of air flowing through the radiator. unless you don't have ur air dam in place under ur car.. so check to make sure you have that.. and as far as you fan goes. it might be ur relay or wiring.

 

here is the schematic for the relay wiring harness.

use jumper to connect A to E (while ignition on) to see if the fan comes on. it it does.. then your relay might be the problem..

to test the relay. plug the harness back into the relay, and splice or probe a wire into F. and with ignition on, ground that wire.. the fan should come on. if it doesn't then replace your relay. if it DOES come on, then the problem may be in your wiring or temp switch..

 

Where is the fan relay on an RS? I checked out your schematic and I saw 3 of these relays, 1 on the passenger side and 2 on the drivers side

also, is the fan switch reachable from the top of the engine, or is it in the block itself

thanks!

 

well my two fan relays were located on the drivers side firewall, to the right of the master cyclinder.


when i changed my fan switch i had to jack the front of the car up and get to it from under the car.... its on the block way up top between the 6 & 8 cyclinders..

 

To ceck if your relay is good take a ohm meter and check ohm's across the coil which is D and F, 50 or greater Good, less than 50 I would replace. Hope this helps John

 

Fan relay on my 90 RS is on firewall, driver side, above brake system. It's the one farthest from side of car.

Stumps me that you have cooling problem at speed.

I have this problem with my 90 RS:

Cooling fan works when I straight-wire it (connecting A to E in above diagram). Fan also used to work when A/C was on (now doesn't do that either). Replaced the relay and all sensors and still same problem. If I leave it straight-wired, I blow fuses (too much amp draw for that hot-in-run wire (E). Checked continuity and seems to be fine along all wiring paths - conclusion - computer!

However, I installed a 180 thermostat and I never seem to run above 180 unless I'm stuck in traffic (or drive thru).

So I'm trying the cheap route for now (computer $130 or so) -
I ordered from Summit p/n PRM-19001 Perma-Cool Fan Wiring Kit (170 degree temp sensor & wires) $17.95 and p/n PRM-19002 (A/C Relay) $7.50. This should allow me to straight wire fan to battery with an inline 30 amp fuse. I'll keep all original sensors and relays in place so as to not confuse the computer. I should recieve this 9/5 or 9/6 and install ... Maybe a cheap solution for you as well - I'll let ya know if it worked out for me.