Coolant/Temp switch

[ltmark]

I need a little help on temp switches? I have an '85 L98.

1. There is the "temp" switch (1 wire) on the drivers side, midway on the block. 2. There is the "coolant switch" at the front of the block(2 wires)
3. There is the over-ride temp switch on the passenger side near #8 plug

#1, above, controls the readout temp on the dash (no other function, I believe?)

#2, front coolant temp, provides info to the ECM and, based on it's temp reading, ultimately turns on the primary fan, via the relay.

If I am correct, why does the over-ride switch (by #8 plug) go to ground at 195 degrees and turn on the secondary fan?

Since I never have like how hot it runs, and believing that the over-ride switch should not be a 195 degree'r, I have thought about doing the following:

Get a 210 +/- over-ride and wire it to the primary fan relay and change the primary white/green wire from the ECM to the "secondary" relay, thereby activating the aux fan. It seems to me that the engine would then run cooler and the ECM (higher setting) would serve as the fails-safe for over-temp.

Am I way out of the ballpark on this?

 

[Ken]

Your determination of the purpose of each of the switches, is on the money. As far as your solution for bringing the fan on sooner - that's (electricity) over my head. :L

 

[rrubel]

Is 85 different from the other years? On my 86, the sensor by #8 controls the readout to the dash and the (currently not installed) sensor between 1 and 3 would control the aux fan. The primary is controlled by the ECU.

If you want the car to run cooler, you shouldn't put a HIGHER-temp fan switch, but a LOWER one. Like 180.

Try a 180-degree thermostat first. If that doesn't help enough, you could install a manual switch inside the car to turn the aux fan on and off. This is what I did - one relay, some wires, and a SPST toggle screwed into the hush panel by the ALDL connector. Works like a champ, with the added benefit of being able to cool the radiator while the engine is off (like when waiting in line between runs at the drag strip).
[RICHR]

 

[ltmark]

Thanks for th info. I'm sure about the sensors. The problem is although the service manual and everything I've read says that 238 degrees is the "normal" main fan kick-in temp, I can't bring myself to accept that temp as healthy for an engine. I have a 160 degree stat in it and since I don't have the foggiest idea how you have the chip reprogramed, the only thing I see as reasonable is to send the ECM signal to the aux fan relay and the 195 over-ride signal to the main fan relay. I especially like this since the over-ride is by #8, which is historically the hottest area of the engine.

As it is now, when the ECM kicks the main fan in, it's getting it's signal from the Coolant temp switch located at the very front of the block. If it's 238 there, I'd hate to quess what the temp is at #8!!!!!

 

[ltmark]

One more thing.....I said I was thinking of going UP to a 200 or 210 sensor for the over-ride since it will be colder in the front of the engine and I don't want to screw up the effect the temp sensors have on all the other functions and on smooth operation. I don't want to have it so low that the fan ends up running all the time! I can live with 210, but 238 just doesn't seem healthy. At that temp, all the plastic sensor housings get brittle in no time and I can smell the heat at stop lights, etc. I'm no auto engineer, but I've been working on cars since I was 14 (now 57) and I do know one thing, heat and friction kill engines.......maybe Corvette designers know a heck of a lot more than me, but they're not going to buy me a new one when this one melts!

 

[WhalePirot]

'84 and early '85 Vettes used a simple thermo switch (pax side) to trigger the fan relay. The Vette catalogs are the easiest source for a lower trigger temp switch. Many complaints and many words on this forum about these hot-running-for-emissions engines.

The latter '85s, plus, moved this function to the ECM, which can be reprogrammed thru various means. Try searching the forum for it and shop e-bay for the equipment. Resetting the ECM fan trip temp is a rather simple job, with a programmer.

 

[ltmark]

Thanks very much. I'd love to be able to do it myself! Like I said, I'm no engine designer, but 238 is too damn hot!