94 z-28 cooling system

[magnum1968]

I have a cooling system problem... Symptoms are: 1.when in stop and go traffic temp guage climbs above half-way mark but not to the red...this fluctuates when I drive a good distance back down to 185 deg. f 2. I can run the defrost (hot in winter or air conditioner during the summer) and the temp will not fluctuate as bad. 3. If I run the defrost to keep engine at constant temp during the winter, the air is cold.
What I suspect and what I have done: (to no avail) I have flushed the cooling system out 3 times since purchasing vehicle in OCT 09.. including flushing the heater core seperate..In between the 2nd and 3rd flushings I replaced thermostat (185) and the pressure cap on radiator. I suspect heater core is stopped up still from the old dex cool. I have replaced the dex cool with universal green..I did that on the first flushing.. I check the level of antifreeze/coolant and the levels check out. This car only has 61000 miles on it and it set for a long time obiously. Any ideas or suggestions would help..Thanks

[wrightz28]

I'd check and make sure that the prmary fan is working, there is no debris inbetween the radiator and A/C condensor and that the air dam is in place for starters.

[magnum1968]

I done that, primary fan motor is good because it will run when defrost switch is on, and the a/c fan (which is seperate) runs when a/c is on.. checked my 3 relays , they are good...put the car on a diagnostic and for some reason or another it seems my on board computer is not commanding the fan to come on. My temp sensors are good, and my guage is recording accurately. I looked for a broken or severed wiring ( where I could) and can't find anything....Looks like I'm gonna have to run a secondary switch to just manually control the fan when I'm in traffic. I hate that because it will decrase the value of my car. Any suggestions on the best way to do this? Thanks for the reply..

[wrightz28]

Ok, the ECM not comanding it to come on during diagntostic startup is concerning. Didn't catch in your reply tho, is it coming on at all? I'm not a fan of hack jobbing the fan either.

[magnum1968]

yea it runs when I switch on the defrost, this was verified by an ase mechanic... It just dont switch on when the temp requires it too. The a/c will run the fan too when switched on, so that eliminates the fan motor itself being shot....do you think I ought to mabe just replace computer with an updated one (this one is 15 plus years old)..thanks again for the reply...

[wrightz28]

Heh, I thought you have 2 fans, a primary controlled by the cooling fan switch/PCM, and the secondary that would come on when the A/C is signaled. Ok, if you have a single fan setup, same rule applies.

I've been out of the loop for a bit, so I don't remember off hand if the PCM commands the fan (supplies the ground) through the use of the CTS readings. But it just hit me, I do believe OBDI hybrids like yours still use a fan switch that is on the passanger side cylinder head?

[magnum1968]

switch is on the cylinder head...yes I have two fans, one is controlled by a/c (through relay) and the other is contolled by the other two relays (low speed/ high speed)

[wrightz28]

Have you tried grounding the switch wire to see if that kicks the fan on?

[magnum1968]

no I havent....good suggestion..I just can't work on car anytime soon because I have a med issue to deal with..Thanks for the tip...I'll try your suggestion (if I can find the wire) and check it when I am able...I'll be out for a couple of days.. BTW, I been running the car and using the defrost/floor selection and have had no issues in traffic she runs good n strong, and the temp holds around 185..what I don't like is all the jerks who like to mess with me when I'm operating my camaro.. it seems as though everybody (esp foreign cars) like to try and initiate a race...Guess I'll drive her as fast as my license can stand!!