Is my pass. side fan supposed to come on as soon as the AC is turned on, or does the engine temp still have something to do with it ? As far as I can tell, it never comes on. It's a 95 model, with a few mods, and a tune by PCMforless.
I just put a new water pump and opti on, and while it runs cooler at speed, it heats up when sitting in traffic. It will get to 215 to 221 at slow speed or idling. Air temp in the mid 90's. Once I can get it crusing it will slowly get back down to 197. No difference with AC on or off.

 

Sounds normal as far as temp. Fan switch on compressor may be bad.

 

At least on my 93...

Main fan at 220 ish. second at 235.
BOTH all the time with A/C on.

All of this is controlled by the computer.

First thing I'd do (cause it's easy) is swap the connectors on the fan relays. This will verify the relay is good.

The relay's have an "internal schematic" printed on the top of the case. They are energized when the computer "grounds" the ground side of the coil. Use a jumper to connect that (coil ground) wire on both relays together. Then when one fan turns on the other will too. This will verify the fan itself.

If it works, nuttin left but the computer.

It is perfectly safe to permanently connect those 2 wires to get both fans to work.

 

Both my fans come on when the AC is turned on. Did you plug the relays back in? Check to see if one is loose. When I did my radiator swap I forgot to plug one back up or it came loose. I found it later on.

 

A/C fans for '90 and up are controlled by a Sensor (Presssure) mounted on the high side or smaller line from the Condensor to the Evaporator. It's a 3 wire thermistor (signal rises with pressure) with a 5 volt reference from the ECM/PCM, a return and ground. Each return volt is about 100 psi. For most systems (see your Service Manual for actual specs) the ECM/PCM is going to ground the Main Relay with a 2 volt return or about 200 psi. The secondary will be grounded if the signal rises to about 2.3 volts or 230 psi. The '96 even bumps the secondary rpms up depending on that signal.

What's happening at the Condensor is actually a heat exchange (High Pressure gas being changed into a High Pressure Liquid) and it builds heat (pressure) a zillion times faster than anything going on with the cooling system. That's why the fan(s) will come on well below any temp programmed for non a/c operation and that's one of the reasons you car has a thermostat (with a/c operation it would take forever for the coolant to warmup). The condensor is also mounted in front of the radiator as the high side needs to average around 200 psi which is below 150 degrees.

If the cooling system is clean and the a/c functioning correctly, you should see a couple to 10 degrees better, at idle with the a/c on because the fans will always be cranking (at least if it's 50 degrees better out). High a/c coolant temps are usually because the system is plugged up - more pressure more heat; overcharged - same deal - or airflow is restricted. Check it out by scanning it which will give you the pressure signal in volts and pressure while you watch what the fans are doing. Further diagnostics require a manifold gage set, but as a rule of thumb, if the high side on your scan shows a pressure that is greater than 2.5 times the air temp at the condensor, it's got a problem (ie, if it's a 100 degrees at the condensor, the high side shouldn't exceed 250psi - note bottom feeders like the Vette often have a higher air temp at the condensor when stationary). As a side note, because it has to run cooler than what it needs for good emissions control, a/c operation is exempt from the regs - so if you want to flaunt the law, just keep your a/c cranking.

 

Wow. After that last post, I'm embarrased to tell what the problem was. I got it into the garage and jacked it up to look as suggested. The fan was unplugged. I don't know how long it has been off, I didn't do it. Thanks for the help, both the simple suggestion that fixed it, and the post on how the system works. Good reading.