About a month ago my cooling fan stopped running. I did not have the time to look at then I just went and bought a new relay and put it in but it did not help. I did try to ground the coolant fan switch like the manual said but no luck. I just always ran my a/c so it stayed on high. Now however a couple of days ago my a/c quit and so did the fan. I have checked the relays by the radiator and did replace 1 just because I bought it. I have jumped the ground on both to test and they work just fine. My blower in car works but the compressor does not work unless you jump the power at compressor. I have checked fuses and they are good so now I am guessing it might be a relay. I removed cover under steering wheel and I do not know which is which or even if this is the right location. The manual is not much help on this at all. Does anyone know or have pics? Am I on the right track? Any help on this or even where to check next would be greatly appreciated. This all started after I installed a hypertech inline chip. I don't know if it had anything to do with it but I did remove it today.

 

The 1994 has independently controlled fans (controlled by the ECM grounding one or the other or both relays mounted on the driver side of the radiator shroud based on ECT temperatures or AC pressures).

The digital dash temp is derived from the ECT (engine coolant temperature) sensor mounted into the front of the water pump.

The AC pressures are derived from the AC pressure sensor mounted in the high-pressure AC (smaller/lower) line near the fire-wall.

What are your digital dash temps?

Is there a chance the sensor or wire/plug is damaged or disconnected?

The fans operate differently depending on A/C being off or on.

When AC is OFF,

Primary (driver side) should come on at a digital dash temp of 228 F and go off once it falls back below 218 F.

Secondary (passenger side) fan should come on at a digital dash temp of 238 F and go off once it falls back below 226 F.

When AC is ON,

The above coolant temps still apply, however, AC pressure also comes into play (assuming air temps 70 F plus).

Generally within the first few seconds, due to a slight increase in the Freon pressure, the primary fan will come on.

Thereafter, generally within a few minutes, due to the AC pressure rising above a pre-set pressure (240 PSI +/-), the secondary fan will come on.

However, pressure is dependent on how hot the freon gets, so if your interior fan is not on or on low, or it is cool outside, both can prevent the secondary fan from coming on.

Also, low freon in the system can also prevent the pressure build-up and keep the secondary fan from coming on too.

Since you mention the AC is not working, its likely that you have a small freon leak and have insufficient freon in the system to build up pressure sufficient to engage the secondary fan.

The compressor will not turn on if there is insufficient pressure in the system (safetly feature -- controlled by the pressure sensor in the low-pressure (fatter) freon line near the fire-wall). BTW, that is a classic sign of insufficient freon.

For servicing the AC system, do a search for posts by SUNCR -- he's amazing at his knowledge of AC systems...

 

I had a problem similiar to this, but my issue turned out to be low freon. What threw me a curve is I bought a can of freon from Walmart and it came with this little guage. Turned out, the guage delivery line was faulty. The freon would not dispense. I bought a 2nd can with a more direct type of dispenser and it worked fine. Fan cut back on and the A/C turned ICE COLD! What a relief that it only needed freon.

Billy

 

Firstly the Admiral has laid well it out in plain English.

I am confused as you first indicated the fan stopped a month ago. Then indicated the fan quit a couple days ago (with the A/C).

The primary fan normally comes on with the A/C and runs only at ONE speed (no hi or low speed). So we might be dealing with 2 separate problems here.

If you have the C68 auto system, a low freon would cause a flashing green led. But usually if freon gets low cooling gets poor before low freon would be indicated.

I would suggest to jumper out the low pressure switch a see if the compressor starts. If it does not this would indicate more than a bad cycling switch or low freon. Depending on results we can go down either path.

Don’t know what book you are using to obtain your results about what points you are jumping out. Are you sure you are in the right places and making the right assumptions.

Have you ever tried to put 12 volts to the fan to see if it defective or measure the resistance of it.

And this hypertech inline chip you talk about. What does it do, where does it plug in how does it interface. This could through off normal diagnostic thinking.