Cooling fans only work with a/c
 

Im a new member and a new to the world of Vette's.
I just bought a 98' A4 with 97k for $13.5k
I noticed when ac is off the fans will not come on, temp got to bout 230'ish. I turned ac on and sure enough fans came on and car cooled off. my digital and anolog gauges work fine ... is there another sensor responsible for the cooling fans? Thx ahead for any help:thumbs:

Standing still or moving? 230 is way to high with or without a/c! Your engine is fine even with higher temps but it is not good. A tuner can turn your fans on at lower engine temps with a few key strokes. A 160 thermostat and a tune will help! Might be a good time to flush and refill the radiator,,,,like me,,, your car will show some age. Fall will also help.

My fans come on at 190ish now, Never have seen 230 even after cam swap and outside temp above 110!


My $00.02

fans work fine as long as the ac is on. is there a seperate sensor other than temp gauge sensor that controls fans?

nice car btw

also who in okc area tune's vette's

That's an odd one. The fans are controlled by the same relays and PCM wiring AC or temperature only.

Are they spinning fairly "softly" with the AC on? They should be on low with both in series which makes them fairly silent. Confirm they are both turning too.

I believe the stock hi fan temperature is 236 degrees so you'd have to let the temps get that high to see what happens when the hi fans are called for.

Peter

I'll give it a try, I havent heard the fans on low, with ac they go strait to high ... maybe a relay and if so which one?

When the AC comes on the fans begin to run in high speed mode. If you are having trouble with low speed check the fuses first. My c5 through a dtc about low speed cooling fans not working and sure enough a fuse was blown. Search the forum for this problem and you should find information about what fuses to check and a handy wiring diagram that will show you how the fans operate. If the fuses are not blown I would check grounds or the relays.

Odd again, the fans should not run in high with the AC on. Take a good look around the under hood electrical center (the fuse block by the battery) and the wiring harnesses there and leading up towards the fans to see if something has been modified.


I don't believe this is correct. Mine run in low and I've read the posts here giving the service info which says the fans run in low with the AC on and the temps above 185 degrees. Here's the paragraph I copied which was posted as coming from the service manual:

The low speed cooling fan is commanded on when the coolant temperature reaches 108°C (226°F). It is turned off if the coolant temperature lowers to 104°C (219°F). The high speed cooling fan is commanded on when the coolant temperature reaches 113°C (235°F). It is turned off if the coolant temperature lowers to 108°C (226°F). When the A/C is on and the coolant temperature reaches 85°C (185°F), the low speed cooling fan will be turned on at vehicle speeds less than 56 kPh (35 mph).

Peter

Here's a thread with the fan wiring diagram;

http://forums.corvetteforum.com/c5-t...igh-speed.html

Peter

Here is a description of how the fans work and at what temps they are turned on and at what temps they go to high speed operation.
Cooling Fan Control
The engine cooling fan system consists of two electrical cooling fans and three fan relays. The relays are arranged in a series/parallel configuration that allows the powertrain control module (PCM) to operate both fans together at low or high speeds. The cooling fans and fan relays receive battery positive voltage and ignition 1 voltage from the underhood electrical center. The ground path is provided at G102.

During low speed operation, the PCM supplies the ground path for the low speed fan relay through the low speed cooling fan relay control circuit. This energizes the cooling fan 1 relay coil, closes the relay contacts, and supplies battery positive voltage through the cooling fan motor supply voltage circuit to the left cooling fan. The ground path for the left cooling fan is through the cooling fan 3 relay and the right cooling fan. The result is a series circuit with both fans running at low speed.

During high speed operation the PCM supplies the ground path for the cooling fan 1 relay through the low speed cooling fan relay control circuit. After a 3-second delay, the PCM supplies a ground path for the cooling fan 2 relay and the cooling fan 3 relay through the high speed cooling fan relay control circuit. This energizes the cooling fan 3 relay coil, closes the relay contacts, and provides a ground path for the left cooling fan. At the same time the cooling fan 2 relay coil is energized closing the relay contacts and provides battery positive voltage on the cooling fan motor supply voltage circuit to the right cooling fan. During high speed fan operation, both engine cooling fans have there own ground path. The result is a parallel circuit with both fans running at high speed.

The low speed cooling fan is commanded on when the coolant temperature reaches 108°C (226°F). It is turned off if the coolant temperature lowers to 104°C (219°F). The high speed cooling fan is commanded on when the coolant temperature reaches 113°C (235°F). It is turned off if the coolant temperature lowers to 108°C (226°F). When the A/C is on and the coolant temperature reaches 85°C (185°F), the low speed cooling fan will be turned on at vehicle speeds less than 56 kPh (35 mph).

People are always running around worrying about their temps because they see the numbers on the gauge. These cars are designed to work with high coolant temps and have no problems operating at the temps you indicate. As you can see the fans don't even get turned onto low speed until the temp hits 226 and don't go to high speed until the temp hits 235 degrees. At an autocross where we were running in heats and cycling through the runs quite fast I saw a 242 degree coolant temp on my C5Z for most of an event.

Bill

My 02 cooling fans come on but I can hear them when I turn on the AC. They work as avertised without the AC on coming on at 226 and turning off at 219. I don't know if they're coming on low or high when without the AC.

What fuse did you change during this?