Cooling fans do not come on unless the A/C is engaged

SUZYPOLICE

MEMBER
1999 OLDSMOBILE INTRIGUE
3.8L
6 CYL
AUTOMATIC
180,000 MILES

I have the vehicle listed above GL, I just inherited it from my late roommate. I put in a new water pump a new power steering pump new rack and pinion replace the thermostat in the thermostat housing and I'm having the issue with the fans still not coming on. Did a radiator flush. I troubleshooted by checking to make sure there's no shorts in the wires. The fans come on when the air conditioner is engaged, but not any other time. I believe that the temperature control unit is part of the fan which I cannot afford to replace at this time especially since I know that it does work. I realized today that the temperature indicator inside of the car, on the air conditioning unit control board, says that it's 52 degrees outside when it's actually 82° outside. I'm wondering what, if anything this has to do with why my fans don't come on. I'm a woman without anybody to help me with this and I've been using the repair manuals to get me through to this point, but I could really use some good advice from a good mechanic. Please let me know if anybody has any idea of ways I can troubleshoot and finally fix these problems. As I was just looking in the fuse relay area, I noticed that the fan relay is supposed to be 40-amp fuse, but it was a 30-amp fuse. So, I have replaced it and I'm wondering if this could fix it or if there could have been a reason why someone put a 30-amp and a 40-amp spot that I'm not thinking of? Could this cause a problem for me because I've now put a 40-amp fuse in?

Thursday, September 30th, 2021 AT 5:47 PM

1 Reply

JACOBANDNICKOLAS

MECHANIC
110,176 POSTS

Hi,

Is the engine temperature gauge working? Also, there are two fuses related to the cooling fans. Cooling fan 1 is the 40 amp. Cooling fan 2 is a 30 amp. Make sure you have the correct fuses.

Also, when checking a fuse, it is not only important to confirm the fuse is good, but also you should check to make sure there is power to and from them. I suggest doing this as well. Here is a link that shows how it's done:

https://www.2carpros.com/articles/how-to-check-a-car-fuse

Next, I attached the wiring schematic for the cooling system below so you can see how power makes its way to the fan motors. Please keep in mind, one of the two fan motors could be bad. You can try running a jumper wire straight to the fan motor to see if it works. You will need a long enough wire to reach from the battery to the motor.

Also, note there are three relays in the under-hood fuse box. I would also check them as well. If there are other relays with the same part number, switch them to see if it makes a difference. If there isn't, here is a link that shows how to test a relay.

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

Check these things and let me know what you find or if you have other questions.

Take care,

Joe

See pics below. Note: I had to cut the wiring schematic in half to make it readable for you. I did overlap them so you can follow from one to the next.

Also, pic 3 shows the fuses and relays to check in the under-hood fuse box.

Images (Click to make bigger)