I know I have seen this before but couldn't find it. I have a 1991, L98, auto, and it appears the primary fan isn't coming on. According to the service manual certain parameters need to be met which my scan tool say are there, such as coolant temp., etc. Also, when met, turning the air on usually will immediately turn this on, but now there is nothing. Is this something as easy as the fan relay? I know there are two relays on the drivers side of the radiator, one is the primary, the other is the secondary fan relay. I have not removed any grounds, and they were working when I put the car away last fall. Any suggestions would be appreciated, THANKS!!

 

I'm surprised the FSM doesn't have a trouble shooting chart, but it's nothing more than common sense. Have you tested the fan motor to see if it operates? Have you tested the primary fan relay to see if it operates? Checked the wiring for continuity? Shorts? Disconnected plugs? If you'll LOOK, you'll find the problem.

RACE ON!!!

 

Thanks alot.......... I'll loooook, when I have time!

 

Check the ground signals into the relay(s) with a test light. I don't know the details on 89, but the ground signals that go to the relay to control the fans tend to be on the green wire.

 

Don't hurry on my account. Your welcome.

RACE ON!!!

 

Since you could get the fan to run with the a/c on previously and that does not work now, plus the fan activation standard conditions without a/c do not cause the fan to activate, I'd guess 1) the relay, 2) fan motor, 3) wiring. Working smarter not harder requires testing the easy cheap stuff first.

Most of the relays on the 88-91 L-98 C4s were all the same as the main fan relay. According to my GM Parts Guide, your MAF power relay and blower motor are the same part number as the fan relay - GM# 14089936. You should be able to swap the main fan relay with another relay to test it. I bought one new relay as a test unit for my 88. Whenever I suspect a relay, I swap in the known good one and run my test. When I do find a bad relay, I already have the replacement in hand and don't need to make a trip to the auto parts store. For a one-time cost of $11 (NAPA), I don't have to break out the VM and test every wire to the relay to discover that I have a bad relay. I consider the known good relay as a cheap relay test tool. I just make a note to go get a new relay test tool the next time I'm out. If the relay tests ok, then there is no getting around the fact that I do have to break out the the VM and find the wiring diagram in the FSM.

If the relay test doesn't solve the problem, then I'd get the VM and FSM out and see if you are getting power to the relay. If relay power is ok, you need to ensure power to the fan from the relay. If you apply power to the fan and it activates, you have a wiring problem.

I assume that you double checked ALL the fuses first.

 

Thank you.

 

It was the fan relay....and not to start a flame war, but, I come on here with a question when I need to!! That doesn't include one or two word comments to increase my post count. I don't appreciate sacarastic comments regarding check this, do that, and otherwise stating the obvious, and then telling me to just LOOK. This was the first response I got after my initial post, which rather disturbed me. I was just trying to save time if someone had seen this issue before. If the one individual in question read the post, it was simply regarding the fan relay, which in fact was the problem. I could really care less about this individuals 8000 posts, that is irrelevent to me..... I have other responsibilities in my life that are more pressing then being on the internet for hours on end. I sincerely appreciate the other professional comments I got from the additional forum members!! Thank you!!!

 

You asked if it could be the relay. I responded to check the motor, the relay, and the wiring, in that order. That was pretty basic, and except for being somewhat less verbose, pretty much the same as other responses, you DON'T criticize.

It was rather disturbing to me that one could even ASK, what is so obvious. Breathe in...Breathe out...repeat as necessary.

RACE ON!!!

 

Thanks for returning to tell us what the solution was.

 

I would expect no less from Mr. Goodwrench, oh I mean, EFI-CFI!!! I'm sorry I bothered you with my trivial question, next time please just don't respond. By the way, do you have a 1991 Corvette that would make you such an authority on this particular car? Reading some of your other posts it appears that other people don't appreciate your comments, but hey your the main post guy with over 11000 posts, so what I could I possibly know? Looking at your profile I see no name, no profession, and a general location as to where you live. I guess it is safe to assume that you aren't an ASE Certified Technician. I'm rather surprised that the Moderator doesn't suggest that you tone your responses down just a bit......

 

On your next post, title it:

"Please help me with this problem (unless you are CFI-EFI)"

 

Damn! You have credited me with 3000 posts (11000 - 8000) in less than an hour and a half (5:02 PM - 6:26 PM. "what I could I possibly know?" Indeed!

RACE ON!!!