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Help! 99 cooling fans run slow

kens99vette

Member
Joined
Mar 5, 2008
Messages
7
Location
florida
Corvette
99 navy met. coupe
My cooling fans on my 99 are not running and won't cool the car. Any suggestions would be greatly appreciated.
 
Replace both the fan motors AND the relays in the underhood fuse box that supply power to the fan motors. What happens is that as the motors age, their resistance slowly goes up. They don't actually fail... the relays overheat and fail. Then, if you just replace the relays, the fans will work but the relays will fail again shortly. Pull the primary fan relay out of the underhood fuse box and look for signs of overheating around the pins.

I don't know what the fan motors on a vette cost, but I was able to pick up replacements for my 96 impala for about $40 from the auto parts store. I had to order the relays from GM, they were about $40 apiece as well.
 
You can guess then buy new parts on a trial-and-error basis or...


...you can purchase a set of Factory Service Manuals and use the cooling fan diagnosis instructions to decide if the problem is the fans, the relays, the wiring, the connectors or the VCM.
 
You can guess then buy new parts on a trial-and-error basis or...


...you can purchase a set of Factory Service Manuals and use the cooling fan diagnosis instructions to decide if the problem is the fans, the relays, the wiring, the connectors or the VCM.

Or you could save yourself the cost of the manuals and just go out and pull a relay and look for signs of overheating.
 
You can guess then buy new parts on a trial-and-error basis or...


...you can purchase a set of Factory Service Manuals and use the cooling fan diagnosis instructions to decide if the problem is the fans, the relays, the wiring, the connectors or the VCM.

BINGO. The second smartest thing to do is learn how to pull your codes.

Or you could save yourself the cost of the manuals and just go out and pull a relay and look for signs of overheating.

First you suggest that the OP change the fan motors on his ride without knowing anything about the mileage on his car, any modification or recent repairs that may have caused the problem or what codes the car may be throwing. The fans on this car are not notorious for building up any kind of resistance and slowing down. The radiator will need replacing way before then. I'm coming up on 150,000 and my car runs cool as a cucumber. Second, you suggest he save himself the cost of the service manual. Not very solid advice given the service manual was written by the guys who designed the car from the ground up.

This ain't no Impala we're talking about here.

To the OP (if you are still experiencing this issue), start by pulling your codes. When trouble-shooting this car, you don't turn 1 bolt without seeing what the car is trying to tell you. Like Hib, I'm going to highly suggest you buy the service manuals for this car if you plan to work on it. There's nothing more frustrating (and frankly, stupid), than working blind. When you pull the codes, you are going to be looking for DTC's 0480 and 0481 in particular. Also, check MaxiFuses 48 and 49, along with MiniFuse 14. There's also Mini Relay's 43, 44, and 45 which play into the equation so they will also need to be checked.

Work smart my friend. Arm yourself with the necessary tools and information to be successful. :thumb
 
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You can guess then buy new parts on a trial-and-error basis or...


...you can purchase a set of Factory Service Manuals and use the cooling fan diagnosis instructions to decide if the problem is the fans, the relays, the wiring, the connectors or the VCM.
:thumb:thumb
BINGO. The second smartest thing to do is learn how to pull your codes..
:thumb:thumb


Or you could save yourself the cost of the manuals and just go out and pull a relay and look for signs of overheating.
:hb :hb

First you suggest that the OP change the fan motors on his ride without knowing anything about the mileage on his car, any modification or recent repairs that may have caused the problem or what codes the car may be throwing. The fans on this car are not notorious for building up any kind of resistance and slowing down. The radiator will need replacing way before then. I'm coming up on 150,000 and my car runs cool as a cucumber. Second, you suggest he save himself the cost of the service manual. Not very solid advice given the service manual was written by the guys who designed the car from the ground up.

This ain't no Impala we're talking about here.



To the OP (if you are still experiencing this issue), start by pulling your codes. When trouble-shooting this car, you don't turn 1 bolt without seeing what the car is trying to tell you. Like Hib, I'm going to highly suggest you buy the service manuals for this car if you plan to work on it. There's nothing more frustrating (and frankly, stupid), than working blind. When you pull the codes, you are going to be looking for DTC's 0480 and 0481 in particular. Also, check MaxiFuses 48 and 49, along with MiniFuse 14. There's also Mini Relay's 43, 44, and 45 which play into the equation so they will also need to be checked.

Work smart my friend. Arm yourself with the necessary tools and information to be successful. :thumb


smiley4.gif smiley4.gif smiley4.gif :thumb

And I'd like to add #3
Never under estimate the ingenuity of a Idiot,He was probly there before you!~!!:chuckle

attachment.php


:beer
 
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You da' man Jesse! :BOW :thumb
 
Gentlemen this is my first post on this forum so Hello. I experienced some issues with my 2000 vert that you all may be interested in. I had the car die on me at an intersection but then start back up. This happened a couple of times until it would not start or only start and idle around 400 rpm. I went out to the fuse box by the battery and all I did was pull the fuel pump fuse, it was good, and re-installed. Then I pulled the fuel pump relay, the contacts looked good and just re-installed. Got in the car and turned the key on, I heard the fuel pump pressure up and the car started no problems, and has ever since. I also was having issues with my cooling fans kicking on and off when I had the air conditioning on. I suspect the fans were not running normally and the head pressure on the a/c was going high and then the fans would kick on all at once until the head pressure came back down and then they would kick off again. I did check and the compressor was not cycling when this was happening. I pulled all 3 fan relays, cleaned the contacts and re-installed. When I started the car and turned on the a/c after cleaning the relays the fans came on in the low speed as they should and did not cycle anymore. Everything at that point worked as it should from the factory. I said all of this to say that the relays and the fuses in the fuse box by the battery appear to be causing some high resistance from being in the car for this many years and causing some aggravating electrical issues. When I pulled the fuses and relays there did not appear to be any notable corrosion on the spades but again cleaning and re-installing seems to have fixed the problems I was having. Good luck and I hope this helps.
:w
 
Correction it looks like I have posted a couple of times before ( memory just is not what it used to be ) Hello anyway. :L
 
Hey Orange, thanks for the input. I too have seen similar issues with contacts appearing to be fine but causing issues. Those electrons can be finicky sometimes as I found out in my years at Motorola repairing circuit boards. Your situation is one that I will keep in mind. Thanks again for chiming in. :thumb
 
No problem. You are right, electons can be finiky sometimes. I just hope the post helps someone.
:beer
 

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