'99 GAGT: Cooling fan fuse blows again!...Why? [Archive] - GrandAmGT.com Forum

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Turismo
07-01-2004, 12:31 AM
I have blown the blue 30A fuse located in the fusible link under the hood that controls my cooling fan. This has occurred several times this summer under normal driving conditions and, of course, results in escalating engine temps. Anyone encounter this problem?

Dan00GPGT
07-01-2004, 07:51 AM
I see two 30 amp fuses listed. Both are underhood but one is labeled COOL FAN 1 and the other is COOL FAN #2 GROUND. Which one is blowing? If I had to guess, I'd say one or both of your fans is drawing a little too much current and popping that fuse. There aren't any specs on checking the fans in the service manual. Your fans operate in high and low speed modes. When they are in low speed mode both fans are in series and run at a slower rate. When they are in high speed mode the circuit changes and both fans run at full speed. When the fuse blows, does one fan work and the other fan doesn't? If so, then the fan that ISN'T running is most likely a little light on the internal resistance and is the cause of the fuse popping.

I'm not sure if you can replace one fan or the other or if they are a unit. The next time one of them goes, check which one is still working and then replace the opposite one.

Turismo
07-01-2004, 11:52 AM
Fuse Relay Center (underhood):
#8 = Cooling Fan (large, green, 30A, PAT. 4604602-4635023)
#52 = Cooling Fan (small, blue, 15A)

The numbers are from my owners manual and #8 is the one popping. #52 is in good condition and has never been replaced.

In a normal situation my fans maintain 90 degress celsius (194 F). Today I ran the car for awhile and then idled in park. The temp. went up to 94 C and neither fan came on, not even in low speed. I briefly turned on the heat and both fans were running. After I turned of the heat off, the fans were still running.

What do you make of this.

I will test you theory the next time the fuse pops. I replaced it last week and it has not popped yet

Dan00GPGT
07-01-2004, 03:04 PM
When you turned on the heat was the air conditioner on or did you have the window defroster vent on (automatically runs the ac compressor). The low speed fans don't come on until around 223 degrees according to the service manual. 230 degrees turns on the high speed fans.

Turismo
07-02-2004, 12:33 AM
No, the first thing I did was turn the heat on without the A/C or window defroster on. Both fans came on and continued running even after turning the heat off.

I will have to let the car idle longer and see if I can get it up to 223 degrees and determine if they come on or if the fuse blows at this time.

The first few years I had this car, 194 degrees was the norm. Now it seems to drift a little more and when it gets up to 220 or so, this usually means something is wrong like the fuse has popped. Sometimes this may be the case.

CelticSkyhawk
07-02-2004, 09:28 AM
I've had this problem for a while and can't seem to find the cause. I'm not blowing fuses, but I've got the same heating/non-cooling problem. I was told that I most likely have a bad fan switch, but I haven't taken the time to replace it as I'm not too sure where it is.

Dan00GPGT
07-02-2004, 01:46 PM
I've had this problem for a while and can't seem to find the cause. I'm not blowing fuses, but I've got the same heating/non-cooling problem. I was told that I most likely have a bad fan switch, but I haven't taken the time to replace it as I'm not too sure where it is.


The fan switch is just the engine coolant temp sensor. It communicates with the BCM which commands the fans on/off. If your gauge isn't working either then the ECT sensor is a likely cause. It's located in the thermostat housing on both engines (2.4, 3.4).

Turismo
07-04-2004, 06:55 PM
When the fuse blows, does one fan work and the other fan doesn't? If so, then the fan that ISN'T running is most likely a little light on the internal resistance and is the cause of the fuse popping.

I'm not sure if you can replace one fan or the other or if they are a unit. The next time one of them goes, check which one is still working and then replace the opposite one.

Ok Dan, here's the situation. The fuse popped tonight.

I didn't have time to let the engine heat up until 223 F (low speed). I let it idle for about 10 minutes and it hovered around 196 F, fans off. I turned on the heat and one fan came on. Same thing happens when I turned the A/C on, one fan comes on.

After replacing the fuse, with the engine around the same temp, 196 F, the fans were off as before but when I turn on the heat or A/C both fans come on as normal.

So do you think the fan that did not run when the fuse popped has some electrical short? It seems to take about one week for this problem to arise. Why does the other one run when the fuse is blown?

Dan00GPGT
07-06-2004, 09:29 AM
First, I'll explain how the fans run which may provide some idea as to what is going on with your situation. The fans are setup to either be off, both running slow, or both running fast. There should never be an instance where one fan is on and the other is not. One exception to that is if the #1 cooling fan fuse blows and the PCM is commanding a high speed cool condition. In that instance, the right side cooling fan will be running in high speed and the left side cooling fan will be off because the fuse is blown.

One thing I don't understand with your situation is that the fan is coming on when the heat is turned on. If you leave your car sit and it gets "cold" after the engine not running for a couple hours, turn the heat to the floor and move the heat dial to hot... the fan comes on? Just one fan? If so, something is screwed up because that shouldn't happen (according to the service manual).

Which fan does not run when the fuse pops? Are the wires going into the fan light blue and white or are they black and grey?

When one fan was running was that before or after the fuse blew?

Here is what I would try if you have a multimeter. Disconnect your battery and then disconnect both fan plugs. Take your multimeter set on resistance and plug the leads into the fan plug attached to the fan. Take the resistance reading. Measure the other fan and see if they are relatively close. If one of them ends up being 500k and the other is 45 ohms then you will know if one is drastically off from the other.

This is a strange problem since if a short was occurring it should be all the time. The only other thing I can think of is that possibly your wires may have rubbed through and movement is causing the fuse to blow.

Dan00GPGT
07-06-2004, 09:36 AM
Ok, I reread your explanation and let me make sure I understand. You noticed that the fuse blew last night so you checked the fans and only one was running. You then replaced the fuse and both fans would then run. Is that what happened or was only one fan running and THEN the fuse blew?

If it was the first case then that was correct operation because the high speed fan output was telling both fans to come on but only the right one could. The left fan didn't have a voltage source since the fuse was blown.

As far as why this is happening.... I would guess one of a couple reasons.

1. You have a rubbed through wire that is making a short occasionally.
2. Your left cooling fan is drawing right around the maximum amperage the fuse can handle and eventually it kills the fuse.

Turismo
07-06-2004, 06:11 PM
More information:

Cold engine, set dial to heat floor and turned on heat.....no fans running. So that is normal.

I talked with the dealership and the passenger side fan (small) deals with A/C cooling. The driver side fan (large) is the main engine cooling fan.

So now the problem is isolated from the fuse to the main cooling fan. I will try your internal resistance testing using a multimeter. I think we've narrowed the problem down to one of two things...either:

1) When the main cooling fan kicks over to high speed it draws too much amperage due to lower internal resistance and kills the fuse. In this case, the fan can be purchased seperately and costs $100 from the dealer.

2) Wires have rubbed through and are causing an electrical short in the link


Right now I am leaning toward problem "1" because like you say an electrical short should happen all the time. On the other hand the weather here varies alot and several days I only make short trips....perhaps the high speed mode don't come on as its not needed making it seem like the fuse blows once a week.

Dan00GPGT
07-07-2004, 06:47 AM
More information:

Cold engine, set dial to heat floor and turned on heat.....no fans running. So that is normal.

I talked with the dealership and the passenger side fan (small) deals with A/C cooling. The driver side fan (large) is the main engine cooling fan.

So now the problem is isolated from the fuse to the main cooling fan. I will try your internal resistance testing using a multimeter. I think we've narrowed the problem down to one of two things...either:

1) When the main cooling fan kicks over to high speed it draws too much amperage due to lower internal resistance and kills the fuse. In this case, the fan can be purchased seperately and costs $100 from the dealer.

2) Wires have rubbed through and are causing an electrical short in the link


Right now I am leaning toward problem "1" because like you say an electrical short should happen all the time. On the other hand the weather here varies alot and several days I only make short trips....perhaps the high speed mode don't come on as its not needed making it seem like the fuse blows once a week.


I think you're 100% on the right track. It's quite possible that the high speed mode isn't used as often and that is what's killing your fuse. When the fans are run in series they aren't drawing the full current. When that primary fan switches to full speed it may be drawing the current that is killing the fuse.

Turismo
07-24-2004, 11:31 AM
I think you're 100% on the right track. It's quite possible that the high speed mode isn't used as often and that is what's killing your fuse. When the fans are run in series they aren't drawing the full current. When that primary fan switches to full speed it may be drawing the current that is killing the fuse.

Do you have the specs on the engine cooling fan like resistance or amperage draw? Several people in the business think I should check the relay under the hood. If that isn't clicking over, the fuse will blow all the time

tenspeed
07-24-2004, 12:52 PM
Since you're popping fuses, you can assume that your drawing too much current. Either you have a short to ground or the motor is drawing too much.

Squirt some oil on those five year old motor bearings and see if it solves the problem.

Turismo
07-24-2004, 05:11 PM
I discovered something interesting today regarding this problem. For once we had a hot day so I decided to let the car idle and observe what happens. When the thermostat reached approx. 223 F both fans came on (low speed) and the temp. declined. The 30A fuse was still intact. This is normal fan operation.
I repeated this a few times and got the same result. Note: I never had the chance to test high speed mode as the engine would cool every time low speed kicked in.

On the fourth trial (after both fans were going) I turned on the heat and within 5 seconds the fuse popped and an off odor was noticed (probably wires overheating).

So the question of the day is when you turn the vents on (heat or A/C), does that command the PCM to turn the fans on to high speed? When the fuse popped the driver side fan stopped and the other fan seemed to be rotating faster than before.

CelticSkyhawk
07-24-2004, 09:40 PM
What speed did you turn the heat to? On my car, if I turn it to 1 or 2, the fans run in low speed. Any higher and they run high speed. You may have found your problem.

2000GA
07-24-2004, 10:02 PM
my high speed fans are always on when i put it in park to grab the mail or to go in the gas station with the ac on. i never had any fuses blow so you probably have a worn out fan and you should get it replaced.

Turismo
07-24-2004, 11:57 PM
What speed did you turn the heat to? On my car, if I turn it to 1 or 2, the fans run in low speed. Any higher and they run high speed. You may have found your problem.

Well actually my resistor block for settings 1 and 2 does not work, so I have to turn it to at least 3. But as far as I can tell when I set it to speed 3, the fans are really moving and this is the point where the fuse blows and the driver side fans stops.

Anyone know what the proper resistance is for the main engine cooling fan? Is it the same as the other cooling (A/C) fan? I will be testing it using a multimeter later today.

Thanks for all your help

Turismo
07-25-2004, 05:26 PM
Today I have pretty much isolated the fuse problem to the driver's side fan motor. Didn't get a chance to test the resistance as you have to remove the whole assembly to get at the terminals.

However, I disconnected the driver's side fan and turned the vents on without any problem (fuse popping). I also tested all three cooling relays, including the dual switching one thats responsible for engine cooling and they all "clicked" over properly when a magnetic field was produced.

All this testing leads me to a worn out fan motor...

Dan00GPGT
07-26-2004, 06:53 AM
Turismo, your fan has to be the problem. When your fuse blew the last time, most likely the AC pressure was higher than the threshold necessary to set the high speed operation in motion. When the high speed operation started your fan started to draw too much current, blew the fuse and shut off. The other fan got faster because it was in high speed mode and running independent of the other fan.

I could see one other possibility but if you're telling me that the fan runs fine in low speed mode then there's no way this could be true. Actually... unless one of your fans is constantly on there's no way it could be true. I was thinking you may have a short to voltage in the wiring between the two fans but that can't be true if your fans are both off at any point. Also, one of your fans would never run so forget that idea.

The relays not clicking over and completing the circuit have nothing to do with fuses popping. When the relay is energized, there is a coil that acts as a resistance to the circuit voltage. If the relay never "clicks over" then no circuit is completed and no current flows. If no current is flowing you can't pop a fuse. Whoever the people in the business are, they need to go and relearn basic 12 volt electronics or spend more time with the schematic. The relays are not your problem. :)

Turismo
07-26-2004, 10:08 PM
[QUOTE=Dan00GPGT]Turismo, your fan has to be the problem. When your fuse blew the last time, most likely the AC pressure was higher than the threshold necessary to set the high speed operation in motion. When the high speed operation started your fan started to draw too much current, blew the fuse and shut off. The other fan got faster because it was in high speed mode and running independent of the other fan.
QUOTE]

I agree. Even yesterday I was driving around in 90 degree heat all day and the fuse is intact all because high speed mode was never engaged. I never used the AC, nor did the engine temp ever exceed 230 degrees and low speed would cool the engine down before the higher speed was necessary.

As for the relay comment: If the fuse comes before the relay switch in a circuit and power is applied, wouldn't the fuse pop if the coil heated up and did not switch over?

This is why I come to these forums. GM techs tend to tell tall tales (say that 5 times quickly) just to sell there services. I learn alot more about my car from educated people online :)

Dan00GPGT
07-27-2004, 05:54 AM
When the coil in a relay is energized, it basically is creating an electromagnet. The switch is pulled closed and higher current can then flow through the circuit. Regardless of whether or not the switch closes, the magnetic field is created either way. There isn't a physical link between the two so it's not like an electric motor where strain and heat would be placed on the coil if the motor wasn't turning but voltage was being applied.

The coil in a relay is a high resistance and would probably burn up before the 30 amp fuse ever went. The coil side of a relay draws milliamps which is a fraction of an amp. If somehow you could cause 30 amps to go through a relay coil, you would most likely be replacing relays rather than fuses. :)

Hope that helps.