What is this fuse for?

[<3Quattro]

There is a 60 amp fuse under the dash in my 2002 b6 1.8t. it's melted into the fuse holder for some reason and I'm having issues with my radiator fans not switching on. Can anyone shed some light on this and what this fuse is for? Cheers.

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[Nollywood]

That fuse is for your fan controller / aircon. You need to start looking at a short to ground in the engine bay, and corroded / dirty connections. Dirty connections will cause the fuse to run hot, before it burns out, melting the plastic holder.

[<3Quattro]

Would this affect my fans not turning on

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[5ktq]

Problem is probably downstream, fcm or fan, wiring. Melted fuses are generally symptoms, not causes

[thomastollar]

This would def. cause your fans not to run...I had the same problem. The 60amp in my car fried because I had a leak coming in through the ECU.

[<3Quattro]

Now even though my fuse was melted I still had 12v going to the connecter to the fcm and my fans weren't still working. Would this melted fuse affect the average perhaps causing them not to turn on. On a side note it definitely looks like moisture caused this. The leads before the fuse holder were severely correded and my gasket to the ecu box is buggered.

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[<3Quattro]

The amperage is what I meant to say

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[thomastollar]

Have you checked the fans independently of the FCM? Also your fan relay in the ECU...I believe it is #219?

[<3Quattro]

Relay seemed fine. I jumped the fans to a 12v source through the connecter before the fcm and they turned on only with reverse polarity though. I am confused. Electrical is not my strong suit

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[old guy]

Relay seemed fine. I jumped the fans to a 12v source through the connecter before the fcm and they turned on only with reverse polarity though. I am confused. Electrical is not my strong suit

With DC (direct current) the polarity changes the current flow direction. Swap the wires and the fans will turn in the opposite direction.

[<3Quattro]

And I learned something new today. Awesome thanks :)

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[<3Quattro]

Well from what I've read so far the majority of issurs that arise with the radiator fans are because of the fcm or the thermo switch. I'll get a new fuse holder and fuse first and see what happens.

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[<3Quattro]

No luck with the new fuse holder. Looks like the fcm will be getting replaced next. Fingers crossed

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[<3Quattro]

So I replaced the fcm today. The fans still won't turn on on there own at idle. They turn on now with the AC. When I turn the heat on which I'd weird no? Also they will turn on when I take the thermo switch plug out. Any ideas ...

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[imnuts]

Is the engine at temp when you're checking the fans? They aren't going to turn on with a cold engine just because you're idling, and it may not even come on with the engine warm depending on weather and coolant temp. Coming in with the AC is normal though.

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[<3Quattro]

Engine was idling for a long time. Needle was in the middle of the gauge.



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[<3Quattro]

Shouldn't only one fan turn on when the AC is activated ? Both my fans were running full blast. Any help appreciated

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[5ktq]

little one is for AC, big one is for engine

[<3Quattro]

Should my bottom rad hose be cold? Fans only turn on now when I disconnect the fan switch on lower rad hose.

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[<3Quattro]

Also after idling for awhile my rear coolent flange leaks and it's brand new with a new oring what gives? Ahhh so frustrated!!!

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[diagnosticator]

Engine was idling for a long time. Needle was in the middle of the gauge.



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With the temp gauge at the middle of the range, the engine temp is already controlled without the radiator fan running. There is enough heat removed from the coolant by convection and radiation from the radiator to control the coolant temperature below the temperature required to activate the radiator fan ON, and is enough cooling to at idle without the fan running. Especially if the cabin HVAC is in heating mode, because the heater core is a mini radiator. During cold weather, with the heater turned up to full blast hot, there is often enough cooling of the engine coolant as it heats up the cabin interior to satisfy the entire cooling requirement of the engine at idle speed.

[<3Quattro]

Hmm okay. I'm just concerned because I keep getting random leaks in the cooling system after the car is running for awhile at idle. I assumed that maybe there is.more pressure in the system and this is causing the leaks becaue the fans are not turning on. I am just a driveway mechanic with not a whole lot of knowledge. I just get by.

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[diagnosticator]

Hmm okay. I'm just concerned because I keep getting random leaks in the cooling system after the car is running for awhile at idle. I assumed that maybe there is.more pressure in the system and this is causing the leaks becaue the fans are not turning on. I am just a driveway mechanic with not a whole lot of knowledge. I just get by.

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The cooling system pressure depends on the temperature of the coolant. It will be higher when the coolant is hot enough to activate the cooling fan compared to the operating pressure when the coolant is lower than the temp required to activate the cooling fan ON. This is the case regardless of if the engine is idling while stopped, or driving down the road.

System leaks due to rigid defects in the cooling system joints like pin holes through metal fittings from corrosion, will get worse as the cooling system temperature and pressure increases to the rad fan ON temp, with the rate of coolant loss varying with the differential pressure between the inside of the cooling system and the outside ambient air pressure.

Frequently, coolant leaks are the worst with a cold cooling system, and the leaks slow or stop due to thermal expansion of the cooling system parts as the coolant warms up from cold, that tightens the joints in the system.
Leaks from the system when cold and briefly after cold starts before the system is up to operating temp, are usually due to loose hose clamps and O rings that are collapsed and don't provide enough sealing pressure when the coolant is cold.

[<3Quattro]

Thanks for that really good explanation. Now as for my brand new rear flange leaking could it just be a flawed part or perhaps the oring didn't seat properly?

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[<3Quattro]

To ad to this maybe a air blockage could cause this but I don't think I have one. Heat blows really hot. Again thank-you to all any help is greatly appreciated the topic is so off haha

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[diagnosticator]

Thanks for that really good explanation. Now as for my brand new rear flange leaking could it just be a flawed part or perhaps the oring didn't seat properly?

The head surface where the flange bolts up, could be corroded and pitted, causing failure of the O ring to seal properly. Or, the O ring popped out of it's grove and is pinched between the flange and the head.

To ad to this maybe a air blockage could cause this but I don't think I have one. Heat blows really hot. Again thank-you to all any help is greatly appreciated the topic is so off haha

You are welcome! Good luck fixing the leaks.