Air Conditioning / Fan Issue. 02 GTI

[punisher89]

Sorry, I searched but so much stuff doesn't get picked up because A/C doesn't come up in Search.

Well, it's October and I live in South Hell so naturally it's still in the high-80s at night and my A/C took a dump. It worked fine on the way to work but it didn't on my lunch break, press the button, light comes on and nothing happens. The fans don't kick on at all, the compressor doesn't engage, the air doesn't get cold, nothing.

The compressor was replaced about 18 months ago and I think the problem is electrical but I don't know much about A/C so I'm kinda stumped, I'm also broke so I can't go throwing money at the problem.

Any help is appreciated. Thanks.

[Scigano]

I'd begin by looking at the fuse box on the top of the battery. The middle of the three fuses is responsible for controlling the engagement of the fans. If something spikes the voltage in that circuit, it can take out the fuse — disabling your fans (and the A/C compressor by association, I'll get to that in a moment).

When the A/C is on, the first of the fans's two speeds are constantly running when the car slows down to a certain speed, or stops altogether. This is to keep the compressor cool (it generates buku-heat n' could burn itself out otherwise).

If that fuse blew, the car was designed to not operate the compressor if the fans were inoperable (for fear of compounding the issue w/ a broken compressor — also, your A/C being out is a good way of letting you know this may have happened). When your car is at risk of getting hot (which it will without properly working fans), so will you.

If it isn't the fuse, the next likely culprit is the fan control module below the battery. This controls all functions of the auxiliary fans. I'd bet a nickel or two that if you pop that fusebox cover on top of the battery, you'll find a toasted fuse though.

If you do, that doesn't necessarily mean that's the only thing that needs replacing (by the way — if the fuse burnt out spectacularly enough, the whole battery-top fuse panel may need replacing). The spike in electricity could damage the fan control module too — in fact, any electrical device connected to that circuit could be at risk of damage if voltage spiked.

When this happened to me, I ended up having to change the fuse box on the battery, the fan control module beneath it, and I even changed the fan thermal switch (located in the passenger bottom corner of the radiator). The fans themselves appear to be working properly, so I lucked out there.

After you replace what ever's necessary to get the fans to kick on again, keep an eye on the coolant temperature, and it may not be a bad idea to make sure too much voltage isn't being pulled by the electrics of the cooling system — just to make sure there wasn't something else that caused the original parts to burn out in the first place, and will toast the new ones too.

Good luck, cap'n.

[punisher89]

I looked at the fuse box on top of the battery, according to the bentley the fuse is question is the farthest to the left and is yellowish-lime-greenish in color. It wasn't scorched or melted but when I pulled the fuse one of the prongs has some black sut on it and the slot was slightly melted, I imagine that is the issue. I'm going to try to replace that fuse and see if it fixes the problem.

Also, is there any correlation between the heated seats and the A/C? I've used my heated seats exactly twice, the last time my compressor went (I didn't notice as quick as it was in the cooler months) and then this week, I used them monday night with the A/C on (for the girl) and tuesday afternoon I had no A/C.

[Scigano]

Ooo — regarding that, I don't know. I'll bump the thread up so someone else can see if they know (I don't think they are though — that could have been coincidental and it was just the fuse's time to go).

If you replace the fuse and the fans still won't kick on, the whole fuse box may need replacing if the voltage damaged the panel itself (you said it was slightly melted at the slot). If you replace both of those and the fans still won't kick on — the next thing to look it as is the under-battery fan control module.

[punisher89]

Replaced the fuse, it worked. Which makes this the single cheapest repair in the 14 year history of me owning VWs.

My only worry is why did it go in the first place and if it goes again, what might be the cause?

[Scigano]

Something within the cooling system circuit may have pulled too much voltage and spiked the whole system. The way my boy at the shop checked after we discovered the fuse panel issue was checking the fans with a temp gun to see if they were getting unusually hot (from a cold start or just running the fans with the ignition on n' A/C engaged).

If the temp just kept climbing and climbing instead of holding steady, we'd assume electrical bits were about to fry again — but luckily didn't. We only had to keep an eye on the fan packs because they were the only cooling electrical item I hadn't changed when the fuse blew in the first place.

The fan control module, fuse box, and new fuses were all in. Even changed the fan thermal switch. All of that had never been changed before I think (and it is a 12-year-old car). If nothing else, maybe that fuse just couldn't hold current anymore after years of doing its job. It could be that simple.

Your spike didn't seem that hard if the fuse panel is okay (and so's the fan control module, the fans, and everything else apparently). Keep and eye on your temperature. If it holds steady and true for a few days later, chances are you're good.