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2 Posts
Discussion Starter · #1 ·
Hello all...first time poster, long time reader...

I have a 2004 2.0 NBC that I'm trying to recommission and it fights me at every turn...

So far I've had to completely replace the bonnet locking mechanism (inc. cable and pull, which was fun), the bonnet, boot struts, resolve roof operation issues, clean the interior, clean the front crash sensor contacts, and - most recently - replace the cambelt/water pump.

Latest issue is that as soon as I reconnect the battery the cooling fans run at high speed. Both fans - as soon as the battery is connected. The only way to stop them is to disconnect the battery.

I have:
Checked the external/ambient temperature sensor
Checked the AC switch is off
Checked the green thermo switch in the hose on the right hand side of the engine
Checked the big fuses in the battery-mounted fusebox
Unplugged the cable for the radiator mounted thermo switch

All with no difference. Unplugging sensors doesn't change anything, but I think I expected that it would fail 'safe'...?

So...I look to you for advice. Where do I go from here? I can't get the radiator-mounted (bottom right) thermo switch out, but will this control the on/off of the fans? Would that cause it? I've ordered a replacement green switch but putting a meter across the 4-pins shows the same results (for continuity) as the existing one (ie: continuity across two pins but none of the others).

Is the next step the bottom sensor/switch, or is it the FCM? Or is it likely to be the green switch anyway...? Or something completely different...?

Many thanks for any guidance! I'm a little perplexed by electrics 馃槅

5/23/10 <3
11,359 Posts

2 Posts
Discussion Starter · #4 ·
Just to follow up on this, I opened up the FCM to be met with a lot of rusty and fused together switches and contacts. I could clean them up but decided that a new module was the way to go which resolved the problem.

However鈥 week or so later I found the battery flat again. No fans running on this time so I put a meter across the battery to find a 3amp draw with the ignition off. I pulled fuses until the draw dropped to a more usual level (0.5ma I think) and the fuse that caused the drop鈥..?

Fan control module.

So, is it likely that the FCM on its own would cause a continuous 3a draw without rubbing the fans or might there be something else I need to look for鈥? Something potentially quicker than returning the FCM, getting into an argument as to whether it鈥檚 faulty or not, and either buying a replacement or waiting for a replacement to arrive鈥?

Thanks all.

15,626 Posts
What brand fcm did you buy; there are lots of cheap ones out there, like the notorious URO brand (I believe Stribel is the oem for VW). We have heard of the cheap aftermarket fcm's causing problems, defective out of the box and not working correctly.

This video; goes over testing strategies might be helpful:

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