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Discussion Starter #1
Hey all I am trying to locate and test my coolant temp sensor though can not find it anywhere. My fan stopped working and I would like to trouble shoot the problem and was told this is the place to start.

I also have no idea where the sensors hanging down go to. I bought this used recently and am trying to put everything back in order.

The car is a 2001 alh.

Many thanks.

I noticed I could not find a photo of the sensor online so hopefully this thread will help some people in the future.
 

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That thing hanging down is likely for the thermometer on your mirror and should be in a clip on the inside of the bumper.

The coolant sensor is near where you are looking, however you'll need to get the car up on ramps and pull off that side skirt, not just the bottom pan in order to reach it and test it easily.

The sensor is above the lower radiator hose/drain. Number 21 on this image.
 

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Discussion Starter #4
Here is the set up to test low speed which did not work. The next post will show the high speed fan test where the ignition key has to be on. For this test of the low speed fan the ignition key can be in the off position though I could not confirm this as on my car only the high speed fan worked.
 

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Discussion Starter #6
I read the high speed is hard wired and does not go through the FCM so this is probably bad I would say. My car did over heat the other day with the ac on. Would the high speed cool things down? If this is the case would this mean the coolant temp switch is also bad?
 

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Discussion Starter #7
I am wondering if the water pump impellar could have broke. To check for coolant flow, on the coolant bottle there is a small bypass hose that comes into the top of the bottle with the car running there should be coolant flow through this hose into the bottle, this will cause the engine to over heat and the fans not to come on, as the coolant temp sensor for the fans is located on the radiator tank. If this is the case I want to test it though do not know if water will flow into the bottle with a cold engine or not. Does the thermostat need to open and if so how long would it take to warm up. I notice when I start the car there is a blue light indicting the engine is cold. Once this light goes off does this mean the water should be flowing? Could the thermostat be seized shut instead of stuck open?
 

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Discussion Starter #9
I have not replaced the coolant sensor yet. The only thing that is leaning me towards the fan control module instead of the sensor itself is when I jumpered the electrical plug that connects to the coolant sensor the low speed fan did not come on. If it was only the switch this should have got the fan turning. I am going to pull the fan control module and see if one of the three contacts is stuck or otherwise burnt out. Here is a cool video about the inside issues of the fan control module VW A3: Coolant Fan Control Module Autopsy (for lack of a better word) - YouTube
 

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I have not replaced the coolant sensor yet. The only thing that is leaning me towards the fan control module instead of the sensor itself is when I jumpered the electrical plug that connects to the coolant sensor the low speed fan did not come on. If it was only the switch this should have got the fan turning. I am going to pull the fan control module and see if one of the three contacts is stuck or otherwise burnt out. Here is a cool video about the inside issues of the fan control module VW A3: Coolant Fan Control Module Autopsy (for lack of a better word) - YouTube
Yeah, it will be visibly obvious if the contacts are burnt. Hopefully your troubles stop there.
 

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Sounds silly, but have you checked your fuses located near the battery? I had the same problem.

When you turn the ignition to the on/run position (with the engine not running), then turn the air conditioning on - both the rad fans should run. If not - more than likely it's a blown/burnt fuse. They're located above the battery. Mine happened to be pretty melted - a couple new fuses and I was good to go.

Just a thought...

- Adam



 

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Discussion Starter #12
I have checked the uses and they seem to be in good order. Thank you :) I will update when I have further time to diagnose. Next step is removing the FCM.
 

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Discussion Starter #15
Well I am not getting anything anymore when I jump the socket to the coolant temp switch now. I was getting the high speed to turn on so I am thinking there must be a wire loose or some thing. All the fuses above the battery look fine. I am stumped for tonight.
 

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Discussion Starter #16 (Edited)
Okay so the results are in. Good news I found a problem though I suppose that is also the bad news in this case.

I jumpered both fans. The larger one came back with nothing for high or low speed. The smaller one seems to work on high. I say high as it was fairly loud. The curved end of both plugs was the ground. The far side inlet I believe to be the high speed.

Now the trick is finding one in Guatemala
 

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5/23/10 <3
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As posted in another thread, don't buy from hansautoparts. There is a reason their prices are so cheap...its all garbage.
 
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