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Volkswagen Passat: 1995-1997 (B4) Location of 3rd speed coolant fan control switch thermal switch?


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bill4

Posts: 31
Registered: 10/30/11
Re: Location of 3rd speed coolant fan control switch thermal switch?
Posted: Nov 8, 2011 8:48 PM   in response to: bill4 in response to: bill4
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Radiator is same temp throughout so thermostat must b ok
FKH161

Posts: 7,661
Registered: 12/29/05
Re: Location of 3rd speed coolant fan control switch thermal switch?
Posted: Nov 8, 2011 9:08 PM   in response to: bill4 in response to: bill4
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Thermo switch on rad should have at least triggered one speed, of not, replace thermo switch.

I'll see if I can find a test for the fan control module.

When a/c is selected, do the fans come on?

Sorry to keep running you around.
bill4

Posts: 31
Registered: 10/30/11
Re: Location of 3rd speed coolant fan control switch thermal switch?
Posted: Nov 8, 2011 9:21 PM   in response to: FKH161 in response to: FKH161
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Fan does not run when ac selected but ac has no charge.
No problem with runaround
so thermo switch is on top left corner of rad. Just making sure.
What is the switch on the lower part of the rad???
FKH161

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Registered: 12/29/05
Re: Location of 3rd speed coolant fan control switch thermal switch?
Posted: Nov 8, 2011 9:49 PM   in response to: bill4 in response to: bill4
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Not familiar with a second switch on the rad.... can you post a pic?



I only see one mounting hole for one sensor in the above image.

If you use the wiring diagram I posted earlier, you should be able to eliminate wiring issues to & from the module... in case I don't find something more specific during tv commercials.
bill4

Posts: 31
Registered: 10/30/11
Re: Location of 3rd speed coolant fan control switch thermal switch?
Posted: Nov 8, 2011 10:03 PM   in response to: FKH161 in response to: FKH161
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Just thought I read about a second sensor, but i dont see one on your pic.
ok What is the correct name for that sensor.
I am also running from my house to the garage to do the tests to figure out this problem.
But we will find the problem in time.
FKH161

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Registered: 12/29/05
Re: Location of 3rd speed coolant fan control switch thermal switch?
Posted: Nov 8, 2011 10:12 PM   in response to: bill4 in response to: bill4
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http://www.germanautoparts.com/Volkswagen/Passat/Cooling/208/4

Backspace the URL to find more catagories/parts.
bill4

Posts: 31
Registered: 10/30/11
Re: Location of 3rd speed coolant fan control switch thermal switch?
Posted: Nov 8, 2011 10:33 PM   in response to: FKH161 in response to: FKH161
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By jumping the fan switch on the rad and the fan working , would this not tell me that the module and wiring should be ok.
FKH161

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Registered: 12/29/05
Re: Location of 3rd speed coolant fan control switch thermal switch?
Posted: Nov 8, 2011 11:01 PM   in response to: bill4 in response to: bill4
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Not quite full verification.

If you only had high speed, then it could be that the resistors for low & medium speed were burnt out (inside the rad fan motor).

Since you can't have low speed if high speed were burnt out, that just leaves the control side of the motor... sensor or control module.
bill4

Posts: 31
Registered: 10/30/11
Re: Location of 3rd speed coolant fan control switch thermal switch?
Posted: Nov 8, 2011 11:12 PM   in response to: FKH161 in response to: FKH161
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So should I still get a thermo switch and replace it, or is more testing required.
Very green at this donot totally understand wireing diagrams.
I do really appreciate your help.
FKH161

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Registered: 12/29/05
Re: Location of 3rd speed coolant fan control switch thermal switch?
Posted: Nov 9, 2011 12:16 AM   in response to: bill4 in response to: bill4
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Not knowing the exact temp that the radiator got to... or how good the flow of coolant is through the system (thermostat opening, but not enough to allow full circulation), I can't say for sure what parts you need to buy.

I have seen thermo switches (in the radiator) with a layer of sludge/grime on the "sensing surface" that would prevent the sensor from getting accurate temp readings... removal of sensor for checking is a cheap place to start. Since the sensor itself is not that expensive, getting one from your local parts store may not be that bad either.

The Bentley info I have does not list specific tests for the control module, so I don't have anything further I can post on that.

According to the wiring diagram, low speed is the only speed that can run without the module (that's why it runs when you bridge the wire at the radiator thermo switch). It is also triggered by the module via the after-run temp sensor... that is why it runs when you shut the engine off.

It could very well be that you have a bad module, and since low speed does not activate on its own when the radiator gets hot, you most likely need the thermo switch as well.

I can't guarantee "what the problem is" unless I have my hands on it, sorry.

I know I mentioned fuse #19, but also check fuse #13 in the fuse / relay box.

Edited by: FKH161 on Nov 9, 2011 12:18 AM
bill4

Posts: 31
Registered: 10/30/11
Re: Location of 3rd speed coolant fan control switch thermal switch?
Posted: Nov 9, 2011 1:08 AM   in response to: FKH161 in response to: FKH161
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I checked all the fuses I could find by removing them and checking with an ohm meter all were good.
Will remove and check the thermo switch tomorrow.
bill4

Posts: 31
Registered: 10/30/11
Re: Location of 3rd speed coolant fan control switch thermal switch?
Posted: Nov 9, 2011 10:12 PM   in response to: bill4 in response to: bill4
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So i removed the thermo switch and it was covered in green crap.
I cleaned it off and hooked up an ohm meter to it and then used a small torch to heat it up.
I could not get a reading on the meter so the switch is bad.
Ordered one today and will get it tomorrow.
Will install it and let you know what happens.
FKH161

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Registered: 12/29/05
Re: Location of 3rd speed coolant fan control switch thermal switch?
Posted: Nov 9, 2011 10:22 PM   in response to: bill4 in response to: bill4
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Thanks for the update!
bill4

Posts: 31
Registered: 10/30/11
Re: Location of 3rd speed coolant fan control switch thermal switch?
Posted: Nov 13, 2011 1:12 PM   in response to: FKH161 in response to: FKH161
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So I put the thermo switch in the rad now the fan starts when it gets warm but only have low speed.
Is there anything else I can test for the other speeds
FKH161

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Registered: 12/29/05
Re: Location of 3rd speed coolant fan control switch thermal switch?
Posted: Nov 13, 2011 8:37 PM   in response to: bill4 in response to: bill4
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Attachment AcWiring.pdf (379.2 KB)
I have attached a full A/C wiring diagram... it will make more sense now with the A/C switches and power routing to the module.

If A/C doesn't work and you don't care about it, then ignore 3rd speed (high) operation, which is only used during A/C operation.

Depending on coolant temp, 2nd speed may not be needed if 1st speed keeps temp in check.

The module may be bad if second speed does not get triggered.
bill4

Posts: 31
Registered: 10/30/11
Re: Location of 3rd speed coolant fan control switch thermal switch?
Posted: Nov 13, 2011 10:21 PM   in response to: FKH161 in response to: FKH161
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What should the operating temp be
FKH161

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Registered: 12/29/05
Re: Location of 3rd speed coolant fan control switch thermal switch?
Posted: Nov 13, 2011 10:59 PM   in response to: bill4 in response to: bill4
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Around 90/95C 180/190F temp gauge in middle of travel.

The thermo switch you replaced should have temperature figures stamped on the metal portion.

The thermostat usually starts to open around 87c and is fully open by 100c.
bill4

Posts: 31
Registered: 10/30/11
Re: Location of 3rd speed coolant fan control switch thermal switch?
Posted: Nov 14, 2011 8:54 PM   in response to: FKH161 in response to: FKH161
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It stays around 100 - 110c I think this is ok
bill4

Posts: 31
Registered: 10/30/11
Re: Location of 3rd speed coolant fan control switch thermal switch?
Posted: Nov 14, 2011 11:25 PM   in response to: bill4 in response to: bill4
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what is the difference between a B4 and B5
How do I know which one I have
FKH161

Posts: 7,661
Registered: 12/29/05
Re: Location of 3rd speed coolant fan control switch thermal switch?
Posted: Nov 15, 2011 12:09 AM   in response to: bill4 in response to: bill4
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