The low speed on the aux fan is not working. If I unplug the blue connector from the thermostat they don't start either. I did change both relays in position B and C and the resistor behind the headlight. Now if I am touching the wires from the red sensor on the receiver dryer the fans are starting. There is another sensor on the dryer (black) that I did not touched. What it should be. Then if I will need to change any of those two sensors I will need a full recharge of the system? Thanks guys

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Radu Negru

Yes.

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

So witch one is "the one" The red or the Black?

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New Addition to the family
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Radu Negru

Which one what? I answered the question about whether you would have to discharge and recharge the AC to change either switch. The switch with pigtails runs the low speed fan. The switch with connection at the switch is the low/high pressure switch. It turns the AC compressor off if the pressure is too low or too high.

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

Thanks, thats what I need to know. So the pigtail ones control the low speed fan.

__________________
New Addition to the family
2013 Passat TDI 5Miles
2004 E500 4MATIC Wagon 95k
1996 E300 Diesel 173k Sold
1993 300E 2.8 230k Sold
1994 E320 White Wagon 373K Sold
Still dreaming about ....500E


Radu Negru

The pigtail is the correct one, but do not assume that the switch is bad..the most likely problem is your a/c system is low on refrigerant and not allowing the high side pressure to get to the cut-in spec pressure of the low fan switch.
Look in the eye-sight and see if you have lots of bubbles..or better yet, put some gauges on the system and see what the high side pressures are.
All as you have done with the jumper is verified the elctrical system for low fan, minus the switch..you have not yet diagnosed the No Low Fan problem.

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A Dalton

Would this model have the same resistor that my 420 has? If so, I would check out the wiring on this resistor. Mine has been "repaired" 4 times in the last 4 years - and I know that I am certainly not alone.

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It is a truism that almost any sect, cult, or religion will legislate its creed into law if it acquires the political power to do so. Robert A. Heinlein


09 Jetta TDI
1985 300D

He states new R15 droppinng resistor in his first post..and jumper at high side switch verifies resistor circuit OK...

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A Dalton

Hi Arthur,
Let me tel you what I did .
I hope that I did not run onto other problem.
I checked the receiver dryer and NO Bubbles. Than I got that walmart can and I filed up a bit more. The fan started and now it does not stop at all. Even if I stop the ac. The only think that make them stop is unplugging the pigtail.
What it could be now.
Please help

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New Addition to the family
2013 Passat TDI 5Miles
2004 E500 4MATIC Wagon 95k
1996 E300 Diesel 173k Sold
1993 300E 2.8 230k Sold
1994 E320 White Wagon 373K Sold
Still dreaming about ....500E


Radu Negru

Arthur - I read that, but apparently it went into my eyes, and out my _ _ _ .

Sorry 'bout that!

__________________
It is a truism that almost any sect, cult, or religion will legislate its creed into law if it acquires the political power to do so. Robert A. Heinlein


09 Jetta TDI
1985 300D

Larry.

It shows that you are thinking , cuz the Resistor is in the low fan circuit and is a common fault on such.....so you are excused.....

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A Dalton

<>

OK ..sounds like you may now have an overcharge..

See if the fan stops after a minute or two time when the a/c is shut off..it takes a little time for the high side to come back down when a/c is turned off.
Give the sw a few little taps ..you may in fact have a bad/sticking switch.
That is where gauges tell the tale..........



Post findings.

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A Dalton

You were very right. It may be a sticky switch.The fan stops after 3-4 minutes in Economy mode on the climate control. Maybe because I use one of those walmart cans with R134+sealant? Also the system is not cooling that good as before. What do you think?

__________________
New Addition to the family
2013 Passat TDI 5Miles
2004 E500 4MATIC Wagon 95k
1996 E300 Diesel 173k Sold
1993 300E 2.8 230k Sold
1994 E320 White Wagon 373K Sold
Still dreaming about ....500E


Radu Negru

< Also the system is not cooling that good as before. What do you think?
>

As I said, I think you may be overcharged.
Accurate low aux. fan pressure switch diagnosis requires high side gauge readings/measures.
And accurate system charge should be done by weight, although gauges and experience will work well.
One can use eyesight and fan activation to get it close , but if you have a bad switch, that technique is out and system pressure readings are the only [ and correct ] way to verify sw cut-in/cut-out specs....

__________________
A Dalton

I did replace the pigtail sensor and have the system completely evacuated and charged professionally but still does not work. The a/c cools perfect but the first speed on aux fans does not work.
So I have the following new parts in relays (30 amp and 15 amp) new resistor.
The mechanic told me that the only option is the push unit.
What Do you think?

__________________
New Addition to the family
2013 Passat TDI 5Miles
2004 E500 4MATIC Wagon 95k
1996 E300 Diesel 173k Sold
1993 300E 2.8 230k Sold
1994 E320 White Wagon 373K Sold
Still dreaming about ....500E


Radu Negru