Auxiliary Fan - PeachParts Mercedes-Benz Forum

Adriel · #1 06-15-2013, 01:55 AM

Auxiliary fan isn't coming on, so ram and I have been trying to put our heads together.

What we know:
Auxiliary fan works when battery voltage applied directly.
Auxiliary fan controlled by two temperature switches, one on the block and one on the receiver/dryer. Both passed and/or are new.
Auxiliary fan affected by low refrigerant pressure.
There sounds like the refrigerant system has a leak from the expansion valve, as when the compressor comes on, there is a microsecond hiss from under the right had side of the dash.
Receiver/dryer temperature switch bypassed doesn't cause the fan to come on.
Auxiliary fan relay is new.
P3/ Relay ground (30) has no ground (one on volt meter with no reading).
6P6/ 87 has ground.
87a has 0.1 volts.

Now what?

Thank you in advance!

Mölyapina · #2 06-15-2013, 06:30 AM

Quote:

Originally Posted by Adriel

Auxiliary fan isn't coming on, so ram and I have been trying to put our heads together.

What we know:
Auxiliary fan works when battery voltage applied directly.
Auxiliary fan controlled by two temperature switches, one on the block and one on the receiver/dryer. Both passed and/or are new.
Auxiliary fan affected by low refrigerant pressure.
There sounds like the refrigerant system has a leak from the expansion valve, as when the compressor comes on, there is a microsecond hiss from under the right had side of the dash.
Receiver/dryer temperature switch bypassed doesn't cause the fan to come on.
Auxiliary fan relay is new.
P3/ Relay ground (30) has no ground (one on volt meter with no reading).
6P6/ 87 has ground.
87a has 0.1 volts.

Now what?

Thank you in advance!

Can you just run voltage directly to the fan to see if it turns? I was sure the starter on a neighbor's lawn mower was dead until I ran power directly to it -- it ran!

<-- It was quite loud, too...

Bio300TDTdriver · #3 06-15-2013, 06:49 AM

Quote:

Originally Posted by Jooseppi Luna

Can you just run voltage directly to the fan to see if it turns? I was sure the starter on a neighbor's lawn mower was dead until I ran power directly to it -- it ran!

<-- It was quite loud, too...

"What we know:
Auxiliary fan works when battery voltage applied directly."

Mölyapina · #4 06-15-2013, 07:59 AM

Quote:

Originally Posted by Bio300TDTdriver

"What we know:
Auxiliary fan works when battery voltage applied directly."

Adriel · #5 06-15-2013, 11:29 AM

I am one that likes things to be right, and will correct others if need be. I now know how annoying the latter is, so stopping. Point is, I could just make it run all the time, but that isn't right. Therefore, like to figure out what is wrong and correct it.

Tram had me check the fittings under the dash and could only access three out of four with the blower motor in. One did click tighter so will see if that did anything. Said start with the possible leak first, then get the correct amount of refrigerant.

my123ca · #6 06-15-2013, 11:40 AM

Did you check the fuse yet? Check the line from the fuse to the relay too.

Adriel · #7 06-15-2013, 11:45 AM

Quote:

Originally Posted by my123ca

Did you check the fuse yet? Check the line from the fuse to the relay too.

Thank you so very much!

Fuse was good last time I checked. Hard to trace the wires, but don't see anything obvious.

my123ca · #8 06-15-2013, 12:16 PM

Its the fuse on the upper right and #14 on my car. The fuse holder on mine had melted away. Check voltage to #3 position of ice cube holder. You should have 12v there. Your aux fan should be working if you bypassed the temp switch in the drier.

Adriel · #9 06-15-2013, 12:18 PM

Quote:

Originally Posted by my123ca

Its the fuse on the upper right and #14 on my car. The fuse holder on mine had melted away. Check voltage to #3 position of ice cube holder. You should have 12v there. Your aux fan should be working if you bypassed the temp switch in the drier.

Thank you so very much!

As I said, there is no voltage there. Sorry that wasn't clear...

So, pin 3 is power, then where do the others go, or what do they do?

my123ca · #10 06-15-2013, 12:41 PM

Hope this helps.

Adriel · #11 06-15-2013, 12:50 PM

Quote:

Originally Posted by my123ca

Hope this helps.

That is exactly what I was looking for! Thank you so very much!

ROLLGUY · #12 06-15-2013, 08:08 PM

Quote:

Originally Posted by Adriel

That is exactly what I was looking for! Thank you so very much!

I like to wire in a relay so that the coil is hooked up to the compressor clutch wires, and the fan is switched by the relay with direct fused power. It runs only when the compressor is running. I don't like to rely on the thermal fan switch, new or not.

Adriel · #13 06-15-2013, 08:35 PM

Should sparks be coming from my compressor?

Very pretty, but...

Quote:

Originally Posted by ROLLGUY

I like to wire in a relay so that the coil is hooked up to the compressor clutch wires, and the fan is switched by the relay with direct fused power. It runs only when the compressor is running. I don't like to rely on the thermal fan switch, new or not.

Thank you so very much!

I was thinking something like that, but at this time, don't have my wiring stuff as back in California... Happen to have pictures or a diagram?

Still have the summer sale for the compressors? Just planning...

ROLLGUY · #14 06-15-2013, 08:43 PM

Quote:

Originally Posted by Adriel

Still have the summer sale for the compressors? Just planning...

I sold one, and have had inquiries on two others. The 4 I have left may go faster than I had thought....Rich

ROLLGUY · #15 06-15-2013, 08:56 PM

Quote:

Originally Posted by Adriel

I was thinking something like that, but at this time, don't have my wiring stuff as back in California... Happen to have pictures or a diagram?

I don't have a diagram, but could probably draw one up. It is actually quite simple. You can use any relay, a 'Benz relay and socket from a parts car (under the plastic box on inner fender) will work, and even be mounted there (longer wires are needed). There are 2 ways. 1) Just parallel the two wires going to the compressor on to the coil connections of the relay, and the N/O relay contacts put +12v to the fan via a separate fused 12v source (attach the - to the body, only switch +). That is suggested for a 126, as they have fuse holder melting problems anyway. 2) A 123 just needs the aux fan switched by the relay instead of the thermal switch. The coil is powered the same, with the compressor power, and the N/O contacts connected to the thermal switch wires. Fuse overheating problems on a 123 aux fan circuit are not as common as the 126....Rich

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