Hi
1976 450SEL, euro.
My electric fan on the front of the A/C condenser is running all the time when ignition is on. Before i dive into the wiring diagram, are there any common faults which cause this?
Thanks
John
John I had the exact issue the past few weeks.
Took the car to an air conditioning guy.
He diagnosed the part I've circled in the picture. A switch of some kind, I don't know the name.
Changed it over for another from a donor car and all is good again.
Try that option 1st maybe.
Note.
I have the M110 6 cylinder, could be a different issue for an 8 possibly.
Quote from: mrkozzy on 07 November 2020, 10:44 AM
John I had the exact issue the past few weeks.
Took the car to an air conditioning guy.
He diagnosed the part I've circled in the picture. A switch of some kind, I don't know the name.
Changed it over for another from a donor car and all is good again.
Try that option 1st maybe.
Note.
I have the M110 6 cylinder, could be a different issue for an 8 possibly.
That would be the pressure switch, which turns on the AC fan if the pressure in the system increases.
Quote from: ptashek on 07 November 2020, 02:50 PM
Quote from: mrkozzy on 07 November 2020, 10:44 AM
John I had the exact issue the past few weeks.
Took the car to an air conditioning guy.
He diagnosed the part I've circled in the picture. A switch of some kind, I don't know the name.
Changed it over for another from a donor car and all is good again.
Try that option 1st maybe.
Note.
I have the M110 6 cylinder, could be a different issue for an 8 possibly.
That would be the pressure switch, which turns on the AC fan if the pressure in the system increases.
Thanks guys. I'll try that
John
The M110 6cyl also has a 100°C fan switch in the cylinder head near the temperature gauge sensor, as the name suggests when engine temps get over 100°C it turns the fan on. I assume the V8 has a similar sensor, you can unplug it to see if the fan stops.
By own experience I bet the problem is rather the 100 switch. Being a new acquisition maybe you have recently washed your engine. And washed the entire car too. This switch is connected to a relay covered behind the panel in your A Pillar. In my case water drips got into that area causing your same problem. But I would remove, check and dry up both switches in question. Those 3 usual suspects is a good way to start your Sunday.
Good luck
Quote from: revilla on 08 November 2020, 02:02 AM
By own experience I bet the problem is rather the 100 switch. Being a new acquisition maybe you have recently washed your engine. And washed the entire car too. This switch is connected to a relay covered behind the panel in your A Pillar. In my case water drips got into that area causing your same problem. But I would remove, check and dry up both switches in question. Those 3 usual suspects is a good way to start your Sunday.
Good luck
Very useful, thanks Robert and Nabstud
The engine bay hasn't been washed, but I will check those points anyway.
Which side A-pillar should I look for that relay?
Cheers, John
Hi John.
Mine is a LHD and they are located on the driver's side. Anyway, they are easily identifiable once the little panel is removed. You'll see a vertical rack/bracket holding 3-4 aluminum cube type relays, it's one of them. Remove one at a time until your fan stops. Then you can swap with another one from the same rack to test. They are all interchangeable with same pins configuration.
Cheers
Robert