Fan relay or aux fan switch bad? w124
 

My high speed fan runs on high all the time. When I unplug the relay, it shuts off. With the relay in, and I unplug the fan switch from the manifold, it still runs? Does this make sense? Is this a bad relay or some sort of short from the switch? Why would the fan still run even after I unplug the fan switch from the manifold. 1990 300E

Fan is also activated by
 

a coolant temp switch. If I'm not mistaken, somewhere near the thermostat with wire(s) plugged into it. Test it cold with a volt/ohm meter.

that was one of the switches that mercedes wired so that if the switch went faulty the fans came on all the time.i think it was considered less of an inconvenience than to have the engine overheat.anytime you unplug the switch it will run the fans all the time.sounds as though relay is operating correctly.perhaps the switch[blue i think] has an open circuit and needs replacing.

Fan Switch Question
 

I'm bumping this thread cause I have relevant Troubleshooting question

I have a 300TE. Fan froze up.

Replaced Fan, wouldn't run.

Put 12v on FAN, Fan worked.

Hooked Fan back up don't work.

Pulled wires off the Temp switch on the head and fan switched on.

Does this mean that switch is bad?

I had the car out and it got hot enough the head switch should have switched it on. I checked this by letting the car get well warmed up, took it to get gas where I know the head temps will rise while it's sitting. Started it up, temp showed pretty warm, fan no run.

The AC running does not switch it on.

Aux Fans
 

Start by doing "Advanced Searches" under Arthur Dalton's name.

Lots of them.

PeachParts Mercedes ShopForum - Search Results


PeachParts Mercedes ShopForum - Search Results

AND

'Just reading these will burn through a day:

http://www.peachparts.com/shopforum/search.php?searchid=6148720

Thanx!

Hi,
Can you provide the search terms you used for these 3 searches?

I didn't get to them all. Searches are volatile, so the links are no longer good.

Thanx!