Benz Forum banner

1 - 6 of 6 Posts

·
Registered
Joined
·
4 Posts
Discussion Starter #1
helo guys,

Car went ok till one day, while i was driving in rough city conditions, with the A/C on, i was surprised to se the water temp gauge pointing 120 degrees (very close to red line).
I changed the thermostate, no change.
i also checked the fan coupling, it seems to be working ok, as the rpm of the fan increases with the rpm of the engine.
however, the electric fans do not start with the a/c of, until the temp reaches 120.
what do you think? should i change the fan coupling? or maybe the electric fan sensor is damaged?
Thx
 

·
Registered
Joined
·
678 Posts
Right in front of the electric cans you'll see a thermo resistor. There are two different types. The older style looks like a black cylinder about 4-5 inches long. I have seen these go bad causing that problem. The newer style is a bracket with two plates. And behind those plates are two resistor coils. If I remember correctly, your electric fans are supposed to come on at about 90* C at a low speed, and increase in speed as temperatures raise. If you have the older style resistor, you'll need to do some wire splicing and a few minor modifications to install the newer style properly. I wouldn't doubt that the wire insulation for that resistor is probabally all deteriorated as well and should be repaired. This sounds to me like it's probably your problem, but I wouldn't know for sure unless I was there.
 

·
Registered
Joined
·
4 Posts
Discussion Starter #3
I understand. I'll do a check tomorrow. I'm not shure which type of resistor i have. However, with the a/c on, the electric fans come up shortly and they shut down and they come back and they shut down. Probably it's this resistor you say, that prevents them from operating normally.
I also checked for fluid leak and i haven't found any.
I hope changing the resistor will solve this .
Thank you.
 

·
Registered
Joined
·
4 Posts
Discussion Starter #4
I checked today, and indeed, the resistor (old style) seemed to be the problem. I checked the wires, and the insulation between them was melted. I didn't change the resistor yet, but i separated the wires and remade the insulation. Now, with the a/c on, the fans start at 90* C, and remain on for 20 seconds. I couldn't check if they start without the a/c, because outside it's pretty cold, and the main fan seems to handle the heat properly.
However i consider changing the resistor.
Thanks for your help. It saved me the money for going after a new water pump or fan coupling. :D
 

·
Registered
Joined
·
4 Posts
Discussion Starter #5
Re again.

The problem hasn't gone yet!!!! I just changed the main fan coupling and no change. The water tmp, without a/c on, still goes to 105-110 *C, when outside temp is just 22 *C.
However, the electric fan won't start with the a/c off no matter what, even though, i doubt that the fans are causing the overheating.
I also removed the old resistor, and i bypassed it, connecting the two wires directly, so that the fan may start at any time needed. It works only with the a/c on - the fans start at every 30 seconds, for about 10 seconds.
So what't next? I changed so far the thermostate, and the main fan coupling. Next, water pump, radiator , or what?
This thing is killing me, especially because it started so sudden. :(
 

·
Registered
Joined
·
48 Posts
your problem should be address accordingly or else you will end up spending $'s which should not be the proper thing to do.

The fan with or without the aircon on should be working the very moment engine temp reaches above 90 degree for a 140 a normal working temperature should be around 90 to 105 degrees.

Check the aux fan regulator first, then proceed to checking if the water is properly circulating thru the radiator and to the reserve tank, also check the motor oil and see if the level is right.

do this proceedures first before trying to replace all the parts which may be a waste of money time and effort.
 
1 - 6 of 6 Posts
Top