'91 190E Fan Clutch Wiring Diagram Wanted

[MB_mark]

Hi All,
I wonder if anyone has a wiring diagram for the fan clutch circuit on a 1991 W201 190E 2.0 (M102.962 engine and no aircon)- according to the Haynes manual & MB workshop discs the magnetic fan clutch is wired with a permanent 12v supply, and the earth is switched by the 100 degree temperature switch, and other diagrams I've seen it's vice versa.

Mine is permanently engaged, but is earthed at the inlet manifold, and I'm wondering if it's switched on the +ve side, especially as it's using a three pin temp switch.

Any help would be greatly appreciated as this is doing my head in now

Mark.

 

[grober]

I think they ran out of 2 pin switches a while back so everyone getting a replacement gets a 3pin whether they have aircon or not. As far as I know the switch still functions by switching the electromagnetic clutch as the coolant temperature rises. the other pin switches the auxilliary fan relay which in turn turns on the electrical fan/s for the air con in front of the radiator. Think of the switch as exactly that. It either switches on a 12v supply to the clutch which is earthed elsewhere. OR the magnetic clutch has a permanent 12v supply which is earthed by the switch. You will have to do a little testing to find out which. Either way it looks as if the switch needs replacing unless you have some short to earth in the wiring to the electromagnetic clutch.

 

[Dec]

A usefull link for you... http://www.autolib.diakom.ru/CAR/Mercedes-Benz/1991/190E/SYSTEM%20WIRING%20DIAGRAMS/

Dec

 

[MB_mark]

Hi,
Thanks for the replies guys. Just had a look at the temperature switch and the third wire is actually for the temperature gauge, so it looks like MB have combined the fan switch & temp gauge sender.

Thanks for the link to the Russian site, I'd already looked at that and it's one that suggests mine is wired as contant earth, with a switched positive.

I've tested the switch with my multimeter and it seems the switch is fine, closing at around 100 degrees, so it would seem like it's either a short on the wiring or a sticking relay if there is one there....if there is I can't see it!

I'll keep looking!

Thanks again,
Mark.

 

[MB_mark]

Sorted!

Hi Guys,
Thanks for eveyone's help...all sorted now...

The postive wire comes directly from fuse No.10 in the fusebox, through the temp switch and the wire out of the switch goes to the fan clutch magnetic solenenoid, which is permanently earthed - no relays or anything like that, as there's no auxilary fan on UK models without a/c, and the third wire on the switch is for the temperature gauge.

I've trawled wiring diagrams, scoured this and other forums etc looking for answers, but nothing was making sense. In anycase I pulled the black insulation sleeve off the wiring to the temp switch and some bodgeing muppet has stripped the insulation off the wires inside, and wound them together, then put them back in the sleeve so it looks like it's not been touched!!

In anycase repaired the wiring and everything's happening as it should, except the switch is a bit hit and miss, which I suspect that's why its been done, and which I'll replace this week!

I would really like to get my hands on the bodger who did this as he's wasted hours of my time, all for the sake of a £20 switch

In anycase, hope this helps someone else, at least something good will come of it!

Mark