190E Overheating Solution
 

I have a 1986 190E 16V--with 81,000 miles. Like many of you on this forum, I have had overheating problems in stop and go traffic. I finally found the solution--at least for my car.

I won't bore you all with why it took me so long to find the solution--I guess old age just makes you slow.

In my case it became apparent that the fans were not coming on at the correct temperatures. The main fan would come on at about 115 degrees C, the aux fan above that. I couldn't believe that the problem was the temp switches, so I checked everything else--and everything was functioning.

I ended up replacing the thermostat ($12) when I changed the coolant. I think it never fully closed or opened, so I wasn't getting full flow.

I then changed the temp switch for the main electromagnetic fan clutch (about $18) and the temp switch for the aux fan ($24).

Now the car does not overheat. The main fan comes on at 100C like it should. The aux fan comes on at 105C like it should. Car does not get above 100C in any traffic. I have yet to test it on a hot day with the A/C on, though, but I have confidence now.

I guess in a 16 year old car ANYTHING can be bad! You can easily check the other parts of the circuit for operation by removing the plug from each of the temp switches and shorting out the terminals. The appropriate fan should go on immediately. If it doesn't, then something else is wrong in your case.

Good luck to all you overheaters!

Tom Elerding

Way to go, Tom!

Gives us all a little more hope that we too will some day get our complicated cooling systems to work right again!

Steve

My heating problem disapeared when I started using higher Octane fuel. I used to drive around with "Regular" fuel (in days when I knew no better) and the temperature was noticeably higher - the fan used to come on very often. Now that I use "Super" fuel, the engine temperature seems to be lower/normal.

HAd a similar problem with my 190E when i first got it it turned out to be the switch for the electomagnetic fan. As i live in the chilly UK mine dosent have any aux fans, just the main one. Funny though, when the switch went my rev counter stopped working as well, turns out they are protected by the same fuse!!

Where's the switch?
 

I would be interested to know wher the electromag clutch fan switch is located. I know the sensor is on the valve cover (mine is the 2 prong type).

I am chasing a short in this circuit and have isolated the fan.

Now I have my tach back!!!

I am checking tomorrow if the clutch itself is faulty (unlikely) by applying voltage to it but since you mentioned a switch, I'd like to know where yours is located.

Thanks.

Azhari
Babybenz 1991 190e 1.8

Hi azhari. The switch is located at the topside on the front of the engine. The 2 prong sensor is the switch and I hope you are referring to the one next to the valve cover. Correct me if I'm wrong.

You test the switch by pulling off the connector halfway so it's still connected. The shorten the pins with a screwdriver and the fan should engage if everything else is in order. This is how the switch works...when tempeture rises it closes the circut.

this is kinda ghetto. i eliminated my AC system because it was kaput and would have required much cash to repair it. when i did that i just wired a switch from the fan through a fuse to a dash switch. now when i'm sitting in traffic on a hot day or when i leave my car parked and idling i just flip the switch and the engine stays cool. i did this because the auxillary fan will not turn on without the AC being on also. since the AC was gone i was getting no benefit from the aux fan.

The switch is Ok coz I've replaced it.

However, the wiring has been screwed up by a short which i've identified.

I have isolated the clutch from the rest of the car.

Now, testing the clutch directly with +12V and the engine running (and GND connected, of course) does not produce any reaction on the part of the clutch.It still freewheels when it's supposed to lock up, right?

The 2 tiny wires going to the clutch have kinda burnt thru' though.

I'm looking at renewing these wires (+12V & GND) IF they can be pulled out of the clutch. I can't see the point where the wires enter the clutch so I'm not sure if they can be taken out (via connector, perhaps).

Would you have any idea with regards to this issue?

Thanks for your help.

Azhari
Babybenz 1991 190e 1.8

you will find that the haynes manual has photos of the wires leading to the clutch fan-see picture 7.8a,page 3.8-cooling,heating and ventilation systems.-the leads are visible but only if fan is removed for clarity.;)

Yikes!

Must have missed that one.

Thanks for pointing it out. I'll check the manual again.

Azhari
Babybenz 1991 190e 1.8

:D

Solved!!!
 

Sunil

Managed to pull clutch wire loom out and tested it. It's OK!!!

So where does that leave me, with a fried clutch!!!

Got a new clutch for 65 bucks, a new wire loom for 15 bucks (the old one was stiff from the heat), 30 bucks labour and i'm back in business!!!

Tech also tested existing clutch fan wiring for shorts and they're OK too!!! Apparently, the fried clutch was shorting out the circuit.

I love these cars...and this forum too!!!

Azhari
Babybenz 1991 190e 1.8

azhari,

good to hear about the happy ending to your problem.:D