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  #1  
Old 12-12-2002, 03:39 AM
azhari
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Unhappy M.B.Doc/Benzmac/Anybody Help! Tach/Electromagnetic Fan Problem

Alright guys. Check this one out.

Was looking under the hood one day with the engine running when I smelled burnt rubber.

Turns out, the wires going to the 2 prong temp sensor on the engine (the one nearest to the front) were burnt. I stripped back the wires all the way back (to the side of the wheel arch) until there were no signs of burning and renewed the wires going back to the sensor. The connectors looked ok so they were re-used.

I have swapped out the sensor, but even before re-connecting the 2 wires, fuse #10 blows (as soon as the ignition switch is turned to position 1). When the engine runs, the tach is out (of course, coz they share the same fuse).

Re-connecting the wires to the sensor does not seem to produce any burning or changes to the situation, but i disconnected them anyway.

The wires from the sensor seem to go back all the way to the back of the battery. Where do they end up? If I knew, I could do a short circuit test on the cable. Also, any switch or device at the other end could be causing the short in the first place.

What about the magnetic clutch, do these foil easily?

For your information, I have swapped out the multiple contact relay (20/30A behind fuses), OVP (to solve stalling problem) as well as the fuel pump relay (stalling). All fuses have also been renewed save #10 which keeps blowing.

Anyway, we're talking about a 1991 190e 1.8 RHD so I hope u guys r able to help me out on this one.

Thanks.

Azhari
1991 190e 1.8
Singapore
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  #2  
Old 12-12-2002, 10:13 PM
azhari
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Help

Help!!!

Azhari
1991 190e 1.8
Singapore
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  #3  
Old 12-13-2002, 01:01 PM
azhari
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Help???
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  #4  
Old 12-15-2002, 10:22 AM
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azhari,

the cooling fan switch you refer to usually fail-mine failed at 100,000miles plus and i changed it and the car no longer runs hot in traafic.

the electromagnetic clutch can fail-if you have a haynes manual for your car,then i suggest you look at it for more info on the fan clutch-there are a couple of electrical contacts below the cooling fan-have you checked the wiring that leads to the fan clutch?
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  #5  
Old 12-15-2002, 11:45 AM
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Wires usually burn solidly from the point of short to the point the wire changes size. The exception to this is where high current circuits have bad connections. In the case of a bad connection the connection itself increases the current and causes localized heating. Most temp sensors are low current sensing devices and can't draw any current due to the internal circuitry of the control unit monitoring them.

In the case of temp switches they are current carriers and the way you describe yours, I believe that the connections themselves were the problem. Check the circuit with an ammeter and verify that consumption is less than recommended fuse rating. If in doubt install an inline fuse of smaller rating in a strategic location.
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  #6  
Old 12-15-2002, 09:47 PM
azhari
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Hey Guys

Tks for your replies.

Sunil - I have the Haynes manual and use it for the more straightforward fixes. I have been a diehard Haynes fan since I bought my first manual for my 1979 Alfa Romeo Sprint 6 years ago. You have the 1.8, would my babybenz be similar to yours? Mine's a RHD.

Steve - you're right about "the switches being current carriers...".

There is only one sensor/switch for the electromagnetic fan, isn't it (the one on the valve cover - 2 prong on my 1.8)?

Could you guys advise on the path in which the cable travels from the temp sensor on the valve cover?

Is it connected directly to the electromagnetic clutch, or does it go thru' a relay?

The cable seems to go back from the side of the car towards the battery and disappears thereafter...where does it go to?

Tks again for your responses. Hope to hear from you guys again.
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  #7  
Old 12-16-2002, 03:30 PM
sunil190e-1.8's Avatar
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azhari,

mine is indeed a rhd car

the cooling fan switch on my car has 3 prongs but two wire connectors,is this the same as yours? cost me about 10 british pounds to buy and replaced it myself.

sunil
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  #8  
Old 12-16-2002, 07:46 PM
azhari
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Sensor

Sensor for the electromag clutch is the one on the valve cover, nearest to the front of the car, right?

Mine's 2 prong, and I swapped it out as soon as i discovered the burning wires. It cost me $15 Singapore Dollars and it's original Merc.

I'm trying to figure out whether I can isolate the clutch fan to see if fuse #10 still blows.

If I could only find those dang terminals...

Boy, is this gonnabe fun.

Btw, parts and service for the 201s and 124s are really cheap here because they are really common on our roads.

Tks
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  #9  
Old 12-17-2002, 02:03 AM
azhari
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You guyz know where the wires from the sensor lead to behind the battery?

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  #10  
Old 12-17-2002, 10:45 PM
azhari
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Or should I disconnect the wires to the electromagnetic clutch to see if it is shorting out the circuit?
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  #11  
Old 12-22-2002, 11:01 PM
azhari
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OK.

I just had an idea. Could the electromagnetic fan of my car be wired to be permanently on (maybe by previous owner)? This just came to my mind after I viewed a 190e 1.8 for sale on behalf of my kid brother.

The temp sensor (3 pin with 2 pins for connectors) was seen without the connectors. And the car was running without overheating.

Same goes for mine. I drive the car all day with the air-con on and at 32 to 34 deg C outside and the max running temp is around 89 deg C in stop-go traffic. It doesn't overheat.

And mine has been running with the 2 wires disconnected since the burning incident.

I am planning a long drive up to Malaysia soon and this issus gives me no peace of mind...

Another thing, after driving around town for about 45 minutes the other day, i switched off the car and spun the clutch fan. It moved only about 1/4 turn...?????????

Wouldn't that mean the clutch fan was working?

Yikes. This is freakin' me out.....

But it would be fun to solve this...as with the other problems...as it is, I have no tach till this day and that's no fun!!!



Any ideas?
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  #12  
Old 12-23-2002, 04:42 PM
sunil190e-1.8's Avatar
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after 45 minutes of driving,the fan should spin freely with the engine swtched off,that is if you have an electro-magnetic fan clutch .

on a viscous /fluid operated fan clutch ,you would expect a 1/4 turn after 45 minutes of driving.

freewheeling, if engine was cold

i get the feeling that your electromagnetic fan clutch is either faulty or been modified to stay on permanently in the hot weather conditions in singapore.

i know for a fact that in kenya,africa where we had equatorial hot climate,some people would throw out the thermostats and modify fan clutches to come on all the time-not a good idea as you lose engine performance/fuel economy and cause premature engine wear.
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  #13  
Old 12-23-2002, 11:03 PM
azhari
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Yep. I have the electromagnetic clutch. The 1/4 turn thing was psycological i guess (after having read to many posts in this forum).

I tried spinning the fan again this morning after driving and it does spin. Guess i didn't spin it hard enuff the other day.

Well, it may seem that my fan has been wired for good. That has gotta be solved.

Is there a way to see it in action?

Perhaps if i get someone to rev whilst I look at the fan? It should spin with the engine if it is engaged permanently, right?

Waddaya think?



My head is spinning right now...
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  #14  
Old 12-24-2002, 04:17 AM
sunil190e-1.8's Avatar
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azhari,

yes you could ask a friend to rev up the engine to see if the fan is the " on all the time mode".

on my car,there is like a 2mm gap between the magnet and fan assembly-you should be able to tell from this whether the gap is present =fan in freewheel mode or no gap=fan all the time mode. or note.

hope this helps
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  #15  
Old 12-27-2002, 11:54 AM
azhari
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Interesting...

I'll check it out.

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