91 300TE M103 Aux Fans - Help needed? - PeachParts Mercedes-Benz Forum

d4mmo · #1 08-03-2012, 06:55 PM

Hi All,

Got an Aux fan problem

During normal driving temp ranges from 83- 95 - all ok I presume?

When in traffic or stopped - temp rises and rises
I know there are others that have experienced this, I think I've read all the posts.

Tonights experiment - 30 mile drive, all good; left running when I got home and temp rose to 110 before I bottled it......

....Increase the revs (viscous fans are engaged at this point) and suddenly the aux fans cut in - temp comes down to 80 (and don't stop)

Stop car let it cool for a while

Go back, turn ignition on - engine off (temp gauge about 65-70) - aux fans start on high, cuts off, then comes on immediately and stay on - 3 mins later they are still on, so switched ignition off.

Left car for a couple of hours - ignition on - nothing, no fans, everything cold

However, ignition on; unplug blue thermistor - nothing (I thought the fans would engage at this point)

Last weekend:
I jumped the pre-resistor (ceramic thing) and both speeds engage.
I also jumped the blue plug which engages the high speed fan

Couple of other things - there is no A/c gas in her, haven't managed to track it down in the UK locally, and don't fancy a R134 conversion. Therefore I presume that I won't get any low speed fan action, which I'm hoping won't be detrimental.

Also the fan relays don't have blade fuses in them - look like normal relays (I'll get a picture tomorrow)

Was going to check the resistance of the thermistor in the morning but doesn't make sense to me....

Why would the fans engage on a cooling engine?

What triggers the relay to get power in the first place?

The intermittent triggering of the fans, plus them engaging on a hot engine (once reved) feels like dry/dirty joints......but where???

Any assistance would be greatly appreciated - pulling my hair out here

Damo

mbdoc · #2 08-06-2012, 08:28 AM

Since the a/c doesn't work, the only fan operation is done by the HIGH speed fan relay.
That relay should be engaged at approx 107C.

Sounds like the radiator is partially blocked OR the clutch fan is weak.

ps2cho · #3 08-06-2012, 11:13 AM

You should not be overheating in your climate...not even close.

Either coolant low, radiator blocked or water pump is worn and providing very little cooling at idle.

You don't even need the aux fans, your system can handle it perfectly fine without it in that climate. Focus on radiator and water pump.

S124300 · #4 08-06-2012, 11:35 AM

Our 300TE overheats in the UK traffic, for no obvious reason, but runs normally on the move. Our previous one wasn't as bad but did get hot and lumpy idling in the summer traffic. Ambient temperature about 80 degrees downtown in the City.
It has improved some with a new fan clutch.
The electric fans will be switched by the a/c system using a pressure switch.

lee polowczuk · #5 08-06-2012, 12:45 PM

see posts under Arthur Dalton.... he has a resistor fix for it.... a couple of bucks...would make the fans come on at 100 degrees or so

Zulfiqar · #6 08-06-2012, 01:11 PM

With no A/C I dont believe that you can ever get the system hot enough to engage the high speed aux fans - unless your cooling system is faulty.

With A/C off in my E300D - I can try to beat on it - idle for ages (so much so that a clean shave turns to a beard) - run the snot out of it etc. it will absolutely refuse to heat up beyond 90*C on the gauge. (85 degree Tstat in engine).

With A/C it will stick to 95 or even say hello to the 100 line often.

BUT - I also have a strange issue, my high spd cooling fans will kick on when I switch on the key on a cold engine. It only happens in summer (and only happens in the engine is below 75). The relay will click about 10 times when it switches off.

I need to do some basic rig up testing to get some data.

dmplatt · #7 08-14-2012, 11:03 PM

Quote:

Originally Posted by ps2cho

Either coolant low, radiator blocked or water pump is worn and providing very little cooling at idle.

Either that or you have air in your cooling system... This happened to me, just warm the car up with the expansion cap off until the thermostat opens and add coolant/distilled water-some say it helps to squeeze the upper hose (preferably with gloves) to ensure complete air removal. Despite the 90 degree days-with the A/C on and stopped the temp never has risen over 95ºC. Sometimes the best fixes are the free ones!