W124 woes... - PeachParts Mercedes-Benz Forum

ZorroAMG · #1 05-23-2003, 10:22 PM

Help please! My car (1990 300E 12V) has been having overheating issues and I think the culprit is a sticking aux fan...that problem has been temporarily solved by blasting the heat a bit to bring temp down.. but today, as I was at the lights waiting to turn left, heat on, I noticed that the signal lights weren't ticking, then my abs light came on a bit and radio shut off....as soon as I turned the heat off, everything was fine....does anyone know what the prob is???

placo1 · #2 05-23-2003, 10:39 PM

I'm not an expert and hopefully others will chime in but when you start seeing that many items with problems I would look at the wiring harness first.

ZorroAMG · #3 05-23-2003, 10:55 PM

Thanks for the quick response...the symptoms seemed like a loss of power possibly caused by the HVAC system...I put in a new altenator in November, sp i don't think that's it..

#4 05-23-2003, 11:22 PM

I'm sure you'll find far better advice from 'the pros.' But to me it sounds like a bad overvoltage relay. I am addicted to this site like it's a crackpipe and although I'm not a professional mechanic, I recall several other posts where people have had weird electrical things happen like you described. The culprit in almost every case has been a bad overvoltage relay. This may also explain why your aux fans haven't been kicking on.

Good Luck. And wish me good luck on my new purchase! A '97 E420!!

ZorroAMG · #5 05-24-2003, 12:05 AM

EMB thanks...will check it asap...keep the thoughts coming guys...i appreciate it all

ILUVMILS · #6 05-24-2003, 09:41 AM

Hey Zorro, you've got a low voltage problem. Forget the OVP. ABS light coming on? Radio shuts off? Turn signals INOP? Low voltage. As soon as you switched off the ACC( which can draw quite a bit of current )the voltage rises enough to allow everything to start working properly. The OVP has nothing to do with the radio or turn signals. Regardless of how old/new the alternator is, make sure it's working properly. Also make sure the battery is o.k. Let us know how it goes.

kfuller · #7 05-24-2003, 10:24 AM

I have the same model and year. Had 2 or three things go wrong with the cooling system over a period of a month or two:

1) stress failure (I think) of aux fan fuse -- replaced fuse and hasn't reoccured
2) failure of temp sensor for aux fan prevented aux fan from coming on when it should -- replaced sensor
3) catastrophic failure of plastic neck of radiator -- replaced radiator and filled with the orange stuff

Been perfect ever since and runs much cooler now with the new radiator.

Had weird stuff happening with electrical system at some other time. Affected turn signals, radio, and gauges. Traced it down to two corroded ground points on the car chassis in the engine compartment. Cleaned and retighted and all cleared up. Read a tech note somewhere that said the connection should be spray painted to prevent future reoccurence. Next time I have a problem I'll do that.

Good luck with yours. I advise replacing the radiator before it goes. Cheap insurance.

Ken

PaulG · #8 05-27-2003, 11:58 AM

Definately sounds like low voltage..........

Check that with all the heavy-current stuff on ( HRW, A/C, headlights, heater blower etc, etc) there is still more than 12Volts at tickover.

If you haven't got a meter, treat yourself to one, it's the cheapest/most useful tool this side of a spanner.........

When turning at anything above tickover you should have a good 13-14V. Any less, the voltage regulator needs looking at.

It may not have been changed with the Alternator, depending on the design, it may be remotely mounted.

csnow · #9 05-27-2003, 03:49 PM

I vote for the voltage regulator like Paul said.

See if it can manage 12.5+ volts at the battery @ 2000rpm with Heater Fan on High, Rear defog on, headlights on High Beam.

#10 05-27-2003, 08:20 PM

I'm with ILUVMILS. My car had the fan turn on even though the 'off' button was selected and other weird stuff because of low voltage.

G-Benz · #11 05-28-2003, 02:14 PM

I "third" or "fourth" that!

Your model may be early enough that your alternator is equipped with the internal regulator as a seperate unit. Otherwise you are looking at another swap...

...was your replacement alternator a rebuild? Perhaps something wasn't installed properly when reassembled...

EricSilver · #12 05-28-2003, 02:48 PM

I vote for low voltage -- caused by radiator neck failure (cracking).

Coolant could be spraying onto the belt, causing some slippage over the alernator pulley (thus low voltage) and water pump pulley (contributing to elevated temperatures because of less efficient cooling.) If the radiator neck (or other part) is cracked, you will additionally suffer low system pressure, further reducing cooling capacity.

Squeeze the top hose when the engine is hot; it should be basically non-compressible. If you can sqeeze it significantly, and if you hear hissing, your neck likely has a hairline crack.

csnow · #13 05-28-2003, 05:43 PM

You are joking, right? Sounds like a comical sequence of crazy events. Sort of like something devised by Wile E. Coyote.

engatwork · #14 05-28-2003, 06:03 PM

When I had an E320 the car did some really strange stuff electrical stuff when the alternator was on it's way out.

ZorroAMG · #15 05-28-2003, 06:06 PM

Ok, to update the situation,

I took my car to where I had the rebuilt alternator installed, they ran a check and the alternator is fine, but only running at 51A out of the full 80A, thus, not charging the battery enough. He said the main belt's tension is too loose and that would cause slippage, the slippage would cause alternator to run at partial amperage, and that the slippage can also cause overheating since it runs the water pump as well...what do you all think? visual inspection of the belt appears chewed on one side slightly. Is it a major cost/job to replace the main belt?

Please Advise, thank you in advance, I really appreciate everyone trying to help

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