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  #1  
Old 06-01-2002, 03:47 AM
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Angry Strange Electrical Gremlins! Help!!!

The strangest thing started happenning with my 1994 E420 this afternoon and evening. I was driving along, and all of a sudden, three problems occurred simultaneously. First, I noticed that the ABS light was on. Second, my A/C shut off, and immediately started blowing hot air. Third, even though my aftermarket radio was still getting power, apparently the factory amplifier (located in the trunk) stopped working, because there was no sound. A couple of minutes later, every thing returned to normal.

Hours later, I was driving around in the evening, and the same symptoms occurred again, and this time, I noticed that the dash display was significantly brighter than normal, and my headlights seemed much brighter as well. Again, after driving around for a while, everything returned to normal, and the dash lights and head lights returned to their normal brightness levels. Obviously, the way all of the symptoms occur and disappear simultaneously, there must be some connection, but I haven't the foggiest idea what to look at first. Any helpful responses are greatly appreciated.
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  #2  
Old 06-01-2002, 04:23 AM
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This sounds like some things are losing electrical power at the same time as other are getting too much. I would start by checking all the wiring and connections between the alternator and battery, including earth (ground) connections. Am I right in thinking the battery is in the boot (trunk)? Any dampness here could lead to corrosion around the terminals.

Either way you need to get this sorted quickly, excess voltage can destroy electronic components including those in the alternator itself.
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  #3  
Old 06-01-2002, 09:43 AM
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I had essentially the same problems when my alternator went out on the E320 at around 100k. It only did it in stop and go traffic. There was absolutely no problems out on the highway where, I guess, the alternator was able to keep up.
How many miles are you showing and does it do it on the highway versus stop and go traffic?
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  #4  
Old 06-01-2002, 11:08 AM
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I will second Jim's suggestion, on the alternator. Without a diagram its harder to draw conclusions, but from the brightness of your lights it could be that the controllers shut down to protect themselves from too much voltage; check that regulator.
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  #5  
Old 06-01-2002, 11:14 AM
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Thanks for the suggestions. My car has 138,000 miles on the clock. It looks like I'll be paying a visit to my mechanic, and I'll arm him with your responses. Is there any connection or component in particular which would cause the ABS light, stereo amplifier, and AC to fail, coupled with the instrument lights and headlights to get brighter?
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  #6  
Old 06-01-2002, 11:22 AM
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Still sounds like an alternator issue, especially if it is the original.
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  #7  
Old 06-01-2002, 01:01 PM
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I have a 94 E420 with 115,000 miles and I have experienced 2 crazy events like yours but they were related to the fuses. With age, the fuses have all become quite brittle, and I had one situation recently where the ABS light came on while driving, and speedometer went out etc., but car continued to operate. I also had one fuse that caused the radio to stop working, so when you turned the radio on it would turn on the dome light and seatbelt light....strange things like that. Not sure if that is your problem, but take a look. The fuses looked OK; did not show as blown, but were turning off and on.
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  #8  
Old 06-01-2002, 02:04 PM
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I replaced all of the fuses about six months ago, so I doubt that the fuses are the problem, but I'll check just in case. I'll have my mechanic check it out on Monday, with an eye towards the alternator. Thanks for all the help, and I'll follow up when the repairs are done.
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  #9  
Old 06-01-2002, 03:41 PM
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Over voltage protection relay blows a fuse if the voltage gets too high and this is how power is shut off to some devices. It cannot be restored without operator intervention, i.e. replacing the fuse. However if the connection between the alternator and battery is lost there is no way the alternator can control its output voltage which may be why lights glow brighter. I am guessing that the ABS etc is still being fed from the battery side of the fault and shutting itself down in response to reduced voltage at that point.
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  #10  
Old 06-01-2002, 05:00 PM
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I'm pretty sure that the 4.2 V8 doesn't have the OVP.
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  #11  
Old 06-06-2002, 12:25 AM
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Well, $500 and a remanufactured alternator later, and the car is running again. However, I noticed two strange after effects. First, the power antenna no longer works. I have already checked the fuse which controls the antenna, and it appears fine. Second, I seem to have lost the highest fan setting on my HVAC. The low and medium speed still work normally.

I know for certain that both of these items worked before my alternator went out. My mechanic checked the alternator, and it was apparently putting out 17 to 18 volts, or way more than normal. Is it possible that I fried the antenna motor even though the fuse did not blow? The reason I believe that the fuse is still good is due to the fact that the same fuse controls a great deal of other equipment, such as the power door locks, and everything is still good there. As for the HVAC fan, I heard that it is actually controlled by a resistor, but the usual failure mode is to lose every speed other than the highest speed.

As usual, any helpful responses are greatly appreciated. Thanks in advance to everyone who contributes to this great forum.
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  #12  
Old 06-06-2002, 02:17 AM
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Another addendum to my post. Went driving tonight, and it appears a couple of brake lights may be burned out now, as the dash sensor is lit up. Who would have thought that this problem would rear its ugly head in such a manner!
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  #13  
Old 06-06-2002, 08:28 AM
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Lost my ACC fans yesterday on the way in to work and immediately began drawing heat with the temp. control wheel set to max. cool? My vehicle is a different model than yours.

In my case, fuse #5 affects the ACC blower. I pulled over and looked at it. Fuse did not appear to be blown. I replcaed it anyway. Wah-Lah...ACC blower fired up and the A/C was back.

You mentioned excess voltage. I wonder if perhaps the voltage regulator was/is the problem? Also went thru similar problem awhile back. ABS/SRS lights came on - cars idled poorly. Brushes in voltage regulator were worn. Replaced and that was the end of that.
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  #14  
Old 06-06-2002, 11:41 AM
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Like I mentioned, with the new alternator, the car is running well again, but I think that the over-voltage it was producing may have damaged a few other components, namely, the high speed fan setting, the antenna motor, and a few taillights. I don't suppose there is any single component which could affect all of these diverse components, right?
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  #15  
Old 06-06-2002, 11:45 AM
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You have a new alternator and many have built in voltage regulators. Many don't. I'm not familiar with your car. If your voltage regulator is not part of the alt., was it also changed?
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