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Old 02-03-2002, 01:29 AM
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Question Discharged

I have a 1988 300 CE. The car was working fine until I took it to Circuit City to have a Viper 550 ESP alarm sytem (with remote start and keyless entry) installed. It took the installer 3 days to figure it out (with the vacuum locks and more). On day 3, he finally gets it working and I drive away happy until I get home. A few hours later, the car doesn't start and the battery appears to have totally discharged (died). I had to keep jumping the car to start it, so I finally bought a brand new 12.8Volt Die Hard battery at Sears. Only after 4 hours the brand new battery dies - something is draining the battery.

What is the cause of this? Could it be the alternator not providing enough charge to the battery? I didn't think it could be because I disconnected the battery after getting the engine running and it still kept running. But I think I have narrowed it down to an improper car alarm installation. Go figure, it took Circuit City 3 days until I could pick up the car! Perhaps the wiring is totally off, a loose wire touching something, ???

I'm not sure where to go from here? I'm not trying to spend a fortune on a new alternator; I just spent almost $400 on a car alarm system that just seemed to cause a ripple effect. I'm worried also that the perhaps this "improper" car alarm installation may have caused permanent damage to my engine. What's a female to do now? HELP!!!

I'm going to Circuit City tomorrow to yell at them and find out what the heck is going on here. All I wanted was a simple car alarm system that worked (since my car just got broken into two weeks ago)....what luck I have, huh?

Help a little lady out in Virginia....
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Old 02-03-2002, 04:38 AM
Ashman's Avatar
Service Advisor
Join Date: Sep 2000
Location: Sherman Oaks, CA
Posts: 4,748
He probably miswired the alarm. And something is staying on, maybe the trunk light or something, though i would think it would not be draining the battery in such a short time.

My suggestion would be to organize to have it looked at by a shop that knows how to install alarms in a meredes.

All he had to do for the locking mechanism was tap into the trunk lock to get the door locks and trunk to lock with the alarm.

The only other item would be the sensors and ignition kill for the alarm. The remote start system could be leaving computers and such running at all times. you never know.

I have a friend who installs alarms all the time. Its really not that hard until you start adding all the extras, like windows opening and closing, door locks to some cars, and remote starting etc. Knowing which wires to tap into is the key, and testing wires is the key.

Lets just hope that he somehow did not massacre something in your car when learining how to install ina mercedes.

When I have alarms installed, I have it do the basics, arm, disarm, kill ignition, shock sensing, and door locks. I leave flashing parking lights off, and I leave chirping off. I prefer it to arm silently and not flash the parking lights.

An alarm should not take more than a few hours to install, not a few days. Obviously the guy is still learning or just has no clue how to wire a benz. I would talk to them and find out if he has installed alarms on a mercedes before. If he has not, I would suggest you try to get a refund and the alarm uninstalled and the car reverted back to how it was before they wired the alarm. If your problem still persists, then the alarm may not be it, but it sounds to me like this person just did not know how to wire a benz properly for an alarm. not that it should be much different than any other car, but it is different and can't be wired up just like any other car, it must be done carefully.

I would definately look into a shop that specializes in alarms and has worked on mercedes before. Perhaps this problem is new, but I would think that somethign is just not right with the alarm based on the fact it was not happening before.

'92 300CE - Sold
2004 C240 - C7 Wheels
2015 ML350 - P1, Pano, Ash poplar wood, Sport Dinamica interior, Running Boards Keyless go.

Last edited by Ashman; 02-03-2002 at 04:43 AM.
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Old 02-03-2002, 02:18 PM
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Angry Update on my car alarm situation....

Uggh...this is so frustrating! Anyways, this morning I went back to Sears to have them check the battery and the charging system. I thought maybe my alternator or voltage regulator or brushes went bad so I did this before going to the car alarm installers. Sears guys were unable to diagnose the problem and told me to "see my Mercedes Benz dealer". They said they were unable to run diagnostics because the serpentine belt was loose and they were unable to tighten it. They said their charging testers were unable to do a diagnosis if certain belts are loose.

But eventhough they say my Serpentine belt is loose, why does the battery discharge when the car is off. I didn't recognize any buzzing noises either. My guess is that it really is the car alarm installers fault. By the way, I had to jump the car to get it back to Sears this morning and luckily it put back enough juice for me to bring it back to Circuit City.

So just an hour ago I took my benz back to Circuit City and complained that this Viper Alarm system is draining my brand new battery. Believe me, they heard my anger and I told them to have it totally removed and brought back to its original state when I first took it in. I just hope they haven't caused permanent damage on my electrical system. I asked for a full refund and I hope they even pay for the new battery that I had to buy. I will have to wait and see what happens.

I'll keep everyone posted once I get the car back today or however long it takes them to disassemble the car alarm, keyless entry, and remote start. After I get it back, should I go to a reliable MB dealer to have them overlook the electrical system? Would a full diagnostic check on my car be expensive? I'm worried the installers are going to do another careless job on the uninstallation.

Thanks for everyone's input so far. I've actually learned a lot more about my car by reading all the postings. I wish I had checked this site before considering an aftermarket alarm system and going to Circuit City.

Do you recommend I go to MB dealership to have an alarm system installed? I would like it done right next time around. By the way, I did ask the installer if he had worked on Mercedes before and he said he had which gave me some confidence in his work, but obviously he wasn't as skilled as I had thought. He also mentioned that DEI (the maker of the Viper alarm) didn't have a schematic for my make/model (88 300 CE), so they were basically working on their own intuition I guess. Isn't there a way to download wiring schematics?

Anyways, I'll be back again to give updates.
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Old 02-03-2002, 03:36 PM
Registered User
Join Date: Jun 2000
Location: Plano, TX
Posts: 2,476
Can't fix your alarm system, but I do have one valuable piece of advice. Never, never, never ever disconnect the battery while the car is running. The battery acts as something of a filter for voltage spikes in the electrical system. On some cars disconnecting the battery can destroy enough electronics to render the car unusable and cost several thousand dollars to repair. Sounds like you're OK, but don't do it again. For that matter, it doesn't prove much of anything about the alternator/charging system either.
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Old 02-03-2002, 08:22 PM
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Update but no resolution

The car alarm installer thinks I have a bad alternator, he got a reading of 12.3 V while the car was running and said it should be around 14.0V. So he didn't uninstall the car alarm system. I'm picking up the car tomorrow and bringing it to my mechanic who said he will check the alternator and voltage regulator. Now I don't know who or what is the blame for my car not starting.

But this still doesn't make sense to me. What does a bad alternator have to do with a battery that is in park? It still seems that something is draining juice from the battery. So does the alternator or voltage regulator have any purpose while the car is off and in park? Does the alternator still hold a charge while in park and does it have to be more or less than what's in the battery?

Only four hours after I put in the new battery, the alarm LED light and the dashboard clock stop working meaning there's not enough juice to keep it going. I did drive the car for 15 min on the highway after I put in the new battery; therefore, if it is a bad alternator then that 15 minute drive might have been running all on battery then, right? Is it possible for a battery to discharge so much that a little LED light stops blinking?

Who, what seems to be the culprit here? A bad alternator or a bad car alarm installation or is it something else even?

Thanks in advance for any input!
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Old 02-03-2002, 10:18 PM
G-Benz's Avatar
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Join Date: Apr 2001
Location: Dallas/Fort-Worth
Posts: 5,711
A couple of years ago my wife had a Jaguar XJS with an aftermarket alarm (already installed when the car was purchased).

One day, the car wouldn't turn over...I thought the battery was due for a replacement, so I dropped a new one in. Everything was okay for about a week and then again, completely dead.

Local mechanic said charging system seemed fine and would do other tests. My wife figured the alarm was the culprit and asked them to yank out the brain...they did.

Never had a starting problem since then.

In your case, if the alarm has a faulty brain, it could be leaving an open circuit, obviously something that draws plenty of juice...I would have them yank the alarm computer out and swap it for another...if the problem persists, it will take diagnostics.

BTW 12.3V is low for your charging system, but not enough to suck your battery dry in a few hours...
2009 ML350 (84K) - Family vehicle
2001 CLK430 Cabriolet (71K) - Wife's car
2005 BMW 645CI (124K) - My daily driver
2012 Mustang V6 (60K) - Daughter's car
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Old 02-04-2002, 09:49 AM
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Get yourself a digital voltmeter - they are cheap. Check the voltage at the battery - car off - should be 12.56- 12.9V. If it is lower - put an automatic charger on battery until it shuts off. Measure the battery voltage - it should now be 12.56 or higher. Wait for an hour and check it again - if it is significantly lower - you have major voltage drain - suspect the alarm and or wiring of it. If the charger won't shut off automatically at all- you really are pumping a lot of current. Put the voltmeter on the battery and start the car - LEAVE ALL LIGHTS AND HEATER MOTORS OFF - The voltage should be MINIMUM 13.2 V but 13.4-14.2 indicates a good alternator output. If this voltage is not there - while engine is running - check the voltage at the output of the alternator itself - if it is 13.4 -14.2 there but not at the battery - CHECK YOUR WIRING. If it is not at the alternator - you probably need a new alternator.The digital voltmeter is indispensable for troubleshooting this kind of problem. JUST WONDERING GUYS - I have never done it - but if the installers of the alarm system shorted the output of the alternator to ground while the car was running - could they have shorted the diodes in the Alternator? If the diodes in the alternator are shorted - could they not then drain the battery as this fellow is experiencing? Is it possible???
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Old 02-04-2002, 11:10 AM
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Join Date: Jun 2000
Location: Saugus, CA USA
Posts: 1,974
Feel around for something hot, or warm. That amount of of current will get things pretty warm.
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Old 02-04-2002, 11:30 AM
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Join Date: Oct 2001
Location: Canada
Posts: 298
When I repaired the Becker 1432 on my 400E by myself, a stuck relay in the radio drained about 0.4 amps current, my battery ran out when I left the car in the garage over the weekend.

10 Amps is not a small current, 120 Watt in power, something may be fried by this, if the thing can constantly stand for such high power, it must be quite big in size so it can sink the heat. It's not likely that small alarm unit can stand for 120 Watt power, sounds like they screwed up your car when installing the alarm system, probably there is a short in the alternator.
99 BMW 540i 6-speed 110K Km
03 SAAB 9-5 wagon 80K Km
92 400E (Sold) 245K km
Still missing the days with the Benz, it kept me busy.
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Old 02-04-2002, 12:10 PM
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Join Date: Dec 2001
Posts: 565
Have read bits and pieces of this thread. Moedip may be on to something. If the ground strap was pulled with the engine running, the diodes in the alternator are most likely gone. This would explain 12.x volts with the car running.

There is no doubt that alarm systems in general draw juice from the battery; I'm not sure how an alarm could draw enough current in 4 hrs. to drain a battery.
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Old 02-05-2002, 04:30 PM
Posts: n/a
update again...

My benz is back at Circuit City for the fourth time. My mechanic deemed the alternator to be in good shape, since it's a newly rebuilt Bosch Alternator that was generating 13.2 - 13.5 Volts. The serpentine belt was fine, since mechanic said it was auto-adjusting. Mechanic also did a light bulb test on the battery when the car was off and the light came on - he said it shouldn't come on, it means current is going through. He also measured a current of 5.5 amps drawing from the battery when the car was off, but he didn't do anything more to find out what was drawing the current.

Mechanic suspects the alarm system, so the benz is back in Circuit City. I told them to take it out, but they wanted to diagnose it some more and they seem to be making some progress. They are checking every single wire now with other specialized technicians on the phone to guide them. To be honest, I would much rather them pull it out, but they insist that after all the hard work of installing it they want to try to find out where the current is being drawn. It's a Learn as you Work situation and my car is the Case Study. I wrote a nasty email to circuit city customer service and maybe I'll get all my money back. But this isn't the end of the story, my car is still in the service shop, so who knows...??? I'm so nice and patient to give them three chances....strike 4 they are out!
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Old 02-05-2002, 04:56 PM
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Join Date: Dec 2001
Posts: 565
Regarding the "light bulb" test with the car off. I assume you mean the mechanic pulled the battery ground strap, connected the clamped end of the test light to the ground strap, then hooked up the other side to the + terminal of the battery.

If you have an alarm, the light will illuminate. Alarm systems pull enough juice to light up 12v test lights all day long. The light bulb test was ok way back when. It does not apply to modern vehicles that have clocks, alarms, etc.
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Old 02-05-2002, 07:18 PM
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Unhappy Circuit City damaged my car...

I just heard back from Circuit City and after 9 hours of looking at my car, they could NOT figure out where the current was coming from. They took off the alarm system and still the current was there. So they definitely damaged my electrical system. But here's the good news....

They agreed to refund everything and also pay for any repair costs that resulted from their faulty installation.

Now my next feat is to find a reliable MB dealership or repair shop in my area to fix their mistake. I've already posted up that request in another forum, but if you know anyone off hand in Virginia Beach, Chesapeake, or Norfolk, VA, then please let me know.

I'm still not satisfied because I still don't have an alarm. I'm just glad that they admitted to their faults. I learned a lesson to be more cautious of who I let touch my benz.

Thanks everyone for your input/advice. I love this site! It's awesome!
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Old 02-05-2002, 07:37 PM
Registered User
Join Date: Dec 2001
Posts: 565
I would not worry about the alarm. In this world, there are car thieves who can get anything, anywhere; anytime. If they want it, it's gone.

The ONLY reason I have one is because the car came with it. The damn things suck current, even when they are performing as intended. Batteries will last longer without them.

My 2 cents.
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Old 02-20-2002, 04:04 PM
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Smile Final update...

My benz is back to normal. I took it to the MB dealership and they fixed Circuit City's mistake. It ended up being a $700+ fix to get my vacuum locks and factory alarm back to normal.

It turned out that Circuit City butchered up my wires pretty bad, broke two door actuators, caused multiple vacuum leaks, and wires were melted together at multiple areas. The MB Technician said I was lucky my car didn't catch on fire from the incorrect alarm installation.

LESSON LEARNED: Never go to Circuit City to have any alarms or stereos installed - they don't understand the complexities of a Mercedes! Go to the professionals or your local MB dealer!
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