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Car Forum / Mercedes-Benz Cars / July 200886 300SDL disabled alarm now car won't start
The alarm system on my 86 300SDL was hypersensitive, so I disconnected it by unplugging the two black connectors to the alarm controller, under the passengers foot rest. I first unplugged the smaller (lower) one, but that caused a lot of clicking after a while, so I ended up unplugging both. This was 2 days ago, and I was able to start and drive the car that day. But today it won't start - barely cranks and glow light/buzzer is fairly dim. I thought the battery was dead, but other things (headlights) work fine, not dim at all. I'm thinking now that I screwed up something in the alarm controller which blocks the ignition system. Is there any way I can bypass that completely to start the car, which I need to do to avoid being towed tomorrow? Is there a way to reset the alarm system so it won't block the ignition? I tried reconnecting the controller and locking/unlocking many times, but that didn't work. Thanks. > The alarm system on my 86 300SDL was hypersensitive, so I > disconnected it by unplugging the two black connectors to the alarm [quoted text clipped - 12 lines] > reconnecting the controller and locking/unlocking many times, but that > didn't work. Thanks. I looked at the schmatics and can't find anythine in the alarm system that would prevent the car from starting or running. I believe you must have an unrelated problem. Check the battery cables and ground straps between the engine and body. Paul Agree. The alarm has nothing to do with the starting system. MB's alarm system around that time monitors only the entry (4 doors, hood, I don't remember about the trunk) and anti-towing. Later models from mid-90 start to use ignition-disabler. The no-start must be the battery. The two most battery-draining tasks on a diesel are the preglow and starter. Both are needed to start the engine. This is why the battery for diesel needs more CCA than the gasoline engine on the same body. Believe it or not, the battery that cannot start my 87 300SDL can still be used in my 89 300TE (though barely making another year). >>The alarm system on my 86 300SDL was hypersensitive, so I >>disconnected it by unplugging the two black connectors to the alarm [quoted text clipped - 18 lines] > straps between the engine and body. > Paul Battery is highly suspect if > 4 years old. That it cranks at all excludes ignition / alarm system. Battery.  Signature© 2008 T.G.Lambach. Publication in any form requires prior written permission. Thanks folks will try replacing battery tomorrow, I am due for a new one anyway. I still suspect that my disconnecting the alarm had something to do with battery drain. I am wondering if I did some damage to the electrical system? I understand there's a relay in the alarm control unit that could be faulty, if it were stuck could that cause low voltage to the starter? I've had the car for 8 years and this is the only time it's not started. Re: alarm system, is it ok for this model to disconnect both connectors to the alarm control unit to disable the alarm? 1986 300SDL 150K miles. Jim ps, I'm thinking of selling this car because i only use it a couple of months every summer. Good condition, no rust, located Vermont, will sell for around 5K? I would have no qualms about driving this car to Patagonia and back. On Jul 28, 5:42 pm, "-->> T.G. Lambach <<--" <"T.G. Lambach at NoHamorSpamcomcast.net"> wrote: > Battery is highly suspect if > 4 years old. That it cranks at all > excludes ignition / alarm system. Battery. > -- > > © 2008 T.G.Lambach. Publication in any form requires prior written > permission. Thanks folks will try replacing battery tomorrow, I am due for a new one anyway. I still suspect that my disconnecting the alarm had something to do with battery drain. I am wondering if I did some damage to the electrical system? I understand there's a relay in the alarm control unit that could be faulty, if it were stuck could that cause low voltage to the starter? I've had the car for 8 years and this is the only time it's not started. Re: alarm system, is it ok for this model to disconnect both connectors to the alarm control unit to disable the alarm? 1986 300SDL 150K miles. Jim ps, I'm thinking of selling this car because i only use it a couple of months every summer. Good condition, no rust, located Vermont, will sell for around 5K? I would have no qualms about driving this car to Patagonia and back. On Jul 28, 5:42 pm, "-->> T.G. Lambach <<--" <"T.G. Lambach at NoHamorSpamcomcast.net"> wrote: > Battery is highly suspect if > 4 years old. That it cranks at all > excludes ignition / alarm system. Battery. > -- > > © 2008 T.G.Lambach. Publication in any form requires prior written > permission. I would also strongly suspect the fuses are slightly corroded. It is cheap to replace them. This would account for a lot of bizarre gremlins. |
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