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  #1  
Old 06-18-2008, 06:01 PM
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All power does not disconnect when key is turned off

Anyone have a suggestion as to why some of the curcuits would still be hot even with the key off? I've changed the electrical portion of the ignition switch, but that was not the problem. I'm changing and checking fuses, etc trying to find out what the cause is.

Battery, brake, and brake pad wear indicator lights stay on when the key is turned off. Thanks. KRW

ps. The car is an 83 300D Turbo Diesel Sedan
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  #2  
Old 06-18-2008, 07:55 PM
RAYMOND485
 
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Alternator Light On Key Off

1984 300d Turbo 147k
Pull The Plug On The Alternator, Check If The Warning Light Is Off
Its The Diode In The Alternator, Replace Alternator
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  #3  
Old 06-18-2008, 08:11 PM
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Quote:
Originally Posted by RAYMOND485 View Post
1984 300d Turbo 147k
Pull The Plug On The Alternator, Check If The Warning Light Is Off
Its The Diode In The Alternator, Replace Alternator

Or, just replace the regulator. Only one plug and two screws. $30-40 bucks.

Jim
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  #4  
Old 06-18-2008, 11:01 PM
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The alternator is a Bosch 115 amp unit off of a late 80's model SAAB. It bolted right up. However, it is not just the battery light that is staying on. There is also the brake light and a few of the accessories, but not all.

Also, when the car starts, everything is working normally. But when I turn off the engine and remove the key, the indicator lights come on and the aux fan will keep running as well (if the engine is warm enough).

Thanks for your help. I will check the alternator and make sure the voltage is correct. KRW
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  #5  
Old 06-19-2008, 01:22 AM
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Check the fuses?
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  #6  
Old 06-19-2008, 02:04 AM
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Quote:
Originally Posted by krwsenior View Post
Anyone have a suggestion as to why some of the curcuits would still be hot even with the key off?
A number of circuits are "Hot at all times" by design. Turning the key off will have no affect on those circuits.
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  #7  
Old 06-19-2008, 10:20 AM
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All current is not shunted through the key switch electrical contacts on a lot of cars. . There might be a load relay that has stuck or welded contacts. Does anyone remember if these cars have one? The key switch normally turns a cars load relay on and off again if it has one. At this point if there is one in your model it is the best suspect. Does this jog anyones memory?
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  #8  
Old 06-19-2008, 10:41 AM
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Quote:
Originally Posted by JimFreeh View Post
Or, just replace the regulator. Only one plug and two screws. $30-40 bucks.

Jim
Not on an 83 not part of the brush pack
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  #9  
Old 06-19-2008, 11:33 AM
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Quote:
Originally Posted by JimFreeh View Post
Or, just replace the regulator. Only one plug and two screws. $30-40 bucks.

Jim

Quote:
Originally Posted by TX76513 View Post
Not on an 83 not part of the brush pack
How many screws and plugs on an external regulator?
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  #10  
Old 06-19-2008, 11:45 AM
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Quote:
Originally Posted by tangofox007 View Post
How many screws and plugs on an external regulator?
Pic of external regulator

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  #11  
Old 06-19-2008, 02:05 PM
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Quote:
Originally Posted by barry123400 View Post
All current is not shunted through the key switch electrical contacts on a lot of cars. . There might be a load relay that has stuck or welded contacts. Does anyone remember if these cars have one? The key switch normally turns a cars load relay on and off again if it has one. At this point if there is one in your model it is the best suspect. Does this jog anyones memory?
This is a great thought. According to the FSM, the aux fan does have a relay, which could be sticking on when it gets hot. The switch contacts in the relay come from a fuse that is hot at all times (can't read the fuse #, CD-ROM has insufficient resolution).

Aha! Page 108 of the circuit diagrams in the FSM [attached] shows that the charging light and the brake warning lights are interconnected through the "warning system," a complicated electronic relay that involves the door-open, key-in-ignition, and seat-belt buzzer. The warning system is a little metal box located under the dash and just to the right of the parking brake pedal. I can't find its schematic in the FSM; the index says "next index" and then the next index says "previous index."

If I had to take a guess, I'd replace that warning system thing. I had a problem with the analogous module in my '87 300D-T (W124, OM603) in which all kinds of screwy things were wrong in the dash. Replacing the warning module fixed the problems.

Jeremy
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  #12  
Old 06-19-2008, 02:12 PM
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It's the backout diode inside the alternator on the inner diode plate. When it fails it allows power to flow back through the system that's why you are getting some idiot lites illuminated with key off.
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  #13  
Old 06-19-2008, 03:08 PM
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On my american car, when the regulator failed like this, the alt. would get warm, and pull a wrench to it with a magnetic field in the alt.
Was a quick easy check. Whould be the same here right?
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  #14  
Old 06-19-2008, 03:43 PM
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Thanks so much for the info. I will check these things tonight and post what I find. KRW
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  #15  
Old 06-19-2008, 08:30 PM
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More Clues!!

When I turn the key on, then off again, the following 6 circuits stay hot when they are not supposed to.

10 - heated rear window
12 - stop lamp, turn signal lamp, inst cluster, cruise control, (relay window lift term. 86, tachometer)
14 - back up lamp, warning monitor term 8, emission control, horn, overload protection (autom transmission, relay auxillary fan term 86, control unit/water pump/heating water valve for climate control system)
a - (window lift front right, rear left)
b - (window lift front left, rear right)
d - (sliding roof)

I also find that if I disconnect the battery, then connect again, these circuits stay off (as they should) until I turn the key on. Then when I turn the key off, they all stay on. I also disconnected the wires leading to the warning contol box under the dash and nothing changed. Same problem either connected, or disconnected from the warning box.

I can't figure out what is causing it but it acts like a relay of some kind. I think this because when the battery is disconnected, the circuit breaks until the key is turned on again.

(I have already changed the electrical portion of the key switch, but I'm wondering if the new one is bad too). KRW
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