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  #16  
Old 04-04-2010, 09:34 PM
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I would first pull the reg out (2 screws ) replace the plug in the alt & see if the light is on. If its not then chances are the reg is bad. if its on then reg may be good & alt is bad.
I once had an insect get in the back of the alt, it got fried & then the alt light just glowed dim all the time.
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I no longer question authority, I annoy authority. More effect, less effort....

1967 230-6 auto parts car. rust bucket.
1980 300D now parts car 800k miles
1984 300D 500k miles
1987 250td 160k miles English import
2001 jeep turbo diesel 130k miles
1998 jeep tdi ~ followed me home. Needs a turbo.
1968 Ford F750 truck. 6-354 diesel conversion.
Other toys ~J.D.,Cat & GM ~ mainly earth moving
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  #17  
Old 04-04-2010, 10:21 PM
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How does your post #5 determine if the alt or the reg is bad? Or are we just to replace both & keep our fingers crossed?

If there was a problem with power getting to the ignition side of the switch (loom problem) and the alt/reg were good, the light would go out as you described.

Given that the OP said that he had replaced the reg some time ago, I am left wondering why 2 regs may go bad. Is there some other problem?

If the alt is bad, it may be the second set of diodes (exciter diodes) that are the problem. There may be some foreign object lodged in the alt doing it.

It may not be as simple as we may want it to be. I have seen plenty of so called "bad " alt's that people have paid a lot of money to replace, with very little, if anything wrong with them. Too many just start replacing stuff until the problem goes away!! Pars suppliers love that approach.

Maybe we all need to "Look Listen & Learn" !!!!!
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Grumpy Old Diesel Owners Club group

I no longer question authority, I annoy authority. More effect, less effort....

1967 230-6 auto parts car. rust bucket.
1980 300D now parts car 800k miles
1984 300D 500k miles
1987 250td 160k miles English import
2001 jeep turbo diesel 130k miles
1998 jeep tdi ~ followed me home. Needs a turbo.
1968 Ford F750 truck. 6-354 diesel conversion.
Other toys ~J.D.,Cat & GM ~ mainly earth moving

Last edited by layback40; 04-04-2010 at 10:47 PM.
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  #18  
Old 04-05-2010, 09:46 PM
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Location: High Point, NC
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Well,
I tried replacing the voltage regulator today with no success or change in the problem. It looks like I am on my way to a new alternator unless anyone else has any ideas. I really do appreciate all of the help. I do need new belts anyway.
Thanks
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  #19  
Old 04-05-2010, 10:04 PM
layback40's Avatar
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Maybe the last reg replacement was just hiding a alt on the way out?

A new alt/reg is the next step.

Your old reg maybe ok but I dont think you want to take the risk.

Make sure you get a new one or a good quality re-manufactured one. I think it is worth inquiring on this site, Fastlane Phil has been very competitive in the past.

You could also look at an upgrade to a higher amperage alt.

Good Luck!!
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Grumpy Old Diesel Owners Club group

I no longer question authority, I annoy authority. More effect, less effort....

1967 230-6 auto parts car. rust bucket.
1980 300D now parts car 800k miles
1984 300D 500k miles
1987 250td 160k miles English import
2001 jeep turbo diesel 130k miles
1998 jeep tdi ~ followed me home. Needs a turbo.
1968 Ford F750 truck. 6-354 diesel conversion.
Other toys ~J.D.,Cat & GM ~ mainly earth moving
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  #20  
Old 04-05-2010, 10:25 PM
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Join Date: May 2004
Location: Sunnyvale, Texas (DFW)
Posts: 9,673
Quote:
Originally Posted by partsman225 View Post
i been working on mb's for 27 years i think i know when i see a bad alt. its not the first time i seen this . well good luck !

you can thank me when you're done

Some folks just need the affirmation of "credit due"....
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'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John
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  #21  
Old 04-05-2010, 10:34 PM
layback40's Avatar
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Location: Victoria Australia - down under!!
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Best let high balls go through to the keeper !!
__________________
Grumpy Old Diesel Owners Club group

I no longer question authority, I annoy authority. More effect, less effort....

1967 230-6 auto parts car. rust bucket.
1980 300D now parts car 800k miles
1984 300D 500k miles
1987 250td 160k miles English import
2001 jeep turbo diesel 130k miles
1998 jeep tdi ~ followed me home. Needs a turbo.
1968 Ford F750 truck. 6-354 diesel conversion.
Other toys ~J.D.,Cat & GM ~ mainly earth moving
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  #22  
Old 04-06-2010, 10:57 PM
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Join Date: Mar 2007
Location: High Point, NC
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Straight From Bosch

I picked up a remanufactured Bosch alternator today and rather than going through all of the effort of installing it first, I just plugged it in to the harness and surprise, the light on the dash did not come on. The problem indeed seems to be a bad alternator. The new alternator came with a little manual and right in it is says "Alternator warning lamp comes on with the ignition switch turned off: If this situation occurs, there is a bad diode in the alternator...remove and replace the alternator." Man, I wish I had seen that about two days ago. I am going to replace the alternator tomorrow night and do all new belts at the same time. Anyone have any special tips about the belts or alt? I am about to search the archives to see what others before me have had to say. I appreciate all of the help and I hope this thread can help others with the same problem.
Thanks!
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