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300SD Glow plug relay
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Posted 2/14/2011 9:51 PM
dmcginn2
Regular


Date registered: Apr 2007
Location:
Vehicle(s): 2007 ML 320 CDI
Posts: 61
50
300SD Glow plug relay

Question:

Bought a 300SD. Sunday night the glow plug relay went. There was a slight electrical burning smell outside but I thought it was my neighbor welding. When I came out in the morning, the battery was dead, and when I jumped it, I noticed the glow plug light was on when the key wasn't in in the ignition. Engine never started.

Tried disconnecting the power wire to the relay and manually turning on the glow plugs by touching the wire for 30 seconds. Still couldn't jump it. It does turn over.

Anyway, I am going to replace the relay, but did the glo plugs fry before the battery died?
#184897
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Author
Posted 2/16/2011 9:50 PM
dmcginn2
Regular


Date registered: Apr 2007
Location:
Vehicle(s): 2007 ML 320 CDI
Posts: 61
50
Re: 300SD Glow plug relay

I think I answered my own question. I found an old relay from the previous owners in my trunk, transferred the strip fuse to it, and tried it out.

It started right up maybe turned over twice.

Interestingly enough, the glow plug light did not come on...I know the bulb is not burned out since the burned up relay (actually melted) caused the light to stay on all the time.



#185013 - in reply to #184897
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Posted 3/22/2011 1:29 AM
rumpuscat
New user


Date registered: May 2010
Location: Tehachapi, Calif
Vehicle(s): Honda Civic
Posts: 2

Re: 300SD Glow plug relay

dmcginn2 - 2/16/2011 6:50 PM

I think I answered my own question. I found an old relay from the previous owners in my trunk, transferred the strip fuse to it, and tried it out.

It started right up maybe turned over twice.

Interestingly enough, the glow plug light did not come on...I know the bulb is not burned out since the burned up relay (actually melted) caused the light to stay on all the time.





Glow plug relay lights are set up to flash for a short time if one glow plug is bad and not light up at all if two or more plugs are bad.Also the relay could be defective causing to light to not operate.. An old analog ammeter capable of measuring 30-40 amps can be used to check all the glow plugs individually at the harness plug by using the power available at the relay fuse to the meter and the other meter lead to the individual plug socket in the connector. Watch for a current surge to 30 or so amps steadily declining to about 20 amps as the plug warms up.
#186717 - in reply to #185013
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