I have the Mercedes CD repair manual for my 82 300 SD. I also have reviewed the postings concerning the glow plugs and the relay associated with them, but have still come up with some questions pertaining to the glow plug/relay system. This is my first time asking for help from this forum. With that being said, I will describe my situation.

On cold mornings I am having difficulty starting my car if I do not plug it in overnite. I have measured the resistance of each individual glow plug with the connector disconnected at the relay on the driver side wheel well. According to the spec. in the manual, I should be seening 1 ohm or less for each of the glow plugs. My measurements ranged from 1.2 ohms to 2 ohms. I concluded that the glow plugs are suspect and I have ordered a new set. I also checked for voltage at each glow plug and found that I have approximately 10.5 volts at each glow plug. While performing this check, I realized that the relay is only staying engergized for about 2 to 4 seconds total. This is verified by the voltmeter going to 0 volts after I hear the relay open up. I have been noticing over time that the glow plug indicator light on the dash panel has been going out more quickly over time (i.e. staying on for a shorter and shorter time).

My question is this: Is there a relationship between the glow plugs degrading over time and the glow plug indicator light illuminating for a shorter amount of time.

Also, is this an indication that the relay is starting to fail, or does the relay have a hard failure, as in it works or does not work.

Any help will be appreciated.

Thanks,

Rob

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'82 300SD 206K miles Anthracite Grey received 250,000 Km badge
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