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  #1  
Old 05-18-2006, 07:50 PM
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300sd light for glowplugs do not work

When I turn the key on my 300sd 1985. The light on the dash does not come on. My glowplugs are not working,I have not checked the fuse yet. Is there anything else I need to check? thanks

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  #2  
Old 05-18-2006, 07:56 PM
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Normally, when all plugs go out, it's the fuse.

If not, then the relay might have bit the dust.

Usually one or the other.

One is $1.00........the other is............
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  #3  
Old 05-18-2006, 08:07 PM
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Where is the relay in the fuse box?
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Old 05-18-2006, 08:08 PM
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Quote:
Originally Posted by dave300d
Where is the relay in the fuse box?
The relay is not in the fuse box.

It's a black box on the driver's fenderwell, forward side. It will have a five pin connector in the side that leads to each of the glow plugs.
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  #5  
Old 05-18-2006, 08:22 PM
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I found the relay,it is 3 by 3 inches.Where is the fuses for the glow plugs.I looked in the fuse box but it did not list a fuse for glow plugs.
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  #6  
Old 05-18-2006, 08:35 PM
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check this out.

http://dieselgiant.com/glowplugrepair.htm
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  #7  
Old 05-18-2006, 08:41 PM
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Thanks------------
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  #8  
Old 05-22-2006, 08:24 PM
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This morming i turned the key and the light did not come on.I turned the key off and then back and the light came on. Had to preheat 2 times and light worked both times. Latter in the day the light did not work the first time--but the second time it did.Any ideas why it would work the second time?
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  #9  
Old 05-22-2006, 11:45 PM
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Quote:
Originally Posted by dave300d
This morming i turned the key and the light did not come on.I turned the key off and then back and the light came on. Had to preheat 2 times and light worked both times. Latter in the day the light did not work the first time--but the second time it did.Any ideas why it would work the second time?
Whenever the light is intermittent, it's usually a sign of one or two bad glow plugs. The engine starts OK in warmer weather, but, you'll have trouble with it when it gets cold again.

Do a resistance test of each glow plug via the harness and confirm which one's are NG.
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  #10  
Old 05-23-2006, 12:04 AM
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I have a glowplug light issue too...

My GP light rarely ever comes on. Sometimes, it will come on after I have warmed the engine, turned it off, and then on again. Even then, it stays on for about five or so seconds.

Each one of my glowplugs has been tested and they are all showing < 1 amp. My GP relay also makes the click noise after about thirty seconds.

I live in a warm climate (Southern California), and I've heard that the later diesels are "smarter" and that they minimize GP heat up time according to the temperature. Is this true?
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Old 05-23-2006, 09:07 AM
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Less than 1 amp or less than 1 ohm? Should read about 0.6 ohms cold on a good glowplug.

Len
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Old 05-23-2006, 10:08 AM
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Oops, I meant ohm.
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  #13  
Old 05-23-2006, 10:35 AM
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A better test of (parallel style) glow plug health is a current draw reading. But you need a DC ammeter capable of 20 amps to do this. Ohm readings are good but can miss a partially broken, poorly heating glow plug.

The real definitive test is to pull them all out and apply 12 volts to them (individually) and watch them glow red. I had one that was partially broken such that it would draw about half the normal current - it would not glow bright red.

However, this is a dangerous test to the extent that you can severely burn yourself if you touch the hot glow plug to your skin or other internal and external organs. Only a professional should do this test, do not attempt to repeat this test at home. Etc. Etc.

Ken300D
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  #14  
Old 05-23-2006, 07:56 PM
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That is what I am thinking.It starts harder than normal. Thay is a good way to check them-pull them out and turn the key and see what one turn red.

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