Glow Plug Relay Repair

antennaclimber

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My M1009 became increasingly hard to start when the glow plugs were needed to be on. Finally one morning it wouldn't start at all. Batteries are good, glow plugs are good and my GP card is good, relay made normal noise when closing.

After getting a volt meter from my work truck, found that I had nominal
12 volts at the top terminal of the relay and next to nothing at the bottom terminal. So the glow plugs were not getting any voltage and thus the reason for no start.

I went to NAPA and purchased a ST85 relay. Installed it and the truck starts fine.

Wondering why the relay failed, I opened the relay it and found out why.
Simple reason is dirt. One of the contacts had accumulated a considerable amount of dirt and this was causing enough resistance under high current load to have a low voltage at the lower terminal.

I cleaned (wire brushed) all the contacting surfaces inside reassembled the unit and tested for proper operation.

Once again we can see why high current loads require clean and tight contacts.
Attached are pictures for your enjoyment.
Karl
 

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Warthog

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Once again Karl has the solutions. Thanks.

How did you open the relay and reseal it?
 

antennaclimber

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I used a vise to pinch the top off. It popped right off and was only slightly distorted.
Reinstalling the top was done with the universal BFH.

I should seal it a little better, with some waterproofing materials, but for now it will be a spare unit.
 
Last edited:

doghead

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Did you refill it with magic smoke?
 

cpf240

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Is that just dirt, or is it carbon from the contacts arcing? Are your glow plugs running stock 24v or the 12v bypass?

My relay stopped providing power to my glow plugs shortly after I did the 12v bypass for the glow plugs. I assumed it was due to carbon build up that resulted in increased resistance at the contacts. I did not take apart the relay though. I'll have to see if it is still in the junk box.

Thanks for the pics!
 

Keith_J

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Round contactors are supposed to rotate, looks like this one didn't. It happens, had it on a M35A2 starter. Clean and reassemble. Use as a backup only.

I've yet to see a part number for magic blue smoke aua
 

antennaclimber

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Dang!
Forgot to refill the smoke.

Looks like the contactors did not rotate and I agree with cpf20, carbon build up on the contact surfaces. The copper had no noticeable pitting of the mating surfaces.

The truck has been modified with the resistor bypass. The GP's are fed with 12 volts.

Mfg date on the relay was 1993.
Karl
 

forest522

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I used a vise to pinch the top off. It popped right off and was only slightly distorted.
Reinstalling the top was done with the universal BFH.

I should seal it a little better, with some waterproofing materials, but for now it will be a spare unit.
We have BFRs in Oregon. Guess its the tool-less redneck heritage or something...no tool, find a rock!
 

tbearatkin

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Electricity 101:

Positive ground depends upon proper circuit functioning, the transmission of negative ions by retention of the visible spectral manifestation known as "smoke". Smoke is the thing that makes electrical circuits work; we know this to be true because every time one lets the smoke out of the electrical system, it stops working. This can be verified repeatedly through empirical testing. When, for example, the smoke escapes from an electrical component (i.e., say, a Lucas voltage regulator), it will be observed that the component stops working. The function of the wire harness is to carry the smoke from one device to another; when the wire harness "springs a leak", and lets all the smoke out of the system, nothing works afterwards. Starter motors were frowned upon in British Automobiles for some time, largely because they consume large quantities of smoke, requiring very large wires.
 

doghead

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In conclusion, the basic concept of transmission of electrical energy in the form of smoke provides a logical explanation of the mysteries of electrical components
 

sierrajcharlie

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It has been explained to me that it is not actually magic smoke that escapes when something electrical ceases to function properly. When something expires, regardless from natural causes or having been murdered. What you see is actually it's spirit being released.
I just thought I would share this in an attempt to dispel the myth of the magic smoke.
 

MarcusOReallyus

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Electricity 101:

Positive ground depends upon proper circuit functioning, the transmission of negative ions by retention of the visible spectral manifestation known as "smoke". Smoke is the thing that makes electrical circuits work; we know this to be true because every time one lets the smoke out of the electrical system, it stops working. This can be verified repeatedly through empirical testing. When, for example, the smoke escapes from an electrical component (i.e., say, a Lucas voltage regulator), it will be observed that the component stops working. The function of the wire harness is to carry the smoke from one device to another; when the wire harness "springs a leak", and lets all the smoke out of the system, nothing works afterwards. Starter motors were frowned upon in British Automobiles for some time, largely because they consume large quantities of smoke, requiring very large wires.
In conclusion, the basic concept of transmission of electrical energy in the form of smoke provides a logical explanation of the mysteries of electrical components

Y'know, I gots me one of them thar DEEgree thingies in electrimocity, and I can't argue with any of that! :mrgreen:
 

doghead

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The relay should be listed in the stickies.

st85
gpr109

It must have 2 small terminals and they must not have continuity to the mount.

Test whatever you buy, to confirm this, before installing it.
 

twomorestrokes

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thanks again.when I call the auto parts stores just asking for a glow plug relay I get quoted 19 dollars. When I specifically asked for an ST85 it is 60 dollars. Is it worth the extra cash?
 

doghead

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Your call. I have no idea what they are offering you for $19.

Test and confirm whatever you buy.
 
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