Had a hard start yesterday; knew something was going on with the glowplug system as the glow plug light on the dash wouldn't light up every time I turned the key.
I put a new fuse in cause I had one and they're cheap.
Then I searched here & read that the light won't work if there are two or more plugs not working. I pulled the harness plug from the glowplug controller on the driver's side fender wall just behind the headlight to test my plugs, connecting one probe of my multi-meter to the battery ground and the other to each of the five numbered ports. (I also checked voltage at the pins on the controller to be sure they were getting 12V when the key was at the #2 position - they were, so the controller is good)
Here's the readings I got:
1- 202
2- 0.8
3- 220
4- 0.8
5- 0
I will pick up three new Bosch plugs today at Autozone.
I am wondering why all three went bad all of a sudden as the car always fired immediately every cold start before yesterday

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Jeff
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1982 300D Turbo 150K
PlantDrive Single tank WVO conversion
6000 veggie miles and counting!
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1985 Ford F250 - 132K
PlantDrive Two-tank WVO conversion
15,000 veggie miles and counting...

Driving for FREE!

Doesn't bad things happen in threes?

Veg,

Are you sure you don't mean infinite resitance for #5 GP. Its almost impossible to get 0 ohms because there is always the contact resistance and resistance of the wires. If there was 0 ohms (short circuit) the fuse in the GP relay should melt and open the circuit.

To get 2 GP with readings of about 200 ohms is weird. Did you try connecting these 2 GP to the battery to determine if they glowed?

P E H

...........further supporting the case that a glow plug is not a light bulb.

At work we don't do ohms tests on glow plugs. We just scratch a jumper from the battery to each plug (unplug the connecter of course) if it sparks..good injector, if no sparks...bad injecter. On my car the light would not come on after 2 glow plugs failed.
Not sure if it's my controller though but lately the glow plugs work great in the morning but after the car sits in the sun all day they won't work and the car cranks a bit before starting. I'll look into that another day.

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83 300sd
3 Fords

Probably 3 didnt go bad at once. It just started ok with 1 bad, then 2 bad. The same thing happened to me 2 weeks ago. The part store I use only sold them in fours !! So my glow plugs are 80% replaced.

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1959 Gravely LI, 1963 Gravely L8, 1973 Gravely C12
1982 380SL
1978 450 SEL 6.9 euro restoration at 63% and climbing
1987 300 D
2005 CDI European Delivery
2006 CDI Handed down to daughter
2007 GL CDI. Wifes