does anyone know what the voltage that should be running through the glow plug relay?? when i turn my key on there is only 8.6 volts running through.

 

That sounds like your batteries are weak. What do the batteries read when you have the glow plugs energized? Usually a 1-2 volt drop is all that is noticed.

 

X2.... I think you may have a battery problem. Are you getting 12 volts on the hot side of the relay?

 

battery is 12.08 when i cycle the glow plugs the battery dropes to 11.88

 

When the relay is energized, you should have battery voltage on the GP side. If not, then your relay is robbing voltage somehow. If you have the AIH relay, then you can try swapping it out with the GP relay and see if your voltage readings are better. Here are some readings from my truck taken earlier this year...

 

I just installed the new glow plug relay! Will have to wait till tomorrow morning when it's cold!

 

Hey I am not trying to hijack this thread or anything, but my glow plug relay is shot in my truck, I picked up a new one, but I think it is slightly different then the old one. On the two little leads, there is an I and an S, on the new one they are in a different spot then they are on the old one. I will try and get some pictures of it tomorrow, and maybe I can finally get my glow plugs working again.


Dennis

 

It could be the relay. Look at the pictures below. This one was cycling fine, but no voltage. When I tore it apart I found out why, yours could be similar to this and just creating too much resistance which drops the voltage.

 

94 white f250 sounds like you have a starter selinoid your year truck has a fender mount one that looks just like a gpr how much did you pay for it a gpr cost about 70-90 bucks and the starte selinoid coast 20-30 bucks hopes this helps i think this is the problem only cause it happened to me

 

Rus, If you are measuring voltage "across" the relay, you should see something like 1V when it is energized. There should be 0V between the glow plug side of the relay and "ground" when not activated, and somethign near 11.5 volts to ground when energized.

 

Replaced the relay yesterday and it fired right up this morning!!:-) first time in 4 months!!

 

Thanks for the follow up. Good to hear that you got it fixed.