Glow plug relay problems help?

[Pstroke32]

2000 f250 installed new relay since it was not transferring any voltage across the post when key turned on, well new relay is on and same problem. I was told the computer might not be grounding the relay out, and that it was a computer issue.
Any help would be much appreciated.

 

[Arisley]

Time to chase wires.

 

[bruce]

If you're putting both test leads on each of the posts then its gonna read 0 volts DC. You are going from ground to the post right?

 

[Pstroke32]

I am testing DC volts and I'm going off my battery ground with my one lead to check voltage. I have someone in the cab turning key to cycle glowplugs and the constant 12 volts doesn't transfer over to the other post during glow plug cycle.

 

[bruce]

Are you getting any power at the exciter wires? Probably not since this is the second relay you've tried. Yep time to pin out some harnesses

 

[Pstroke32]

I put my lead on the post, no power. However .032 read on my tester when I put the lead on the wires heading to glow plugs. Idk I guess it's wire tracing time.

 

[Clem1226]

Someone refresh my memory here, what does the PCM use to determine if it is going to cycle the glow plugs, EOT and Ambient air temp or just EOT or something else?

For the OP

Four posts on the GP relay. One big post has 12VDC one connects to the GPs. One small post has 12VDC with the key in the run position and the other is connected to the PCM and receives a "voltage low" trigger signal when the PCM commands the GPs on. Make sure you have 12vdc at the small terminals (with the key in run position)and if you do either the PCM is not commanding the GPs on or you have a broken wire.