Hello!
I think I have a problem with my glow plug relay.
Hard starts in colder weather.
So I searched the forums and found a thread on troubleshotig the relay.
It is a 2001 F350 with the 7.3 motor.
Ignition off:
One big terminal 12v all the time.
Other big terminal 0V.
Two small terminals .8V
Ignition on with Wait to sart light lit
One Big terminal still 12V
Other big terminal still 0V.
Two small terminals 12V.
AhA!
Bad glow plug relay!
Other big terminal should be 12V when ignition switched on according to the forum thread I found.
I pulled the relay and replaced with new one.
Absolutely no changes on the voltage readings...
Still 0V on big terminal with key to ignition.
What am I missing guys?
Is there a bigger problem?
Disconnect the two small terminals and determine which one is the "hot" positive side when key is on. Reconnect that one and then run a new separate ground to the other side. The relay should now work. Problem could be an open circuit in the harness, and not the PCM.
So that must mean somehow the ground from the pcm isnt getting to the small terminal.
I was planning on running a ground to the terminal on the pcm that outputs the ground.
If the relay clicks on then i know the wiring is good and the pcm is bad.
Only problem is that i have no idea where the pcm is.
I have a diagram showing which wire on the pcm outputs the ground...i just need to find it.
Also...does the pcm ever NOT send the ground? Like if your engine is hot?
Hello there, this is not really a reply more of a question. I’m having the same issue with my new relay Not working. So the question is can The relay we put in Either way as in power from the battery can go to either post on the relay, does it matter? The two little connections is one a specific ground? Or again doesn’t matter which wire goes to which little connection?
Those little wires go to an electromagnetic coil inside the relay which, when current is flowing through it, moves an iron slug and that motion closes the contacts to activate the plugs. This is DC current so, it will create that magnetic field no matter which way it flows through it...
Check the seal inside of the plug. These come out of place and keep the plug from engaging all the way. The PO of my truck had the entire left bank og glow plugs and harness replaced, still threw the gp codes, I pulled the controller and, also, looked in side the plug.... Sure enough, that seal had pushed down inside the plug and it wouldn't connect all the way.
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