When putting the glow plug relay on a switch, is it better to break the 12v side of the coil, or the ground from the pcm?

 

Leave the PCM ground in tact.

I've got my GP relay switch that adds the ground. One pole on the switch goes to the GP relay and the other pole on the switch goes to a ground. That way the PCM can still control the GP relay in a normal way and I can over ride it and activate the relay when I want it too.

 

I want to do just the opposite with mine. I want shut the relay off after the truck is started rather than let the glow plugs stay on for a long period when not needed.

 

In your '97?

The '97 PCM programming is VERY short with the GP relay. My '97 doesn't even hardly activate, even in the middle of the winter. I've had to use my switch more times than not in the winter and I have no problems with any of my sensors or my PCM.

 

GP's on mine stay on up to two mins and mine is a 97

 

Yeah, it's for the '97. The WTS start light goes off in a couple seconds, but you can watch the volt meter, and the GPs stay lit for long time. I haven't timed it, but it has to be a minute or more.

 

I have a wiring diagram somewhere to turn off the gp. I will find it and send you a copy.

 

Mine cuts out pretty quick.

 

My switch in the off position lets the PCM do its thing normally. After the first start of the day I flip mine off so the GP's can't run. I just feel its a waste of energy and wear and tear on the GP's to let them run when the motor starts fine without them. This is mostly for short trips around town when the OT doesn't get up there to stop them running.

 

Do you have a diagram of how yours is wired up?

 

Here is a link for manually controlled GPR from last year
https://www.ford-trucks.com/forums/1...g+relay+switch

 

Thanks Randy. I figured I'd just break the ground at the coil side of the relay....switch on, the GPs work.....switch off, they don't.

 

Thanks Rich. That's pretty much what I had in mind, but I'll have the swith between the violet wire and the relay. I just didn't know if it would be better to break the ground or the 12v side of the coil.

 

The info I have did it like the link Rich posted.

 

I wonder if there is a reason for doing it that way rather than just breaking the violet wire with the switch.