glow plug relay shutoff switch...

JohnT24 · Apr 24, 2017

Just replaced my GPR for maybe the third time since I've owned the truck new in 95...

This time the hot wire post was getting smoking hot....
replaced it and all is fine again..

But,
I never liked the way the GPR stays ON for so long after the truck starts....
just watch the battery gauge..

So tell me if I'm nuts,
Heres my idea...

I run a battery shut off switch through the firewall to the dash where I can reach it conveniently. cables go to the relay/battery wire.

start the truck:

switch ON relay power
turn key/wait to start
start truck

turn off switch.

OR,
switch ON power
wait to start...

turn off power so starter gets full power...
start truck.

either way, when the truck starts, you kill the power to the relay... possibly saving the GPR and the glow plugs un needed use.

If you happen to leave the switch on, no problem... the truck justs acts like it normally would.

Do you see any flaws in my thinking here?

JohnT24 · Apr 24, 2017

I've seen the manual relay switches,
but I'd rather keep the truck on the factory system ... (wait to start light)

just kill the live power lead to the relay... instead.

Bugman · Apr 24, 2017

Why not just get a relay that will stand the use that our glow plugs draw from it?

I have had a Stancor which is White/Rodgers now for over 17 years with zero problems with it. Others have had good luck with a relay from Western Snow plows. If you do a search you should come up with part numbers for either one of them.

The design of the relay where it stays on for up to 2 minutes after starting is to burn off excessive carbon build up that happens on a cold engine possibly causing problems removing them. At least that is what the factory manuals say.

Why over complicate things by putting a switch into the system?

JohnT24 · Apr 25, 2017

Thanks.

Why?

Only because I have the cable/switch handy.

Ive read about the carbon
I still think its excessive time to be on.

Sent from my iPhone using Tapatalk Pro

JohnT24 · Apr 25, 2017

Actually I'm thinking
A smarter way to do it would be to use a second heavy duty relay and then a toggle switch on the dash

Sent from my iPhone using Tapatalk Pro

8WR_ZJ · Apr 25, 2017

On my old idi i have a contant ooen switch to trigger the relay then to the gpr. Push for 7 to 15 seconds then start.

Sent from my SAMSUNG-SM-G891A using Tapatalk

JohnT24 · Apr 25, 2017

8WR_ZJ said:
On my old idi i have a contant ooen switch to trigger the relay then to the gpr. Push for 7 to 15 seconds then start.

Sent from my SAMSUNG-SM-G891A using Tapatalk

Yeah
I'd rather retain the stock system
With the wait to start light
It works fine... just stays on too long.

Sent from my iPhone using Tapatalk Pro

8WR_ZJ · Apr 25, 2017

Yes i too wantes to retain the WTS start light. I only removed one wire and added a wire to the gpr. My wts light comes on when i hold the button. But after reading your post i think you are wanting to manually control the factory system correct. Let it do its thing for say 1 minute then kill it? I live in lake charles la on the coast cold weather is a non issue so i usually on have to do a 7 second burn then start and drive. When it gets below 32 degrees i do 12 sec, start, wait 30 sec, then 12sec again. you want that funtion just automatic right?

Sent from my SAMSUNG-SM-G891A using Tapatalk

JohnT24 · Apr 25, 2017

Not really
I simply want to cut the power to the relay as soon as the truck starts.

The factory wait to start light always seems to be pretty correct as far as time.
I'm happy to let it do it's thing.

I just hate driving a half mile down the road and the battery gauge is down to nine or 10 V because the glow plugs are continuing to suck power.
For no reason.

Sent from my iPhone using Tapatalk Pro

JohnT24 · Apr 25, 2017

Here's another thought

What about an interruption switch on the small terminal that goes to the keyswitch power
On the relay

Sent from my iPhone using Tapatalk Pro

Bugman · Apr 25, 2017

The WTS light is just a idiot light that comes on and has nothing to do with the glow plugs. You could pull all the glow plug wiring and relay and throw them in the trash and the WTS light will still come on. It is activated by the PCM.

A simple on/off switch wired in line with either control wire to the relay would also work for you.

Bugman · Apr 25, 2017

To add a little, if you want to interrupt the wiring to the glow plugs themselves you will need a switch that is capable of handling up to 200 amps DC.

Zmann · Apr 25, 2017

great Idea IMO

I was just thinking about this for My 6.0
but I am sure I would throw a load of glow plug codes and CEL every time I shut them off manually

the later strategy 6.0 trucks throw the CEL because the Glowplugs are considered an emissions
related item you 7.3 guys don't have to deal with that AFAIK

keep up on this mod
I think it's a waste to fire up the GP's for so long

Bugman · Apr 25, 2017

I really don't see any reason to disable them.

Years ago when owners first started putting switches on the relay they would say that it would extend the life of the relay and plugs. I found that the factory relay was the weak link in the system and corrected it. I am going on over 17 years on my Stancor with zero problems. I tested my glow plugs last fall and they are all still good with close to 200,000 miles on them. And I bought a bunch of them when Autozone was selling them for less than a buck. Some I have given away and some I have sold over the years as I found out that I didn't need a lifetime supply of them

I also don't see where it is a waste to fire them up for so long. At the most all they are costing you is very little in fuel over the life of the truck.

As I mentioned if you want to shut them off then all you need is a simple on/off switch placed in line with either the hot side of the relay or if you really want to control them yourself then with the PCM side that provides the ground for the relay.

JohnT24 · Apr 25, 2017

Bugman said:
if you want to shut them off then all you need is a simple on/off switch placed in line with either the hot side of the relay or if you really want to control them yourself then with the PCM side that provides the ground for the relay.

yep
Thats what I did. works good.

It's the hot from the key switch, so it's just like you turned the key switch off.

no juice to the relay/ and no juice to the glow plugs.

exactly what I wanted.

volt gauge pops right back up to normal as soon as I flip the switch.

a nice little theft deterrent also.

thanks. :thumbup:

old man dave · Apr 29, 2017

JohnT24 said:
Thanks.

Why?

Only because I have the cable/switch handy.

Ive read about the carbon
I still think its excessive time to be on.

Sent from my iPhone using Tapatalk Pro

Ever wonder why some people have a hell of a time pulling old glowplugs? Its the carbon buildup! Try pulling a stuck one that breaks off and you will regret ever thinking about not using the stock glowplug control especially if you wind having to pull the head.

Here's a reference for the White-Rodgers (stancor) HD relay:

http://www.dieselorings.com/16-009-white-rodgers-stancor-586-902-monster-glow-plug-relay.html

The much cheaper but just as good is the Western Plow 56131 snow plow relay. If you google it you can find them for $15-20. Other brands will show up but the Western is the brand to get.