Glow plug relay
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Freshman User
Joined: Mar 2008
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Glow plug relay
Quick question. 2001 F-250 7.3L
My truck doesnt like to start on cold mornings when I forget to plug it in. I had the glow plugs replaced a couple months ago and I have no voltage meter to test the relay. I put my test light on it and I have one constant power pole and another that gets power when the key comes on. Can the relay still be bad even though its sending power through and I hear an audible click from it when the relay goes on and off???
And out of curiosity, whats the second taller relay for that sits right next to it??
Thx guys
My truck doesnt like to start on cold mornings when I forget to plug it in. I had the glow plugs replaced a couple months ago and I have no voltage meter to test the relay. I put my test light on it and I have one constant power pole and another that gets power when the key comes on. Can the relay still be bad even though its sending power through and I hear an audible click from it when the relay goes on and off???
And out of curiosity, whats the second taller relay for that sits right next to it??
Thx guys
Post Fiend
Joined: Mar 2007
Posts: 26,966
Likes: 50
From: Texas
The test light will do the same thing as a volt meter. If you have power at the second post immediately after the key is turned on it sounds like your GPR is working. The second relay is your IAH (Intake Air Heater) relay.
How hard is your truck to start on cold mornings? Keep in mind the wait to start light is not actually connected to the glow plugs. Maybe you can try leaving the key in the on position for 20 or 30 seconds before attempting to start. The glow plugs will stay on up to 2 minutes depending on conditions so you can wait a little bit after the light goes out before trying to start.
How hard is your truck to start on cold mornings? Keep in mind the wait to start light is not actually connected to the glow plugs. Maybe you can try leaving the key in the on position for 20 or 30 seconds before attempting to start. The glow plugs will stay on up to 2 minutes depending on conditions so you can wait a little bit after the light goes out before trying to start.
Smokin
Joined: Jun 2006
Posts: 8,849
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Quick question. 2001 F-250 7.3L
I put my test light on it and I have one constant power pole and another that gets power when the key comes on. Can the relay still be bad even though its sending power through and I hear an audible click from it when the relay goes on and off???
I put my test light on it and I have one constant power pole and another that gets power when the key comes on. Can the relay still be bad even though its sending power through and I hear an audible click from it when the relay goes on and off???
Elder User
Joined: Jun 2007
Posts: 853
Likes: 1
Not to be argumentative,I do agree the gpr SEEMS to be working properly.But some here have found that there would be a large voltage drop across the relay,Say about two volts.I believe its because internally the contacts on the GPR get all burnt up{someone had pics of it torn apart}And that greatly reduces the contact surface,so more resistance and less voltage.And that would make it not be enough for the glow plugs to burn hot.In order to test the GPR you really should use a multi meter.Even a pos will do the trick.
Welcome to the forum.
Welcome to the forum.
Hotshot
Joined: Jan 2008
Posts: 13,144
Likes: 11
From: Rochdale MA
Good call Bruce. I have seen motor starter contacts that have been toast. And you will get a voltage drop across the terminals.
You can get a cheap digital multi meter at Home Depot, Sears, or Lowes.
You can get a cheap digital multi meter at Home Depot, Sears, or Lowes.
Fleet Owner
Joined: Jun 2004
Posts: 25,090
Likes: 1,112
From: Rio Rico, AZ.
Two years ago I was stuck in a campsite at 7000 feet with a truck that would not start.
I swapped the AIH relay into the glow plug relay position and it's been doing fine like that ever since.
I swapped the AIH relay into the glow plug relay position and it's been doing fine like that ever since.
Posting Guru
Joined: Jul 2007
Posts: 1,730
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From: SE Wisco
Not to be argumentative,I do agree the gpr SEEMS to be working properly.But some here have found that there would be a large voltage drop across the relay,Say about two volts.I believe its because internally the contacts on the GPR get all burnt up{someone had pics of it torn apart}And that greatly reduces the contact surface,so more resistance and less voltage.And that would make it not be enough for the glow plugs to burn hot.In order to test the GPR you really should use a multi meter.Even a pos will do the trick.
Welcome to the forum.
Welcome to the forum.
Do the GPR mod (In my sig) and you will always know if power is going across the relay. It also works great to know if you REALLY need to wts, or if the light is lying.
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Posting Guru
Joined: Jul 2007
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From: SE Wisco
Not to be argumentative,I do agree the gpr SEEMS to be working properly.But some here have found that there would be a large voltage drop across the relay,Say about two volts.I believe its because internally the contacts on the GPR get all burnt up{someone had pics of it torn apart}And that greatly reduces the contact surface,so more resistance and less voltage.And that would make it not be enough for the glow plugs to burn hot.In order to test the GPR you really should use a multi meter.Even a pos will do the trick.
Welcome to the forum.
Welcome to the forum.
Try the GPR mod. I did a write up on it a while back.
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From: Farmington, Minnesota
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Freshman User
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thx for the replies all!!!
I will have to get a meter and check the voltage I guess. I was comparing the pictures in the how to mod and looking at mine and I have a red wire going from one small post and connected to the other small post?? anyone have any insight on that???
I will have to get a meter and check the voltage I guess. I was comparing the pictures in the how to mod and looking at mine and I have a red wire going from one small post and connected to the other small post?? anyone have any insight on that???
Laughing Gas
Joined: Jan 2007
Posts: 870
Likes: 9
From: Carbondale, CO
Cus Bus, not sure about the wiring on your truck. Mine was just as in Guzzles mod write up for the Stancor relay. I've tried to attach link to this. You should be able to jump across the two large posts with a large screwdriver for @ 30 seconds, then try to start.
Here's the URL for the link: Welcome to guzzle's Stancor GPR replacement Mod Web Page
DND58
Here's the URL for the link: Welcome to guzzle's Stancor GPR replacement Mod Web Page
DND58