GPR Circuit Issue(s) Discovered
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Hotshot
Joined: Nov 2006
Posts: 11,286
Likes: 263
From: North of Greenville
GPR Circuit Issue(s) Discovered
Duh... Is it plugged in? Is it turned on?
Those two questions are roots of the KISS approach to lots of troubleshooting, and this morning, it proved basic to the issue I've had this winter with having to keep my truck plugged in EVERY night (on a timer, truck would not start otherwise). I've just been lazily relying on my faithfulness to plug it in without chasing down the root issue.... until this morning when I realized I had forgotten to plug in last night and thought, "enough is enough"!
DVM to the rescue....
Results.... ZERO voltage going TO the GPR! So, I now know why I've had to plug in the truck every night, but I do not yet know the REAL WHY behind that why!
My plans include...
- tracing/testing the 12v hot supply line/connections
- tracing/testing other connecting wires on small posts
- clean up & secure battery connections (saw some corrosion this morning on a PS battery post)
- clean & tighten primary engine ground connections
Any other suggestions? Remember, though, I'm not a sparky or highly experienced electrical dude, though I do know how to use (sort of) my DVM and make solid, weathertight connections when working on wiring.
Those two questions are roots of the KISS approach to lots of troubleshooting, and this morning, it proved basic to the issue I've had this winter with having to keep my truck plugged in EVERY night (on a timer, truck would not start otherwise). I've just been lazily relying on my faithfulness to plug it in without chasing down the root issue.... until this morning when I realized I had forgotten to plug in last night and thought, "enough is enough"!
DVM to the rescue....
Results.... ZERO voltage going TO the GPR! So, I now know why I've had to plug in the truck every night, but I do not yet know the REAL WHY behind that why!
My plans include...
- tracing/testing the 12v hot supply line/connections
- tracing/testing other connecting wires on small posts
- clean up & secure battery connections (saw some corrosion this morning on a PS battery post)
- clean & tighten primary engine ground connections
Any other suggestions? Remember, though, I'm not a sparky or highly experienced electrical dude, though I do know how to use (sort of) my DVM and make solid, weathertight connections when working on wiring.
Fleet Mechanic
Joined: Jul 2005
Posts: 1,800
Likes: 52
From: Southern Colorado
Before you start, pull both battery neg. terminals so that you don't short something with a socket wrench. Even if a connection looks solid, either loosen and re-tighten, or take it apart anyway and buff the connection points with steel wool. Most electrical work is a matter of discipline, rather than skill, so study carefully, take your time, and use the DVM liberally until you find out what's going on.
I have installed (and you could temporarily install) an analog voltmeter under the dash. When I cycle the ignition, it drops below 11v, and this tells me that the glow plugs are working. A while ago, my GPR failed and my first indication (after the truck failed to start!) was high voltage showing when the ignition was cycled.
I have installed (and you could temporarily install) an analog voltmeter under the dash. When I cycle the ignition, it drops below 11v, and this tells me that the glow plugs are working. A while ago, my GPR failed and my first indication (after the truck failed to start!) was high voltage showing when the ignition was cycled.
Thread Starter
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Hotshot
Joined: Nov 2006
Posts: 11,286
Likes: 263
From: North of Greenville
Before you start, pull both battery neg. terminals so that you don't short something with a socket wrench. Even if a connection looks solid, either loosen and re-tighten, or take it apart anyway and buff the connection points with steel wool. Most electrical work is a matter of discipline, rather than skill, so study carefully, take your time, and use the DVM liberally until you find out what's going on.
I have installed (and you could temporarily install) an analog voltmeter under the dash. When I cycle the ignition, it drops below 11v, and this tells me that the glow plugs are working. A while ago, my GPR failed and my first indication (after the truck failed to start!) was high voltage showing when the ignition was cycled.
I have installed (and you could temporarily install) an analog voltmeter under the dash. When I cycle the ignition, it drops below 11v, and this tells me that the glow plugs are working. A while ago, my GPR failed and my first indication (after the truck failed to start!) was high voltage showing when the ignition was cycled.
Thanks for the tips and insights. You're recommendations are consistent with my "maturing" approach to virtually everything... take it slow, think through carefully, and "when in doubt - don't".
I have plans for the volt meter, and had decided against the LED signal light for the GPR, but now see sense in it again.
Logistics Pro
Joined: Aug 2009
Posts: 3,609
Likes: 324
From: Arizona
Just be aware that the trigger wire for the relay is a ground, and the PCM sends a ground signal through that wire to energize the relay which should already have power at the small + wire when the key is on. The reason I am telling you this is so you do not hook up 12 volts to that signal wire and possibly cause some damage. I don't have a picture of the relay handy but maybe someone will post one shortly. There should always be 12 volts at one of the big connections and with key on there should be 12 volts at the small + terminal. When the PCM sends the ground signal there should be 12 volts at both large wires due to the small + and small - closing the relay. If you have no 12 volts to one of the large wires I'd start there, that wire should always have power and shouldn't be too hard to follow. Hopefully when you checked for power you had a good ground, and did you test the meter first on the battery to make sure it is working and set correctly?
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Hotshot
Joined: Nov 2006
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From: North of Greenville
Did not check specifically on this one use, but this is the same meter I've used recently in the house on my 110/120 circuits with no issue. I can check it this evening once I get back home, but I do not suspect a problem with the meter.
One additional detail.... I could hear a fast but soft chatter style clicking inside the relay with the key on, even though no voltage was showing on the incoming post.
One additional detail.... I could hear a fast but soft chatter style clicking inside the relay with the key on, even though no voltage was showing on the incoming post.
Butt-Head
Joined: Apr 2004
Posts: 9,448
Likes: 2,934
From: Reed Point, MT
Lead Driver
Joined: Jul 2017
Posts: 6,855
Likes: 2,332
From: WV
No personal experience, but I’ve read on here that there’s a fusible link in the hot wire. I’d start by checking continuity of this wire, then move to find the fusible link if it shows a broken circuit.
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Hotshot
Joined: Nov 2006
Posts: 11,286
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From: North of Greenville
The GPR is not in the valley where it used to be. I moved it to the PS fender about 8 years ago. The chattery clicking is definitely from the GPR.
https://www.ford-trucks.com/g/album/2843812
Yes, that is part of my tracing strategy for the primary feed wire.
https://www.ford-trucks.com/g/album/2843812
Yes, that is part of my tracing strategy for the primary feed wire.
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Logistics Pro
Joined: Aug 2009
Posts: 3,609
Likes: 324
From: Arizona
If the GPR is chattering you have power there. After making sure the power and ground is solid try a new GPR.
Logistics Pro
Joined: Aug 2009
Posts: 3,609
Likes: 324
From: Arizona
It has to be getting power from somewhere, it can't chatter without power. It might not be enough power to latch it but it's got to be seeing something
Butt-Head
Joined: Apr 2004
Posts: 9,448
Likes: 2,934
From: Reed Point, MT
The GPR is not in the valley where it used to be. I moved it to the PS fender about 8 years ago. The chattery clicking is definitely from the GPR.
https://www.ford-trucks.com/g/album/2843812
https://www.ford-trucks.com/g/album/2843812
Thread Starter
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Hotshot
Joined: Nov 2006
Posts: 11,286
Likes: 263
From: North of Greenville
No issue. Didn't mean to sound terse. I moved it to open up the valley a bit, and it's been helpful on a couple of occasions for it to be where it is, out of the way.
Lead Driver
Joined: Sep 2010
Posts: 7,793
Likes: 50
My l99 Pete, I had to run a switched ground to activate the relay.....the 02 is still goin being activated by the pcm..(led along with Volt reading tells me)..i drop about 1v while it's cycling
btw...them solenoid injector shim kit we bought YEARS ago, may see use here soon on the l99...she crapped out on me back in Nov...mudfest was foind in tank and fuel bowl
btw...them solenoid injector shim kit we bought YEARS ago, may see use here soon on the l99...she crapped out on me back in Nov...mudfest was foind in tank and fuel bowl