GPR LED Light Mod Question
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GPR LED Light Mod Question
I found this site today and decided to sign up. I need some direction. I have a 2000 F250 SD 7.3 California Truck. The truck is having hard starts and I decided to change out glow plugs and install the LED Light Mod. The glow plugs were changed without issue but I have a question or two regarding the LED light. The LED installation went well but I seem to not have power thru the relay. I have 12v to one side of the relay but when I turn the key to KOEO there is no voltage to the other side of the relay. The relay doesn't click when power is applied. The two small wires on each side of the relay show power. I would think the relay is bad. This truck has the glow plug control module also. Where do I hook up the LED power wire, to the relay right? Could both the relay and control module be bad? If so, wouldn't an SES light trigger? Thanks in advance for any input.
Last edited by HollowayDoc; Jan 12, 2015 at 06:48 PM. Reason: spelling
Post Fiend
Joined: Mar 2007
Posts: 26,966
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From: Texas
Here's the picture I meant to post. It has a little more detail.
I've never hooked one up on a GPCM. You could either pull the hot lead for your light from any of the wires heading to a glow plug, or since those wires can trip a code if the readings are off, you can check for which wire is the ground signal.
I'm assuming the GPCM is activated by a ground signal from the PCM since it looks like they have battery voltage wired directly to the connectors.
I'd use a multi-meter and check the pk/o (should be pink wire with orange tracer) from PCM pin 101 to see if it gives a ground signal when the key is first turned on. If that doesn't work, check the w/lg (white / light green) wire from PCM pin 8. The Vref should be a 5 volt reference signal and the battery voltage should be your 12v from the battery.
If you can find the ground signal, hook up the LED to a fused 12v power source and then hook the other lead to the wire you find that sends the ground signal.
I've never hooked one up on a GPCM. You could either pull the hot lead for your light from any of the wires heading to a glow plug, or since those wires can trip a code if the readings are off, you can check for which wire is the ground signal.
I'm assuming the GPCM is activated by a ground signal from the PCM since it looks like they have battery voltage wired directly to the connectors.
I'd use a multi-meter and check the pk/o (should be pink wire with orange tracer) from PCM pin 101 to see if it gives a ground signal when the key is first turned on. If that doesn't work, check the w/lg (white / light green) wire from PCM pin 8. The Vref should be a 5 volt reference signal and the battery voltage should be your 12v from the battery.
If you can find the ground signal, hook up the LED to a fused 12v power source and then hook the other lead to the wire you find that sends the ground signal.
Lead Driver
Joined: Sep 2010
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Hotshot
Joined: Jan 2011
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From: Puget Sound
I was intrigued, so I'm jumping in. Pin 41 on the 42-pin connector is common from the PCM, and pin 13 is the GP control signal. I don't advocate tapping into a control signal from the PCM (impedance change may bugger up the circuit). No matter what you do, you're tapping into a wire to get your signal - this is opposed to the easy task of putting a pair of connectors on a GPR.
The best I can suggest is to tap into one glowplug wire for your hot signal (pardon the pun) to the LED, and ground the other end of the LED in the cab. This will tell you when that single glowplug is active, and the wiring is setup up so that they are all on at the same time.
Tying into a GP wire is a little tricky - those cheap crimp splices would introduce corrosion and eventual failure with this current and environment. This is a strip, solder, and seal task.
The best I can suggest is to tap into one glowplug wire for your hot signal (pardon the pun) to the LED, and ground the other end of the LED in the cab. This will tell you when that single glowplug is active, and the wiring is setup up so that they are all on at the same time.
Tying into a GP wire is a little tricky - those cheap crimp splices would introduce corrosion and eventual failure with this current and environment. This is a strip, solder, and seal task.
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Post Fiend
Joined: Mar 2007
Posts: 26,966
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From: Texas
...
The best I can suggest is to tap into one glowplug wire for your hot signal (pardon the pun) to the LED, and ground the other end of the LED in the cab. This will tell you when that single glowplug is active, and the wiring is setup up so that they are all on at the same time.
The best I can suggest is to tap into one glowplug wire for your hot signal (pardon the pun) to the LED, and ground the other end of the LED in the cab. This will tell you when that single glowplug is active, and the wiring is setup up so that they are all on at the same time.
This comes with the qualification that I actually have no friggin idea what the correct answer is. Tapping into a hot wire would be the easiest method.
I guess if you go that route first and get a CEL, then you can always switch to plan B.
Lead Driver
Joined: Jun 2004
Posts: 6,315
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From: Amarillo, TEXAS!
I guess since nobody else has asked, I will. Given the fact that a malfunction in the glow plug system on a truck with a control module will set a DTC and MIL, why bother with an indicator light?
Post Fiend
Joined: Mar 2007
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From: Texas
The glow plug codes are OBDII codes, so the auto parts stores or cheap readers (since CA won't allow a parts store to read codes for free) can read them.
Hotshot
Joined: Jan 2011
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From: Puget Sound
The GPCM does have diagnostics, so the LED mod could very well be superfluous.
Hotshot
Joined: Nov 2006
Posts: 11,286
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From: North of Greenville
... and quite a while back, in another of the longer GPR LED status indicator threads, someone tossed out the possibility of using a 10-segment LED bar graph indicator and tapping into each of the 8 GP power wires so that you could see if any individual GP lost its input from the GPCM, and even know which one it is!