HELP! Truck is Haunted (Parasitic Drain) - Ford Powerstroke Diesel Forum
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post #1 of 16 Old 04-28-2018, 06:51 AM Thread Starter
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HELP! Truck is Haunted (Parasitic Drain)

Been chasing this problem for a while now and it's been getting worse with time. It happened once over the winter, then started once a week, now it's every few minutes to the point where the truck is now dead in a Chinese food parking lot waiting for a rescue attempt.

Symptoms: The dome and cargo light will come on and off randomly - sometimes steady on, sometimes flickering. The switch by the headlight knob is off. The blower motor is also seeing rapidly alternating voltage such that it is trying to engage many times per second but isn't enough for it to actually run. This occurs even with the dome light relay removed (Relay 1 - see below) except the dome light doesn't come on.

What I've tried: It's been hard to trace due to the intermittent nature of it. I also work out of town and leave the truck at my parents house so they have just been disconnecting the batteries when they see it - naturally when I get home it doesn't do it. When it's not visibly occurring, there is no parasitic drain observed on a multimeter. I thought I found the culprit at the #1 relay - a copper winding had broke loose and was touching the always hot lead so I thought it was enough to intermittently energize the coil and close the relay. I nearly cried when the symptoms occurred again with the relay completely removed. Last night was the first time it happened while I was in the truck and I tracked the clicking noise to the blower motor connector. The big 2 wire connector on the passenger fender was somehow making a ticking noise that was muffled when I held the connector. I unplugged it but the lights continued to flicker.


Since the blower motor and dome lights are on 2 separate circuits, I'm at a bit of a loss as to what the issue might be. PCM related? It had a TS6 chip in it that I had reburned and it will no longer run with the chip. It could be a bad burn, but I imagine that's rare. The chip has been unplugged for all of this. The truck sat for about a year while I rebuilt it so I don't remember the timeline of whether the chip was in or out when it first started. It's also been throwing an intermittent KAM code with a CEL but it could be because I keep disconnecting the batteries.

So, any thoughts? I've been dealing with this for months and is making me question my love of taking care of old, used trucks. I was seriously debating buying a new Tundra last night....

Edit: 2000 7.3 XL - not the one in the signature

2000 ECLB 4x4 7.3L PSD - Converted from a beat up XL farm truck and frame off restored thanks to New England road salt
Cosmetic: 05 Harley front end, 11 tailgate, black sport full power interior, 05 dash with aux switches and brake controller
Performance: AFE intake, SPX billet compressor wheel, Turbomaster wastegate, blank pedestal & exhaust housing, MBRP 5" exhaust, PHP Hydra, gauges and CTS2
Audio: Sony XAV-AX5000, JBL Club speakers, fully sound deadened

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post #2 of 16 Old 04-28-2018, 07:10 AM
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Dome lights - thatís not pcm issue. IF you replace the accessory relay and it still doesnít turn off as should, itís the cluster. Fix? Replace the instrument cluster. Warning: IIRC, it should be the accessory relay.

Cheap fix? Rewire that relay to your ignition. Way back, windows and radio not working or turning on or turned on when it wanted to. Got tired and rewired it to ignition. Windows work, radio worked .


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post #3 of 16 Old 04-28-2018, 08:26 AM
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I can't deduce that these two maladies are related. Perhaps they are, but I would diagnose them separately.

With the relay completely removed there is no power applied to the blk/blu wire (which is the dome light circuit). Remember, Ford dome light circuits apply B+ to the bulb, and the other side of the bulb is to chassis ground. So somehow B+ is being introduced into the blk/blu wire. My guess is an old alarm system that had dome light supervision, or the underdash fuse box has a bad trace or internal corrosion. Another possibility would be one of the over head dome / map assemblies: There is B+ power at all times for the map lights. (lt grn / yel wire). If this were to get shorted to the blu/blk internally in one of the fixtures, the dome light circuit would be powered. There is a separate fuse for the map / underhood / glove box lights. Pull it too, and see if the dome light problem stays / goes away.

The Blower: There is a relay in the under hood fuse center. This relay supplies power to one side of the blower motor. The other side is grounded through the fan switch, via the resistor network to get the different speeds. Identify this relay. Try running the truck without the relay installed, and evaluate what the blower does without it. Also, if you can catch the blower acting up, touch / listen to the relay and see if it is chattering. If = yes, my guess is the coil of the relay is not being grounded properly. I don't know where the under hood grounds are. The power for the relay is supplied through a fuse in the under dash fuse box, which comes from the IGN switch. A jankey IGN switch contact (there are 5 sets of contacts, only one of which affects the running of the engine) could perhaps cause the blower problem, but couldn't be related to the dome lights with the relay removed.

There's some ideas.

Last edited by DaveP.; 04-28-2018 at 08:32 AM.
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post #4 of 16 Old 04-28-2018, 09:48 AM
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Because this is a 2000, you have a GEM module that is located on the backside of your in-cab fusebox. There is a common issue where a leak in the corner of the windshield gasket causes water to drip right into the GEM.

Anytime people talk about multiple issues that "haunt" them the first thing to do is to drop the fusebox (easy 4 screws) and have a look at your GEM for signs of wetness or corrosion.
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post #5 of 16 Old 04-28-2018, 10:30 AM Thread Starter
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Thanks to both of you for the help. My factory shop wiring manuals just arrived today which may may it easier to trace.

DaveP. good use of vocab! Also, you are spot on in your wiring colors. The truck did have an aftermarket keyless entry system installed so I will check that. It's all been removed but the wire taps remain in place. I think you're right with a fixture short as there is no where that provides power to the lights after the relay. Seeing these diagrams is very helpful because it helps isolate what it is NOT.

I'm still convinced the two are related because they only occur at the same time, but the diagrams don't really show anything that would tie them together.

2000 ECLB 4x4 7.3L PSD - Converted from a beat up XL farm truck and frame off restored thanks to New England road salt
Cosmetic: 05 Harley front end, 11 tailgate, black sport full power interior, 05 dash with aux switches and brake controller
Performance: AFE intake, SPX billet compressor wheel, Turbomaster wastegate, blank pedestal & exhaust housing, MBRP 5" exhaust, PHP Hydra, gauges and CTS2
Audio: Sony XAV-AX5000, JBL Club speakers, fully sound deadened

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post #6 of 16 Old 04-28-2018, 01:10 PM Thread Starter
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Update: Because I know everyone is on the edge of their seat, the lamps are being fed by the airbag circuit - when fuse 2 (airbags) is removed, the lights go out. Removing the map light fuse has no effect. Also, the noise I was hearing was the blower motor itself running on low, no relay clicking. This, however, remains on even when the airbag fuse is removed so it's being fed elsewhere.

Next step is to check the GEM.

2000 ECLB 4x4 7.3L PSD - Converted from a beat up XL farm truck and frame off restored thanks to New England road salt
Cosmetic: 05 Harley front end, 11 tailgate, black sport full power interior, 05 dash with aux switches and brake controller
Performance: AFE intake, SPX billet compressor wheel, Turbomaster wastegate, blank pedestal & exhaust housing, MBRP 5" exhaust, PHP Hydra, gauges and CTS2
Audio: Sony XAV-AX5000, JBL Club speakers, fully sound deadened

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post #7 of 16 Old 04-28-2018, 01:12 PM
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The lamps as in head lights? Iím taking notes while trying to help


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post #8 of 16 Old 04-28-2018, 03:34 PM
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IF the installer used T-taps to interface to the ignition switch wires (or any wires for that matter) remove the t-tap and check the wire strands very carefully for having been cut by the t-tap. I've seen many, many conductors that were almost completely cut through by t-taps. Fixing this damage may not be associated with curing the issues with the dome lights and blower, but it needs to be fixed to restore integrity to the wires affected. The IGN wire would account for the trouble with the blower, but not with the dome lights.

There should be NO association between the Airbag fuse and the dome lights. The GEM does not have anything to do with the blower. BUT all these traces are internal in the fusebox / relay center, with the GEM on the back. I would suggest removing the four bolts that secure the fuse box to the IP frame and inspect for any pinched, damaged, or t-tapped wires. Access to inspect the wiring associated with the fuse / relay panel is greatly improved by getting it loose and pulled down. I've never torn one of these open, but I believe there are a bunch of traces and conductors held in a plastic matrix. Corrosion or even an overload that melted the plastic might cause an unintended short between circuits such as airbag and domelight control from the relay.

Some further ideas............

"DaveP. good use of vocab!"
You must be referring to my use of the word "Jankey". One of my favorite non-words. Glad you liked it.
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post #9 of 16 Old 04-28-2018, 06:01 PM Thread Starter
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Quote:
Originally Posted by DieselDC View Post
The lamps as in head lights? Iím taking notes while trying to help
Lamps as in dome and cargo lamp. Saturday is no day for note taking!

Quote:
Originally Posted by DaveP. View Post
You must be referring to my use of the word "Jankey". One of my favorite non-words. Glad you liked it.
I was actually referring to malady but props for that one too!

I removed the fuse box and GEM to find....corrosion! The GEM had some kind of acidic dust accumulated on the back side near the "vent" slots. This ate away at the green PCB material exposing the conductive under-layer and connecting some of the contacts. The fuse box itself showed signs of standing water in the form of green buildup. I was unable to separate the layers of the fuse box but could see internal corrosion as well. $200 later, eBay has replacements in the mail so hopefully this is the issue. Going to have to travel behind some dump trucks until I need a new windshield from the insurance co....

2000 ECLB 4x4 7.3L PSD - Converted from a beat up XL farm truck and frame off restored thanks to New England road salt
Cosmetic: 05 Harley front end, 11 tailgate, black sport full power interior, 05 dash with aux switches and brake controller
Performance: AFE intake, SPX billet compressor wheel, Turbomaster wastegate, blank pedestal & exhaust housing, MBRP 5" exhaust, PHP Hydra, gauges and CTS2
Audio: Sony XAV-AX5000, JBL Club speakers, fully sound deadened

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post #10 of 16 Old 04-28-2018, 06:27 PM
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Quote:
Originally Posted by Lt.Dan View Post
Lamps as in dome and cargo lamp. Saturday is no day for note taking!





I was actually referring to malady but props for that one too!



I removed the fuse box and GEM to find....corrosion! The GEM had some kind of acidic dust accumulated on the back side near the "vent" slots. This ate away at the green PCB material exposing the conductive under-layer and connecting some of the contacts. The fuse box itself showed signs of standing water in the form of green buildup. I was unable to separate the layers of the fuse box but could see internal corrosion as well. $200 later, eBay has replacements in the mail so hopefully this is the issue. Going to have to travel behind some dump trucks until I need a new windshield from the insurance co....


I donít know why hour trucks are so prone to windshield leaks.... Iíve have four 7.3 and each had leaked at the driver side. Kinda tire of the bs. None of my Toyotaís have leaked at all. Diesel power hungry problems.


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