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F650 blowing "Allison Transmission" fuse help

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Posted (edited)

2007 F650, 5.9 Cummins with an Allison trans with about 40,000 original miles. No prior symptoms. Today loaded double to go off island, shut truck off at ferry landing, went to re start to get on ferry & no crank, no signal to fender well mounted starter solenoid. Jumped starter solenoid & truck started but Service Engine light on & the transmission was in limp mode. Trace no crank & trans limp mode to blown 15 amp #30 "Allison Transmission" fuse blown in under dash fuse box, install new fuse, it blows as soon as key is turned to run position. I unplugged all modules (ABS, TCM, etc...) still blows fuse. Followed wiring harness closely from TCM forward to look for chaffing, found nothing & was confirming fuse was still blowing as I worked my way forward. I unclipped the harness at the fuel filter to confirm no chaffing/bare wires & then the fuse stopped blowing, nothing found. Re secured everything & it's been starting & operating normally again. Anyone have a similar  experience & give me a place to look as I have not been able to duplicate the symptom again & did not find a smoking gun. Thank you.

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Edited by Orcas Tow

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Possible the wiring harness going into the trans may be failing. Our old 07 650 with the 5.9/allison the harness went a few times and we had a allison dealer replace it. Did the same thing limp more, died while driving, would not start from time to time.

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It appears that you isolated the issue to the general area. The harness possibly has an internal failure within the confines of the harness outer sheathing. Do you have a good color coded wiring diagram available for the particular circuit? Possible that someone prior poked or probed something and caused a weak spot. I would hate to see one spend that coin for a harness. Give that harness and particular circuit a good quadruple check. You already have isolated a general area.

I think you are probably closer than you think.

You definitely live in God's country!

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Thanks, I agree. I will be finding this intermittent short. I have all I need to tear into & repair a wiring issue in the truck also a "short finder" hooked inline with the fused circuit today & have a 8 hour trip. The short finder beeps & has an internal re setting circuit breaker in the diagnostic tool to alert you when the load on that circuit changes/shorts. Im hoping it will rear its head today as I am the driver today but its mostly driven by my other guys for off island trips. 

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Posted (edited)

No symptom over 8 hours of driving. Its almost like Ford is taunting me by the picture in the Ford manual, like they know right where that little prick of a wire is protruding into a neighboring wire in the 150 wire harness, see figure 2, Grrrrr

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Edited by Orcas Tow

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I have my full faith that you will figure it out! I get really scared when someone else is doing electrical work to anything I own. When it is your own equipment, you exercise far more due diligence. Ford does a fairly decent job of putting together written material for wiring diagrams. Let us know what the issue was when you conquer the issue!

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Years ago we had the same issue with a 2006 f650 CAT/ allision.   Towed to Ford, they said it was an Allison issue.  Towed to Allison, they found an issue with the FORD wiring harness was pinched at the cab.  They cut out a 1 inch section of a wire and repaired it.  Never an issue after.   I think it was a green wire in the area of the cab/firewall.   I know we had a CAT, but it sounds like the exact issue, although ours stayed in limp mode.

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Thanks, Im into it today, have about of 5 feet of the harness spread open at this point for inspection starting at the firewall plug heading over the engine & then back towards the interface module & trans module at the rear of the cab. My wire is a white with orange tracer, nothing yet but still digging. 

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I had a 2007 F650 multiple issues. It had actually gotten to the point where it would shutdown and restart going down the road. As a last resort we replaced the whole wiring harness which solved the problem. Zip ties wore through in several spots.

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If one can find the problem circuit the individual circuit can be repaired. Wiring harness costs thousands of dollars to replace.

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To follow up I never have been able to duplicate the symptom after tanks of fuel run through it & my diagnostic testers hooked up so I ended up running a single new wire outside the harness back to the Trans module clipping the factory white/orange tracer wire at each end. With no symptom present at this time I think its the best solution.

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That is how the dealerships do it under warranty brother. Let us know how it works out! I think the call it a lay over. If they have to dig into the harness it is at the owners expense.

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