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Discussion Starter #1
I have a problem with the in-cab PCM power feed fuse in my 1999 F550 S-D. I occasionally lose power to the PCM indicated by no "wait to start" light and either it won't start or it will randomly shut off going down the road. I can wiggle the fuse around (it feels loose) and it will fire back up until the next random incident. I'm fairly certain it is an issue inside the fuse block.
Short of replacing the entire fuse block and harness, how can I fix this?
I had one thought... If I knew the color coding of the wires in the fuse block harness, I'd be tempted to just tap into the harness and install an auxiliary fuse holder in the PCM feed circuit, effectively bypassing the problematic fuse block. However, I have been unable to find that info so far. Can anybody tell me which wires I need to tap?
Any help would be greatly appreciated.
 

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Take a small screw driver and try and bend the connectors back in. Also take some pliers and twist the prongs on the fuse some
 

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Discussion Starter #3
Thanks. I'll give that a shot. Seems like the plastic around that particular fuse has been melted somehow.
 

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I have a wire diagram at home, I'll look at it and give you the wire colors if you still need them after trying sbluke55 and bullgears ideas first

sent from jsbelectro
 

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Discussion Starter #5 (Edited)
I'm resurrecting this thread because the problem has been getting worse lately. I need a permanent fix. Tweaking the fuse prongs worked for a while but I have had numerous reoccurrences during the last couple of trips. I ended up having to strip back some copper wire and jam it in the fuse contacts along with the fuse to get it home last time.
So... does anybody have a "how to" on bypassing that fuse holder #30?
I need to figure out where to tap in to that circuit and install an external in-line fuse.
I found a wiring diagram and this is what I think I know so far;
  • fuse #30 feed is "hot in run or start"
  • coming out of fuse block thru Pin 34 (C243)
  • RED/LT GRN wire
  • goes through "S179" ( assuming that is a splice)
  • feeds "PCM Diode"
One thing confusing me is my diagram shows fuse #30 in two different places (one feeding the PCM diode and another feeding the fuel heater and waste gate solenoid) but it doesn't show them connected. Maybe there are two RED/LT GRN wires coming off Pin 34 C243. I'm thinking it may be WAY easier to tap into the under hood power distribution block at the PCM diode than it would be to get to the wires under the dash. If so, where can I pick up a close-by "hot in run/start" feed that is capable of powering that circuit?
 

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Discussion Starter #6
Nevermind... fixed it.
Sure wish I had found out a LONG time ago that the fusebox contacts are easily replaceable!!!
After pulling the whole fusebox, I discovered that the front of the box just snaps right off (after all the fuses/relays are pulled) and then the individual contacts will just pop right in/out. I pulled the offending the contacts out, rebent them best as I could, swapped them into a non-critical circuit, and put good contacts into the fuse #30 spot.
 
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