bp17oang Posted March 17, 2021 Author Share Posted March 17, 2021 Sounds like the fusible link on the main cab power wire, the large yellow wire, is bad It's hot up to the black box unit on the driver's side firewall. That's as far as I had patience to test at the time 🙄 Link to comment Share on other sites More sharing options...
kramttocs Posted March 17, 2021 Share Posted March 17, 2021 It's hot up to the black box unit on the driver's side firewall. That's as far as I had patience to test at the time 🙄 Black box unit? There is generally a junction post there but can't think of a black box. Photo? Link to comment Share on other sites More sharing options...
bp17oang Posted March 17, 2021 Author Share Posted March 17, 2021 Black box unit? There is generally a junction post there but can't think of a black box. Photo? It's some type of fuse block. There is a junction block on my 86. The 85 doesn't so I'm trying to sort out what that yellow wire plugged into on the 85??? Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted March 17, 2021 Share Posted March 17, 2021 Black box unit? There is generally a junction post there but can't think of a black box. Photo? Yeah, I'm not certain "black box unit" But I don't have a chassis cab either.. If you look at the EVTM for '86 you'll see how it splices to the ignition switch and the fuse panel for the circuits (like lights and brakes) that are on all the time. Link to comment Share on other sites More sharing options...
bp17oang Posted March 17, 2021 Author Share Posted March 17, 2021 Yeah, I'm not certain "black box unit" But I don't have a chassis cab either.. If you look at the EVTM for '86 you'll see how it splices to the ignition switch and the fuse panel for the circuits (like lights and brakes) that are on all the time. Both trucks have it. There's a black plastic housing mounted on the firewall with two phillips head screws. The yellow wire from the solenoid goes into a plug that connects to what I'm assuming is a relay that snaps up underneath that plastic housing Link to comment Share on other sites More sharing options...
kramttocs Posted March 18, 2021 Share Posted March 18, 2021 Both trucks have it. There's a black plastic housing mounted on the firewall with two phillips head screws. The yellow wire from the solenoid goes into a plug that connects to what I'm assuming is a relay that snaps up underneath that plastic housing Gotcha. Sounds like what the fuel pump relay snaps into. A black plastic hood piece that holds two relays. There is a yellow wire in that area that is the same as the cab yellow wire Jim is talking about on the passenger side that feeds the cab. It starts with the fuse link on the FMR (fender mounted relay), goes through the firewall on the passenger side and then splits into a few circuits. One branch goes through the firewall on the driver side and is hooked to the junction block or the aux battery relay if so equipped. The fuel pump relay is powered by a fuse link on the fmr but other relays like trailer and aux lighting have fuse links on the junction block or aux solenoid. That's factory though so yours could very well be using the yellow circuit direct to the relay. Can you test any of the Hot At All Times spots in the fuse box? Link to comment Share on other sites More sharing options...
bp17oang Posted March 25, 2021 Author Share Posted March 25, 2021 Gotcha. Sounds like what the fuel pump relay snaps into. A black plastic hood piece that holds two relays. There is a yellow wire in that area that is the same as the cab yellow wire Jim is talking about on the passenger side that feeds the cab. It starts with the fuse link on the FMR (fender mounted relay), goes through the firewall on the passenger side and then splits into a few circuits. One branch goes through the firewall on the driver side and is hooked to the junction block or the aux battery relay if so equipped. The fuel pump relay is powered by a fuse link on the fmr but other relays like trailer and aux lighting have fuse links on the junction block or aux solenoid. That's factory though so yours could very well be using the yellow circuit direct to the relay. Can you test any of the Hot At All Times spots in the fuse box? Been busy the last couple of weeks so I haven't had much time to fiddle around with anything Although, I have located my driveshafts. The rear one was actually a touch harder to acquire mainly because no one wanted to ship. Found one in Michigan close to a friend's house so he picked it up. Then a found a front at a junkyard in PA that was willing to ship for a reasonable fee. So, fingers crossed those will help me getting power to my wheels Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted March 25, 2021 Share Posted March 25, 2021 Been busy the last couple of weeks so I haven't had much time to fiddle around with anything Although, I have located my driveshafts. The rear one was actually a touch harder to acquire mainly because no one wanted to ship. Found one in Michigan close to a friend's house so he picked it up. Then a found a front at a junkyard in PA that was willing to ship for a reasonable fee. So, fingers crossed those will help me getting power to my wheels That still sounds like progress, and Progress is good!. Link to comment Share on other sites More sharing options...
bp17oang Posted March 25, 2021 Author Share Posted March 25, 2021 That still sounds like progress, and Progress is good!. Good perspective 👍 Sometimes tracking stuff down can be more frustrating than working on wiring! Link to comment Share on other sites More sharing options...
bp17oang Posted March 30, 2021 Author Share Posted March 30, 2021 Good perspective 👍 Sometimes tracking stuff down can be more frustrating than working on wiring! Well these drive shafts seem to be quite the debacle... The source I had on the front one just called me and said it's damaged. Figures. Just got my rear one and crawled under the truck and held it into place and it seems like it's too long. It also does not include the male slip yoke/stub shaft which I obviously need. Any spicer numbers for that section would be greatly appreciated Link to comment Share on other sites More sharing options...
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