78 crew cab electrical issue - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**ddc456** · 04-09-2018, 10:14 PM

Ugh where to start. Original wiring was fried by the prior owner, so I grabbed an original harness out of a 77 crew cab that wasn’t all cut up. Few different plugs, wiper motor, wiper switch, ac etc but for the most part it’s just about the same. Where my problem is the gauge pack from the 77 isn’t working, yes the gauge pack that was orignal to the harness, not the original one from the 78. The other problem is only about half the fuse block seems to be working. Harzards, wiper, brake lights and accessories, most of the others aren’t testing out.
Any ideas where to start trouble shooting guys?

Thanks
Doug
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**ddc456** · 04-13-2018, 11:09 AM

bump to all you wiring guys out there. Little help please.

ray_mcavoy · 04-13-2018, 03:30 PM

For the gauge pack, start by checking the "CLSTR FEED" fuse. Should be a 4 Amp fuse located near the bottom of the fuse block.

Some of the fuses in the fuse block receive constant battery power from a 12ga red wire (circuit #2B on the factory wiring diagram). Other fuses receive switched accessory power from the ignition switch (circuit #4), and others recieve switched ignition power (like that cluster feed fuse) from circuit #3. Most all of them lead back to the ignition switch so a poor connection there or a bad switch could be the problem.

Thanks to hatzie, you can download the factory wiring diagram here --> http://67-72chevytrucks.com/vboard/s...d.php?t=545416

04-09-2018, 10:14 PM	#1
ddc456 Active Member Join Date: Jan 2014 Location: Bend Oregon Posts: 163	78 crew cab electrical issue Ugh where to start. Original wiring was fried by the prior owner, so I grabbed an original harness out of a 77 crew cab that wasn’t all cut up. Few different plugs, wiper motor, wiper switch, ac etc but for the most part it’s just about the same. Where my problem is the gauge pack from the 77 isn’t working, yes the gauge pack that was orignal to the harness, not the original one from the 78. The other problem is only about half the fuse block seems to be working. Harzards, wiper, brake lights and accessories, most of the others aren’t testing out. Any ideas where to start trouble shooting guys? Thanks Doug Posted via Mobile Device

04-13-2018, 11:09 AM	#2
ddc456 Active Member Join Date: Jan 2014 Location: Bend Oregon Posts: 163	Re: 78 crew cab electrical issue bump to all you wiring guys out there. Little help please.

04-13-2018, 03:30 PM	#3
ray_mcavoy Registered User Join Date: Nov 2009 Location: Sherman, ME Posts: 2,358	Re: 78 crew cab electrical issue For the gauge pack, start by checking the "CLSTR FEED" fuse. Should be a 4 Amp fuse located near the bottom of the fuse block. Some of the fuses in the fuse block receive constant battery power from a 12ga red wire (circuit #2B on the factory wiring diagram). Other fuses receive switched accessory power from the ignition switch (circuit #4), and others recieve switched ignition power (like that cluster feed fuse) from circuit #3. Most all of them lead back to the ignition switch so a poor connection there or a bad switch could be the problem. Thanks to hatzie, you can download the factory wiring diagram here --> http://67-72chevytrucks.com/vboard/s...d.php?t=545416



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