Power only comes on intermittently

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melueloff

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Location
Windsor
First Name
Matthew
Truck Year
1988
Truck Model
v1500
Engine Size
5.7
I’ve been through most everything I can find on this problem, but mine seems to have a twist no one else has reported. Beast has run just fine off and on over about the last five years I’ve used him until now. Has been in pretty much constant service for the last two years. Sorry, it’s kinda long but I’m trying to be thorough.

About three weeks ago we went up into the mountains to put our trailer in storage for the winter. Did just fine until I dropped the trailer, pulled forward and turned him off. Went to start up again and it wouldn’t do anything. Power went out on the dash, little puff of electrical smoke up from the drivers engine side of the firewall somewhere. Tried the only thing I knew and tapped on the starter. Yes I know you’re not supposed to do that. Another time or two trying to start nothing happening and another puff or two of electrical smoke up on the drivers engine side of the firewall again, more tapping and he fired right up. Got back down into town, he worked for another two or three days and did it again. Tapped on the starter, he would start. Now, nothing. I turn the key, get the CEL and seatbelt light sometimes. Turn the key, dead. I pulled the starter and benched tested it, it’s fine. The battery just sitting is reading 12.3 V. I tried jumping the neg battery to a spot on the alternator to ground, nothing. I’ve checked the fuse links, they’re good. I’ve replaced the ignition module and that hasn’t helped. And I’ve put hands on every inch of wire I can.

But now, I found something different from everybody else. Turning the key may or may not light up the CEL and seatbelt light, but when it does there’s a relay click under the dash. It’s not outside in the engine compartment and it’s not the starter solenoid, but I can’t figure out what it is or where it is. I’ve been trying to find if there’s a relay that could be bad but I read electrical diagrams about as well as I read Greek. And the dash lights will come on, with the relay click on their own and go off on their own.

Laugh, point, laugh And point. It’s all good lol
 

75gmck25

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Northern Virginia
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Bruce
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1975
Truck Model
K25 Camper Special TH350 NP203
Engine Size
5.7
Your truck is much newer than mine, but in my truck it would be the fusible link that comes straight down from the power junction next to the brake booster. This 10 gauge wire with 14 gauge fusible link is what powers the dash and the HEI. If it has too much current it will start to burn through inside (the puff of smoke), but may keep enough integrity to power the dash. Usually it only takes a couple of “incidents” to burn through completely.

My fusible link started to fry/smoke when I installed battery cables backwards, but then worked fine later on. I didn’t realize how much it been weakened. Later on I was driving on the highway and turned on the headlights. The extra power draw and the extra amps burned completely through the link and I suddenly came to a stop on the highway. I spliced it temporarily, and then later replaced the link with a 14 gauge GM fusible link I bought at the parts store.
 

melueloff

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Oct 10, 2023
Posts
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Location
Windsor
First Name
Matthew
Truck Year
1988
Truck Model
v1500
Engine Size
5.7
75gmck25, I’ll go back and check those out again. I did continuity but not voltage. Maybe I’ll just replace all three of them to be on the safe side.
 

melueloff

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Posts
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Location
Windsor
First Name
Matthew
Truck Year
1988
Truck Model
v1500
Engine Size
5.7
We’ll, hours later, busted knuckles, more swearing than a battalion of Marines, and a sunburned leg, I went back to square one. Burnt out fusible. I had cut into it above where the wire itself had blown out. Replaced it more or less correctly and darn thing fired right up. Occam's Razor, “the simplest solution is almost always the best.” LOL
 

Scott91370

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Burleson, Tx
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Scott
Truck Year
1985
Truck Model
Sierra1500
Engine Size
350
Is there not a "real fix" to these fusable links that won't burn the truck to the ground?

I've been lucky and haven't had any issues (I should not have said that!!!) but so many do. And from what I understand you can't just put a regular fuse in its place.
 

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