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Radio clock staying on at Key Off -- 1997 Chevy K1500 5.7

  • Brocktoon
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26 Aug 2019 17:15 #33151 by Brocktoon
For about the last 2 weeks, I've been having trouble trying to figure out why the radio clock display has suddenly switched to on at all times. Earlier this month, I put a new pitman arm onto the truck to pass PA inspection. Since then, the clock shows on even at key off. At first I thought I might have pinched a wiring harness that runs along the front crossmember when I was wrestling with the pitman arm and steering box, causing a grounding issue, but there are only two wires there, which power the right side headlights, and they looked fine. The only way I've been able to turn the clock off is the pull the radio memory fuse, a 10 amp in slot #19. If I don't, it quickly drains the battery, which is over 5 years old and on it's last legs anyway. I have a shop manual for the truck, but the wiring diagrams aren't really helping me figure out what's wrong. Doesn't help that I'm not real smart and lousy at diagnosing anything.

Maybe related or maybe not, but the power side mirrors only move up and down on the drivers side, and -- if I remember -- left and down on the passenger side. The mirrors are tied to fuse #3 (Courtesy), and the fuse has blown a few times if I run everything tied to it. I've replaced the left door jamb switch, which I broke when took the door off to put on a new rocker panel earlier in the summer.

I probably haven't explained it very well, but I just can't figure it out. I know newer trucks have a RAP relay that keeps the radio on until you open the door, but I'm pretty sure older GM trucks (88-98) don't. It didn't do this before, and I know it's about time for a new battery, but the last thing I want is to have a new one get drained also.

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29 Aug 2019 13:23 #33264 by Brocktoon
Just a quick update with a little more info:

I took the truck out for a bit yesterday, and had the A/C and recirc buttons on. I noticed that the lights for those buttons would both shut off at various times for a few seconds, and then come back on. It didn't seem to happen at any particular time like driving over bumps, at least as far as I could tell. So maybe it could be a grounding issue or a short in a grey wire that the shop manual says is circuit 8?

I understand it's not the end of the world, the truck still drives, I just can't seem to let things like this go until I figure out what's wrong with it. If anyone has any ideas, I'd really appreciate it. Thanks.

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29 Aug 2019 15:38 #33271 by jreardon

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The only way I've been able to turn the clock off is the pull the radio memory fuse, a 10 amp in slot #19.


There is another fuse, Fuse 17 10A that is ignition switch fed that's only hot in accessory or run position. I would make sure both side of that fuse is not hot when the key is out of ignition.
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30 Aug 2019 19:57 #33305 by Brocktoon
I did a quick voltage check on fuse 17, between the fuse and IP ground 200.

Key out - 48 mV
Acc - 12.28 V
Run - 11.58 V

I also checked the other fuses, and didn't find anything that seemed out of the ordinary. The 700 mV difference between accessory and run seemed a little strange to me. Could this indicate an issue with the ignition switch and/or could the 48 mV at key off be enough to run the display as long as fuse 19 isn't pulled?

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30 Aug 2019 21:06 #33307 by ontheriver
Check at the battery for voltage,in acc. and run,both seem low

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07 Sep 2019 18:54 #33465 by Brocktoon
I think I've finally figured out what was going on. It seems to be a problem with the radio itself. I searched around the web for anyone else who had the same problem, and one forum had a post that mentioned a blown diode in the radio being a possibility if the battery had been quick boosted (40 amp), which I had done for the first -- and likely last -- time. Threw an aftermarket head unit and adapter harness in, and it's working great. Just to be sure, I tore open the stock radio and checked the diode next to the harness port. Voltage in both directions.

As for the power mirrors, it looks like a switch problem. Both mirrors move down, but that's it. I checked the wiring, and even though there was continuity, someone besides me had been there before. Instead of a yellow wire that splices out to each mirror, they were all red, with an uninsulated splice connector, and "one of those" tape jobs. You probably know what I mean. I'm still wiping crap off my hands.

Anyway, just wanted to make this post just in case the other two or three people who still have one of these trucks AND the stock radio has a similar problem. Nothing worse than finding a post describing the same exact issue, but no solution to go with it.

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