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Discussion Starter #1
Hello this is my first post.
I bought a 1989 chevy 2500 scottsdale. There are some electrical gremlins going on with the instrument panel.
I had it out and checked all bulbs and cleaned the connections to the gauges.
When I turn the headlights on I can see that both indicator arrows seem slightly illuminated. The gauges move and slow less of a reading. The high beam indicator is slightly illuminated.
Someone did something to the indicator connector, it appears to be broken in half. I cleaned the pins with a fiberglass pencil and tried to put the connector back together. This evening the instrument lights first came on. and then off and it was showing the symptoms I described earlier.
If I don't have to, I would like to avoid having to replace the indicator switch and maybe just replace the connector by pulling the wire pins out and swap them over to a new plug.
I cleaned the ground above the diagnostics connector. Are there others I should look at and clean?
Does anyone have some advise what this issue could be I have described?
 

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It sounds like dirty connections, in particular, dirty grounds.
I think your on the right track.
Maybe a ground a little farther away from the circuit board, like the one(s) for the dash. Sorry, I don't know where they are.
But, here is what I would do, find a good clean bolt on the dash and temporarily run a wire from that bolt to the battery negative.
If nothing changes, you know you have good grounds to the dash; if everything works, the dash grounds need attention.
 

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X3 - there is ground G302 just above the ALDL connector below the steering column, G109 & G110 on the fire wall behind the plastic cover on the passenger side, among others. Look at pages 121 - 138 for more stuff to look at. As @RayVoy said there's nothing wrong with adding an extra ground except when you're running a 4-20 mA circuit (but that was a different lifetime for me, lol),
https://www.mediafire.com/file/4f18bzf7nytb15x/ST-375-89-EDD_1989_T400_CK10-30_Chevrolet_Wiring_Manual.pdf/file

Here's a link to more manuals (thanks to @Hatzie on GMT400.com)...
https://www.gmt400.com/threads/88-95-service-manuals.43575/
 

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I wasn't suggesting during a new ground wire, just a temporary wire to narrow down the location of a dirty ground
That's a great idea for troubleshooting. Personally I don't have an issue with adding a ground either. Years ago I helped a guy with an old Datsun B210 (I think) whose dash lights were acting weird, ran a ground and everything worked fine. The headlights on my 66 T-Bird had the same issue. This was when I lived in WI - lots of salt on the roads and in my cars.
 

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Discussion Starter #9
with the great help by you guys I got that one sorted. 99 more problems to go.

Can a bad engine ground cause the engine to keep cutting off? She runs fine for a while and then just shuts off sometimes.
 

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Discussion Starter #11
It was the turn signal switch connector. At least that is what it seems to have been the cause at the moment. You know how these things can change. But I'll post an update in a few days
 

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^^^ What he said, we'd all like to know your solution for the dash.

Other grounds may cause your engine to shut down if the ECM looses one because it grounds out each injector (power is continuously supplied to them) when the corresponding cylinder on its side is calling for fuel. In essence, they fire off in in a synchronous pattern as the engine rotates (unless there is more demand than they can supply then they go into asynchronous mode and fire together). I had an example of having my Duty Cycle of the injectors go to 106% with WOT at 5200RPM in 2ng gear, had to increase my fuel pressure regulator's from 18 to 28PSI to get them back to ~80% DC. Anyway, there are 2 ground wires for the ECM on one of the studs for the T-Stat housing which are the main grounds for your ECM. If not a ground I'd start looking at your ICM, cap, rotor, and/or coil. Sorry for the dissertation.
 

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Discussion Starter #13
I did clean the ground at the thermostat housing when I changed the thermostat. I did that when I flushed the radiator and replaced the radiator hoses. I also got a new coil, and new spark plugs. The leads looked like they had been replaced. on the right side of the engine is a wide ground step, it looks greenish at places. I'll clean off the engine side and see where that ground strap connects to and clean that too. I cleaned all the pos connectors at the firewall and a ground wire that went there, too. I'll clean the fuel pump ground tomorrow as well.
what about the large square connector assembly left to the brake booster on the firewall? It looks to be 3 connectors in one. Is it good to take that off and clean and grease thereafter?
 

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Discussion Starter #14
So I found some more ground wires. these two were totally rotten. I crimped new connectors on the wires and new star washer installed.
Sill when the truck gets warmed up , she'll just randomly die. Tomorrow I'll replace the distributor caps and rotor and the ignition control module. I hope that'll do the trick.
IMG_8262.JPG
IMG_8263.JPG
 

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That green corrosion rot has infiltrated the entire braid and will not be reliable or make a connection at all. Thoze braided wires have all been removed from my trucks and replaced with 4 gauge coated wires with soldered on terminals. A wire like this will last forever. Also get the metal clean down to bare metal. Get some dielectric grease, this stuff can be used wrong and it commonly is. Put very little on your terminals and the connection point, very very little. Then make your connection and cover the connection with the grease. If you upgrade the ground wires and use some dielectric grease then you will have a protected connection that will not ever fail.

Al
 

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Discussion Starter #16
There is something going on still. I got a new distributor cap and rotor. The ignition module checked out ok. A clue could be that the truck sometimes just clicks instead of turning over. Although, I think that could be a dodgy solenoid on the starter. So I was going to mess with that once I got the truck running reliably. Maybe it's the Plus wire from the battery . I'll look at the ground wire from battery to body tomorrow.
The starts and runs, the suddenly just shuts off. When I try to start again , she'll start for a moment, then back fire some and die. after maybe 3 or 4 revs. Tomorrow she'll start as if nothing had happened. It's really frustrating the crap out of me. The Ignition module would show these symptoms, but it checks out ok?
I like my cucv more and more.
 

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When you're dealing with something failing once the engine is hot, how can you test the ICM on a bench? I've heard you can prove it's bad but you can't prove 100% it's good. There are quite a few folks on 3 different sites (that I know of) that finally drilled down to the ICM. Use only AC Delco or Delphi electronic components (including cap and rotor) and, in case of the ICM, a high quality insulating paste like Arctic MX4 on the bottom plate of the ICM (that keeps it cool) and don't get any on the mounting bolt holes, that's another critical ground connection. My issue with an almost brand new Spectra Premium distributor was it surging while cruising @~2200 - 2400RPM, others had it stumbling at idle. I'm just saying...

Your issue with it not cranking sounds like a totally different issue.
 

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Discussion Starter #18
When you're dealing with something failing once the engine is hot, how can you test the ICM on a bench? I've heard you can prove it's bad but you can't prove 100% it's good. There are quite a few folks on 3 different sites (that I know of) that finally drilled down to the ICM. Use only AC Delco or Delphi electronic components (including cap and rotor) and, in case of the ICM, a high quality insulating paste like Arctic MX4 on the bottom plate of the ICM (that keeps it cool) and don't get any on the mounting bolt holes, that's another critical ground connection. My issue with an almost brand new Spectra Premium distributor was it surging while cruising @~2200 - 2400RPM, others had it stumbling at idle. I'm just saying...

Your issue with it not cranking sounds like a totally different issue.
Arctic MX4 is a Thermal Compound, it's not there to insulate. The bottom plate of the Ignition control Module IS ground. So I am not quite sure what you're trying to tell me here. When it comes to that then copper grease has better thermal properties, than aluminum paste.

When we tested the module it heated up. testing it several times gets it pretty hot. Not sure it will be hot enough to melt the solder inside (supposedly that's why they fail when they get hot), but mine didn't fail even after testing it on the bench for a 5th time.
That doesn't mean I felt any better about this unit, just meant that I was going to re install it and see what happens.
 

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Discussion Starter #19
Now if the plate on the distributor gets hotter than the module itself, then you would use an insulating compound to protect the module from the heat being transferred . It would make sense then to have a separation between the two , since air is a good insulator.
 
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