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Formerly p**sed, truck fixed now. thanks to all


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So... foggy in denver this morning, left my lights on all day. :doh: Asked one of the guys at work to give me a jump. Didn't pay much attention to his side of the cables.....and he reversed them on his truck. Long story short, smoke escaped from some lucky component and I am stuck waiting for a ride. Currently looking up a list of items that might be hard to get from Checker.

Anybody ever have this and what did you need to replace? I did notice that the fuse link "A" is missing insulation now to the starter relay. I can get the truck to run if I am patient but guages are sweeping funny and the park brake and seat belt lights illuminate when I open the door. Looking through manuals now, certainly don't have the tools to do anything until the weekend.

 

Other symtoms: Intermittant electical power to maintain a running truck, tach does 360's, battery guage goes to discharge.

Where is Mr. Hornbrod when you need him?

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I'd start with the starter relay and the fusible links that are attached to it (these are the majority of the fusible links in the truck). Failing that, the alternator stator might be fried, and unless you know a really reputable re-builder, I'd go with a new one.

 

Now would also be a great time to replace all the positive battery cables with 2 AWG ones, as thier probably needing it as well.

 

Good luck

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I'd start with the starter relay and the fusible links that are attached to it (these are the majority of the fusible links in the truck). Failing that, the alternator stator might be fried, and unless you know a really reputable re-builder, I'd go with a new one.

 

Now would also be a great time to replace all the positive battery cables with 2 AWG ones, as thier probably needing it as well.

 

Good luck

 

Agree w. all the above, as well as replacing all the negative mains cables too. Fusible links are slow reacting, and usually before they toast all the more sensitive electronics go first on a polarity reversal, i.e. meter movements, relay coils, sensors, and the ECU. I'd much rather have a current surge than a massive polarity reversal; much less damage. Don't envy you mate. :(

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Friggin idiot, you figure he would have payed some more attention.

 

Ya bro, check your grounds as much as you can, anything that looks discoloured, change. Oh, have you unhooked your battery yet, I don't know what it does to our trucks, but I know on my grand prix, it resets EVERYTHING. Maybe she just needs a breather without power for a while??

 

Had an incident a while ago while riggin up underglow, and I pinched the wires, there was an assload of smoke, but only because it grounded, I checked the grounds and everything was good.

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Fusable links and ground loops are tricky. I think you probably have both of them. First the fusable links. These are slow blow and try to protect your circuits if a short or something were to occur. If the reverse voltage was done the links are probably bad, I usually check them by doing a visual meaning hold them in your hand and rub the wire on either side of the black cover. The fusable part is the wire that is kind of rubbery. If it feels streched or mushy cut them out and get some new parts store waterproof fusable links. Don't forget to size the fuses correctly!!!!! They is usually labeled writing written on the wire.

 

The problem with the lights coming on from opening the door is probably a bad ground. The way voltage works is positive 12v will always try to find a ground in a circuit so if the ground is deterriated crazy things can happen like when you press on the brake and the wrong light bulbs go on and off for instance or get dimmer. Check your body ground at the battery, the small one attached at the fender, if you can't tell it's bad get another piece of wire to temp jump the existing one.

 

And the last but first thing I would do is get another battery, 12V batteries are made up of 6 plates consisting of 2.11v a piece, if the battery was still hooked up one of these plates are probably shorted. You will not get enough voltage for your components or at worst the battery will blow up if you try to charge it.

 

Hope this helps and by all means take pictures if you need further assistance.

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Well, went to the store, tested battery (toast) replaced it, the starter relay, fuel pump relay,latch relay. Checked the wires and fusible links physically today, but with 23 yr old wires they all kinda felt rubbery, especially the orange one with the blade connector. I am headed back out tomorrow morning with a multimeter and wire diagram to test the power wires for a short to ground. will also crawl underneath to check the ground at the starter. The ground from the battery to the block and from same post on block to the frame appear solid. I did hit the key after replacing all the parts, it did fire up. I let it idle for a bit and got the fluids up to temperature when it started to run intermittantly like something was shorting to ground. crazy dimming lights and 360 sweep on the tach. while watching this for a bit, i spent some time wiggling the fusible links and relay bank, but it didnt appear to make a difference. Eventually, the truck died. I could get it started again, but it runs like poo when warm. Disconnected the battery when I left, as I did not need to drain the new one down.

I need to get a photo account up to post pictures, may do that tomorrow if I find something. Otherwise I will tow it home.

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I am headed back out tomorrow morning with a multimeter and wire diagram to test the power wires for a short to ground. will also crawl underneath to check the ground at the starter.

 

I forgot to mention, you need to test the fusable links with a good heavy duty test light. This may seem crazy, but you will get voltage through a bad link, but current will be restricted. So a load will need to be put on the circuit to test it. Ground the alligator clip directly to your battery post and probe the circuit with the light. If the light goes dim after testing said circuit or the fusable link heats up or smokes it's bad.

 

Did you check the body ground on the fender yet? The one on the block isn't that good because of the rubber engine mounts. If it starts and the gauges go crazy it's probably the body ground. It seems crazy of the manufacture to install a #8 ground wire to a 100A fuse block or bigger. I try to upgrade that ground because it is so accessable and only about 10" long. If you do make sure the permanent one is soldered and crimped so it doesn't degrade over time and cause you the same problems.

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Towed it home today, too windy and cold to do anything. supposed to warm up tomorrow. Did locate an 87 ECU at the junkyard (not pick n pull) for $60. Will pick that up monday. Truck will run okay cold, long enough to get it on the trailer. but dies as soon as the coolant warms up.

Tomorrow, will pull ECU, alternator, check all fuses and start looking at wires. Will let you know what I find.

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Well replaced all the fusible links today, checked all fuses. It started, ran well. Had the lights on while running around the truck looking at things. Let it idle and rev for about ten minutes. Decided I might test drive, stepped on the brake and truck died. lights did there crazy thing and....

Guess I will pull the rear light and check the ground there. Alternator was charging, and it is the weekend, so no chance on an ECU. If the ECU was bad, would it run at all?

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Will try that this afternoon. I also purchased a new negative cable and will utilize the ground strap that it comes with today. Barring that I will hook up a light in between the post and cable and start disconnecting items from the start solenoid until (or if) I find something draining the power. Thanks. Will definitely post up the "cure" when I find it.

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Okay, did what was suggested, plus a couple of other things, have two questions for electrical gurus before I officially call it fixed.

question 1. I removed the negative cable from the battery and set up the multimeter between the post and the cable. I then started to remove the fuse links from the starter relay as I was showing a 12v draw. when I removed the one for the alternator, it went away. Should this show voltage with the key off?

 

question 2. I could not get power after the warm up until I put a jumper to ground. Everything worked great including voltage from alternator at 13.5. I checked all grounds for security but did not find one that looked bad, but did not ring them out. I guess I will put one in permanently from the post to the frame. Will this cause any issues that anyone can think of?

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I really don't understand what you are doing w. the multimeter checking voltage? If you are looking for a partial short causing current draw, the best way to do it is to use your multimeter on the 10 AMP scale. Most all decent multimeters have a 10AMP scale; you have to plug in the test leads to the COMMON (ground) and 10A meter jacks. Hook up the multimeter is series with the disconnected NEG cable and the battery NEG terminal, then check for a amp reading w. the key OFF. If you are getting an amp reading, start pulling the fuses one by one until you lose the amp draw. And yes, the additional ground cable to the frame is okay. :cheers:

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A digital multimeter set to a voltage scale has an incredibly high impedance. On the scale of a few mega ohms. Just a clock or radio pulling a few milli amps to not forget the time is more than enough to show the 12V between the battery post and the cable.

 

If you're looking for a short, you need to look how much power is being drawn, not potential between a disconnected battery post and cable. For this you use the 10A setting, as Hornbrod already said.

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A digital multimeter set to a voltage scale has an incredibly high impedance. On the scale of a few mega ohms. Just a clock or radio pulling a few milli amps to not forget the time is more than enough to show the 12V between the battery post and the cable.

If you're looking for a short, you need to look how much power is being drawn, not potential between a disconnected battery post and cable. For this you use the 10A setting, as Hornbrod already said.

 

I'm sorry. I know enough to be a danger to myself and others when it comes to electrical troubleshooting :dunce: My background is mechanical, and specifically turbine engine technology. We only ring out wires for electrical continuity, if they are bad, there is a whole differenct class of folks who work them for me. The good news is I have been able to somewhat follow the suggestions to get me to the point that I believe the truck will be fixed today.

What you guys are saying about current draw makes perfect sense and something that I had forgotten about. Will check that when I get back out of work today and update what I find.

Thanks!! :bowdown:

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:cheers: to all the great suggestions helping me through this. After changing out the following:

(items confirmed toast from crossing jumper cables)

New battery

New Starter relay

all the fusible links to the starter relay

and replacing ground cable as well as adding two new grounds to the body. The truck LIVES again.

I have no current draws when tested every thing but the radio works (has an inline fuse that I am sure is gone, but will fix later). Drove around town for 30 minutes this evening and will venture the 50 mile drive to Denver in the a.m.

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