15a fuse blowing... also won’t start.
 

I’ve scoured this forum for days reading over and over all of the people’s posts with problems similar to mine.

First off, bare with me. I lost my uncle this year (practically my dad), the only mechanic in the family. So I don’t have much help anymore from an expert and my mechanical knowledge is pretty basic.

Recently my little brother borrowed my truck. The battery has had a parasitic drain it seems and it wouldn’t start for him. I think he swapped the cables to jump it and was too embarrassed to tell me.

My dome light, cargo dome light, ignition switch light, stereo, door locks, and turn signals aren’t working. I checked fuses and replaced the bad ones including the 100a ALT fuse. Of course, it’s blowing the 15a dome fuse every time I put one in.

My electrical knowledge is pretty slim. I have a light tester, and a multimeter (although YouTube is basically the only way I know how to use it.)

I pulled my car in my garage and began following instructions from @TheDurk and others posted here. I’ve pulled the plugs? behind the fuse box in the truck, and I believe I narrowed the ground short to 1A. When it’s pulled, the 15a fuses don’t blow. I’ve printed every diagram, but I’m not sure what exactly to do.

After trying several things mentioned in the forum, for some reason now my truck will crank but no longer start. I’m not sure if I’ve done something in this process to cause it or what the problem is. Did I unplug something?

Any ideas? All help is much appreciated...

Just a guy taking shots in the dark asking ole Unc in the sky for guidance, but he’s probably busy with his own car.

I honestly dont know what to suggest to help you. Have any buddies that are good with electrical wiring to help you figure this issue out?

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long shot but have you checked the fusible links? i had the one near the ABS blow out and nothing worked. you can usually see if its busted through the clear top.

edit: that might be what you meant by 100a ALT

I'm far from an expert but if it were me i would start testing wiring for continuity and checking grounds until i found one that isnt registering right.

pull the spark plug wire on the driver side front cylinder being careful not to damage the wire. place a screw driver that fits inside and touches where the plug clips in and stays there even if you have to use a little electric tap to make sure it keeps contact. Now place any metal part of the screw driver with in 1/4 inch from any metal on the engine then have some one crank the engine over for 5 seconds at a time and see if there is if there is a spark that happens. If there is a spark good if not electrical is the problem.

You could also try taking off the air horn open the throttle plates by hand and take about 1/8 cup or less of gas ( a good splash ) and toss it in. Re attach the air horn and turn the engine over. If it runs for about 3 sec then the you are looking at a fuel problem like a bad fuel pump if it does not then the secondary electrical (spark plugs, coils , ECM computer maybe bad)

These two test can give you a place to start to start to see what part of the system has the problem.:banana:

So what all exactly dead. The dome is shorted you think. Are all other fuses intact?

Do you know how to do basic continuity tests with a meter?

Like another user suggested can you verify all the fuse link are good?

Will the engine crank when the key is in the start position?

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So, something downstream of the DOME fuse is shorted.

The DOME fuse is constant power (always provides power when the battery is connected).

Things that it powers (most of which you already found):
- Interior/dome lights
- Integration relay
- Seatbelt warning
- Clock
- Cruise control (constant power, not main power)
- ABS (constant power, not main power)
- Radio and power antenna (constant power)
- Maybe a few other things I missed in the diagrams

Major suspects that might be the problem are:
- Integration relay (part of the fuse box on the drivers side under the dash)
- Cruise control
- ABS
- Radio

The lighting circuits shouldn't care if they were powered 'backwards', it will be the 'computers' in the car that would be ruined by an event like that.

You'll need to try unplugging each of those systems and see which one stops the fuse from blowing.

-Charlie

Do you have a powered amp, aftermarket HIDs or anything aftermarket that has an external fuse? I had the exact same thing happen to me and it was blowing 15amp dome fuses like crazy. I noticed that the fuse for my powered sub was also blown. Changed that and added a new 15 amp fuse for the dome lighs, and boom, fixed.

Did you check the fusible links might be blown. you have to pull the fuse box out of the housing to replace those. In the middle of @sleepydad video on you tube he shows how to pull the fuse box out.
YouTube

Wouldnt the rig start though if only the dome circuits were out?

I am wondering if the reverse polarity took out the ECM as to why it work start.

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I think there is a good chance that the ECM could be the cause if he had one at hand he could try and do a swap. A junk yard one would be the cheapest option but there could be a chance you would be pulling a bad one. If he is blowing a fuse then that must be addressed first either repairing the cause or disconnecting the whole leg as long as it does not power something important.

Isolation of the problem being fuel or spark would be where I would start. :tongue:

Sounds like it started for a while, then stopped after some debugging.

The diagrams don't have a unified drawing that shows what goes through wire harness connectors, or the debugging would be easier...

-Charlie

Oh I thought possible jumped with reverse polarity as little brother borrowed it and because it had a parasitic drain. He jumped it wrong. As the battery too low to start. Hence why I wondering if his ECM got baked.

I was hoping since his uncle passed a buddy could show and teach him how to check these circuits. That way he be able to find the source.

Very true on the unified drawing.

Parasitic drains can be extremely hard to track down sometimes. Mostly I start with the circuits that are in the door and tailgate jams especially that rear tailgate as those wires have a tendency to break or short together at times. :(



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The 1A connector has on it:

1 - G-Y, RH turn signal indicator power to gauge cluster
2 - G-B, LH turn signal indicator power to gauge cluster
3 - empty
4 - G, 20A Wiper fuse power to power window relay
5 - B-W, LH rear door courtesy switch
6 - G, back window control switch illumination power
7 - empty
8 - B, power output to rear window defogger from defogger relay
9 - empty
10- empty

Which is odd, since none of those seem related to your current problem?

-Charlie

put jumper cables on a dead battery in reverse,, PCM is a failure.

So for members following this screw up , you put the jumper cable on the engine block on both vehicles ... then put the positive cable on the battery positive terminal.

battery drain can be a dead battery. another cause can be a interior lamp stays on .use a clamp on current meter current should be less than 20 ma .. if its above 200MA then pull fuses to find out what circuit is the cause.

junk yard PCM is cheap but you must put the proper PCM for your model year and vehicle..

door locks have diodes so because the jumper cables were reversed then the diode will short out.
door locks have coils and the diode stops the spike surge when the lock operates..
ac compressor clutch has a diode also .. relays also have diodes across the relay coil.
this could be a very expensive mess..

that is why I clamp on the jumper ground cable to the engine block ..

Unfortunately no. I'm the "mechanic" of the group of life long friends... Basically, the brake changer. Ha!