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85' 720 - Nothing but Headlights


mmitchell57

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The Blue/Red stripe wire on the 4 way flasher should have power at all times. The fuse to check is the 4th  one over from the front.

 

You already said you replaced or checked it and it was fine. I guess check the fuse holder... you should have 12 volts on one of the terminals. If the fuse is good you should have 12 volts on the Blue/Red stripe wire on the 4 way flasher. Fix this

Ok, i'll check these when I get started on it tonight. If I don't have power to the fuse block on that 4th fuse, while the truck is running, what do I need to look at? I'm going to pull the cluster back out to make sure something didn't come loose when I was putting it back together the other day.

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I went a head and pulled the cluster out just to see what I've missed. I found something I hope you guys can help me pinpoint..

 

421210_10151809209446204_450937732_n.jpg

 

The connector is the one between the wiring harness and the hazard switch.  The connector I'm holding goes into the connector from the harness side and connects to the green/white wire on the hazard switch side. The bad part about the connector i'm holding, it's not connected to anything and is the only wire into the connector for the green/white on the other end.  I'm assuming this is why the green/white isn't powered an might be the source of the issue.

 

when I tested the fuse yesterday w/ the multi-meter I didn't get a current while the truck was running. i'm going to do some quick research and head back down to test, search and attempt to fix the issue.

 

*edit*

 

Also found a connector at the back of the cluster that was purple wires and it was not connected to anything either.

998703_10151809209006204_524765813_n.jpg

 

Worst case here, i'm pulling the dash to get a clear view of reality and test things till I get it working. It was working before I pulled the dash so I'm sure I missed something.

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This fuse should have power all thetime NOT just when the motor running. 4 way flashers are no good to you if your motor quit. Horn, interior light, brake lights, headlights, dash and marker lights, clock are all things that have to work at ALL times.

 

If you count the fuses from left to right the 8 9 10 11 12 and 13th ones all are powered directly from the battery. They also have to pass through one of the two GREEN fusible links located very close to the positibe terminal of the battery. There should be two GREEN and one BLACK fusible links there. Ther are about 4" long with connectors on each end.

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There are two plugs that could be in your wiring harness that might not be used, one is for a clock, the other for a tach, the clock plug has a green/black wires(82 diesel wiring harness), and the tach I don't know because as I said, mine is a diesel.

Here is a fusible link on a diesel, it has 4 wires.

DSCN0028.jpg

Here is where it is located on my truck, it would be connected to the positive battery post.

DSCN0080.jpg

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This fuse should have power all thetime NOT just when the motor running. 4 way flashers are no good to you if your motor quit. Horn, interior light, brake lights, headlights, dash and marker lights, clock are all things that have to work at ALL times.

 

If you count the fuses from left to right the 8 9 10 11 12 and 13th ones all are powered directly from the battery. They also have to pass through one of the two GREEN fusible links located very close to the positibe terminal of the battery. There should be two GREEN and one BLACK fusible links there. Ther are about 4" long with connectors on each end.

A light went off in my head after I read about "fuseable links" that makes the most sense.  I'll take a look when I get home.  The other fuses appeared to be good w/ exception of this one. Based on the frying of the fuses before when I hooked up the cig lighter wrong, I'm willing to be the fuseable is gone.  I had an 89 pathfinder for a while and it had one go, i'm guesing the links will look about the same on this one when fried?

 

There are two plugs that could be in your wiring harness that might not be used, one is for a clock, the other for a tach, the clock plug has a green/black wires(82 diesel wiring harness), and the tach I don't know because as I said, mine is a diesel.

Here is a fusible link on a diesel, it has 4 wires.

DSCN0028.jpg

Here is where it is located on my truck, it would be connected to the positive battery post.

DSCN0080.jpg

Yep, I have those in the engine bay. I didn't realize they were fusables. I'll take a look. It's the only thing that makes sense at this point.

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The fusible link is a wire with a special Hypalon plastic coating that can survive high temperatures and is resistant to catching fire. All or most electrical circuits are fuse protected but what protects the wire bringing power directly from the battery to the fuse box??? This is what the fusible link is for. Among other things a catastrophic accident might crush these battery supply wires and rather than have a fire the wires inside melt just like a fuse. 

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Try wiggling them while testing them. They could be melted inside the insulation and making poor or no connection when plugged back in.

 

 

If the fusible links check out go back to thew fuse box, pull out the 4th fuse from the far right and check for power on one of the terminals. (could be top or bottom I forget)

 

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The Blue/Red stripe wire on the 4 way flasher should have power at all times. The fuse to check is the 4th  one over from the front.

You already said you replaced or checked it and it was fine. I guess check the fuse holder... you should have 12 volts on one of the terminals. If the fuse is good you should have 12 volts on the Blue/Red stripe wire on the 4 way flasher. Fix this

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We've already covered this fuse before.

 

 

The fusible links appear to be fine. You checked the fuse and it's fine so how is power NOT getting to the 4 way flasher????

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Ok, just tried something I haven't before. I tried the positive side of the fuse to the firewall as a negative and I got 12+volts. This is on the 4th fuse from the front for the "stop lights". I then tried the positive from the 4 front the firewall to the negative on the 3rd from the firewall and got 12 volts.  So, it appear to be as someone else suggested, a ground.  Geez.... This is killing me.  I willed the heck out of the fusables and their connections. No love. I did notice when I turn on the hazard that the parking lights all turn on but don't blink. This is w/ the dash out and the cluster plugged in.

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Is this with the fuse IN or OUT??? If with the fuse in you will read 12 volts on both sides. How could you not???

 

 

So fuse has power then.

 

Go to the 4 way emergency flasher.

 

 

 

Starting to go round in circles....

 

 

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The Blue/Red stripe wire on the 4 way flasher should have power at all times. The fuse to check is the 4th  one over from the front.

You already said you replaced or checked it and it was fine. I guess check the fuse holder... you should have 12 volts on one of the terminals. If the fuse is good you should have 12 volts on the Blue/Red stripe wire on the 4 way flasher. Fix this

 

Ok, i'll check these when I get started on it tonight. If I don't have power to the fuse block on that 4th fuse, while the truck is running, what do I need to look at? I'm going to pull the cluster back out to make sure something didn't come loose when I was putting it back together the other day.

.

 

So we are back to the 4 way again. Check for power on the Blue/Red stripe wire.

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yeah, I realized that too, but I didn't know what else to do. I figure it out. There's 2 plugs in the wiring harness that are identical. Plugged into the other one and it works. The one that is the correct one is in the harness that runs behind most the stuff in the dash and only pops out near the steering column. The other is at the end of the wiring harness that the cluster runs on. swapped em, bam, good. Only issue now is the dash lights. I'll worry about those tomorrow. Dash is back in w/ all the other stuff. Just left the cluster loose to screw with it tomorrow.

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Yep, it caught me off guard since that's not typical in any vehicle i've dealt with. That why I stuck with the plug I had for a week. Eitherway, I learned alot and decided to use it to figure out what's up w/ the dash lights. I get power up to the plug on the dash for the lights. Looks like they all run off one circuit via the wiring harness. When the plugs is in the cluster, I get .08 volts at most with it varying between .05 and .09. I guess the there's a ground or the green board / paper is bad. I already put it all back together and drove it to work this afternoon. Drives great with the new brakes installed today. Those drums are a nightmare.

 

Anyway, dash light, I'll see if they are still broke tonight after cleaning the contact on the green board / paper. If not love, I won't cry to hard. I wanted a new cluster w/ the tach and clock anyhow.

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Yep, it caught me off guard since that's not typical in any vehicle i've dealt with. That why I stuck with the plug I had for a week. Eitherway, I learned alot and decided to use it to figure out what's up w/ the dash lights. I get power up to the plug on the dash for the lights. Looks like they all run off one circuit via the wiring harness. When the plugs is in the cluster, I get .08 volts at most with it varying between .05 and .09. I guess the there's a ground or the green board / paper is bad. I already put it all back together and drove it to work this afternoon. Drives great with the new brakes installed today. Those drums are a nightmare.

 

Anyway, dash light, I'll see if they are still broke tonight after cleaning the contact on the green board / paper. If not love, I won't cry to hard. I wanted a new cluster w/ the tach and clock anyhow.

 

Remember there is a dash light adjustment knob next to the lighter.

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  • 9 months later...

Yeah, checked out the bulbs and they all pass the checks w/ the multi meter. I've tried everything except for replacing the intentisty knob (ha!). I'm guessing it's a rehostat type control but never messed with it. I did a direct wire to bypass the adjuster and it blew the fuse as soon as it touched down. Not sure what to do at this point.

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Earlier ones are variable resister (rheostat) but later ones are solid state. (well electronically controlled) They are smaller and don't get hot like the others.

 

720dimmerswitch005Large.jpg

 

720dimmerswitch001Large.jpg

 

Three Wires

The Yellow/Red stripe wire is the supply voltage from the light switch which is supplied from the third fuse over from the left side.

 

Black is ground and MUST be grounded to work.

 

Red/Blue stripe is the varied voltage to dim the lamps.

 

Removal

I believe is...  push in firmly on knob and twist to disengage. Lift away. Unscrew lock collar.

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