Another dumb wiring question

[cruisenator]

I posted a thread awhile back about wiring my cruiser. I have gotten it pretty much finished (just re-worked not re-done) and I had a few glitches after getting it put back together. The one I will ask you guys is that I blow my headlight fuse as soon as I connect the battery (as well as horn but for some reason the two have a connection on the fuse panel). I realized that I have a bad ground, bad wire, etc. somewhere so I checked everything today (did the grounds again, checked all connections, etc.). Here is my dumb question with all that unnecessary background: I pulled my instrument panel to make sure it was not an issue in there shorting it out and realized that the instrument panel is not grounded. I have not traced every wire going from the instrument panel to see if there is a ground in there somewhere. Does my instrument panel have its own seperate ground??? If so I may have pulled it out when I was getting into the wiring in there and disconnecting the speedometer. I did not see a "spare wire" that could have been the ground but it is possible it is hiding somewhere. Can I just run a seperate ground for it if necessary??? Thanks for the patience.

 

[cruisenator]

one more thing

If I do run a seperate ground, does it matter where it is connected on the instrument panel/truck?

 

[Fast Eddy]

Guessing here, but the panel probably just grounds through the mounting screws to the dash.

If you're popping fuses that easily, the offending circuit should be easy to trace with a multimeter. Put it on 'beep' mode and find one of the wires in the plug to the switch that is grounded. It could be in the instrument panel since there are lights in there.

 

[Magnum44]

This may sound like a stupid answer but you do have relays for the horn and headlights don't you? If not you probably need them. I am just answering off the cuff but what the heck.

 

[Azrael]

Guessing here, but the panel probably just grounds through the mounting screws to the dash.

I'm somewhat positive this is the case.

 

[cruisenator]

doh

I'm somewhat positive this is the case.

Of course, I guess I was just over-thinking it-if that is possible..

 

[cruisenator]

uh-huh

This may sound like a stupid answer but you do have relays for the horn and headlights don't you? If not you probably need them. I am just answering off the cuff but what the heck.

Its a "painless" harness

 

[Pin_Head]

If the headlight fuse blows with the switch turned off, then you have a short in the wire somewhere between the fuse block and the switch.

 

[bsmith123]

shorts and grounds

IF you have a short (and you do) you're not going to cure it by grounding the panel. lets just say you had a high resistance short to the panel. if you add a ground from the panel you're just adding fuel to the fire by lowering its resistance and allowing an even greater flow of current. See what I mean?

I looked at the schematic and the only ground in the panel I saw was the high beam indicator. The other stuff seem to have a 2 wire connections -pwr and ground elsewhere. wires could be shorted together

Generally speaking a one wire connection means a chassis or case to chassis ground. with the one wire being the power wire. the power can short to ground through a bad component allowing continuity to the case as in the HB light. normalluy a light will just give you an open circuit so maybe a bad example

Normally the power runs through a component with a certain amount of resistance then on to ground. The resistance acts like a restrictor controlling the flow to ground. Having a short means the voltage has found a better ground and is now flowing out of control heating up and blowing the fuse.

current flow does create heat but the circuit is planned by wire size, resistance, and voltage to control it and only flow what the wires can handle. A fuse is calibrated to handle less than a wire can and protect the wiring.

One way to tackle this without meter skills is to go around disconnecting everything you suspect then connect up one wire at a time until the fuse blows.

First I would change the horn and light relays or remove them one at a time and see if either is blowing the fuse or you can jumper the wires together with the relay removed and see if it still blows

Personally I would shoot the wires using an Ohmmeter and the schematic --power off, with the battery disconnected. You may shift something and get some smoked wires.

Whatever is shorted is obviously after the fuse not before it

disco the horn first and see if it still blows

look at the back of the inst cluster and make sure a hot wire is not connected to the ground side of one of the components?

relays hooked up correctly?

google OHMS Law--knowing this and use of a meter are the most basic of skills for circuits and will pay off when troubleshooting

be methodical test and eliminate

Have a look at Coolermans site for an FSM schematice. His site is getting to be like a reference library for FJs. He has even documented some of his own troubleshooting and where and what to check and wire colors

FJ40Template2


Best of luck and let us know

 

[captain_morgan]

Remove the culprit fuses. Take a volt meter and set it to ohms. It's usually easier if the meter squeals or beeps, when there are 0 ohms. If you think that the headlights are grounding, place one of the leads into the headlight plug and the other on a good ground, (like the engine.) Do this for all 3. At least 1 of them should cause the device to read 0 ohms. That'll be your ground wire for the headlight. If any others read 0 ohms, you've found your wire. You can probably do the same thing for the Instrument cluster. Just remove the cluster completely and you'll figure out if it's the cluster, or a wire.

With the cluster removed, place the ohm device on the side of the fuse terminal that runs to the cluster. If it shows 0 ohms, you've found that it's not the cluster, but another wire or a miswire... keep searching.

 

[cruisenator]

Thank you

Bsmith an capt'n morgan, thank you for the extensive responses. I will check your ideas today and hopefully get the problem solved. There would be a lot less cruisers on the road without this sight.

 

[Living in the Past]

I know a 69 would have a horn relay but don't think there is a light relay. Should go from your fuse to the light switch then to the high low switch on the floor and then to the head lights. The light switch is designed to handle the load of stock head lights while the horn button won't handle the amp draw of the two horns.

John

 

[DSRTRDR]

when I rewired my cruiser, I just laid a dedicated ground from the instrument panel

 

[Magnum44]

I'll just through something else in for thought. I wired an ammeter in parallel and started blowing fuses and realized my error and wired in back in series which cured the problem. I know you said it was a painless harness but if there aren't any wrong terminations or scathed wires you might just check if you added anything.