I am trying to trace an electrical problem and am not an expert on the wires in the dash. On a 70 Challenger, where does the primary power come from to supply power to the fuse block? The only power I see coming into the interior is from the starter relay (the line with the fusable link) going into the bulkhead fitting and into the car. From there it goes to the ampmeter.

I found one short between the red and black wires going to the ampmeter, but fixed them. Problems still continued after that repair.


I do have the wiring diagram for the car, but it really is not helping me. Hopefully someone can give me a suggestion or two (other than buying a new dash wiring harness......)

Thanks,
Dale

check your fusible link . . .

Also check the bulkhead connection. this and the ampmeter are the weak link in our cars. i rewired my 70 Challenger as you would a new project hot rod (small fuse, relays, dependable switches,...). it is a joy to drive and dependable now.

I've got power to the hot side of the ammeter - it is the only spot inside the dash that has power. I assume the FL is OK since there is power on that red wire all the way from the battery, through the fuse block and to the ammeter.

I found a wire diagram for the dash wiring and am trying to figure it out. There appears to be a junction of some sort where multiple wires cross - the one feeding the horn in the fuse block; the one going to the headlight switch; and the one for the battery feed to the fuse block. Not sure what the junction is. I've attached the edited wire diagram showing the wires and junction of concern (at least I am trying to attach it...)

I think I may pull the whole harness this weekend and test each line. If that does not do it, time to get some cash and go with a new set of wires.

See if the downstream terminal on the ammeter is hot. From there it goes to a "welded splice" which is the junction you mentioned. From there it T's off to the fuse block & to the headlight switch & to the ign sw (those are hot all the time). A welded splice failure is rare, I would see what is up back at the ammeter first

Finally got warm enough to go out and work again - the torpedo heater cannot heat the garage up enough when it is single digits.

OK - ammeter has juice on the hot side, no juice on the ground terminal.

I bought an aftermarket voltmeter and hooked it up; no volts until:
1. Turned on light switch (no lights though)
2. Ignition switch on (nothing turns on)
3. Here's the key one I think: with the switch off, touched the test light to the battery side of the fuse block and I get 12V at the voltmeter, but the test light does not light (and it does when touched to the voltmeter hot wire, so it is working.)

I really think I have a dead short somewhere in the harness. I unhooked the lights/wipers/horns/steering column and still could get no juice to the fuse block. In the past it would get juice after a while but not now.

At this point I want to find the problem even if I decide on a new harness. It is irking me beyond belief now.......!

Had similar problems with my 71 Charger recently. Here's a basic diagram from the mad electrical site that helped me a lot. I'm no Ace when it comes to electrical either.

My problem was a direct short at the ammeter and had to bypass it(connected the red batt and black alt wires together). I'm in Syracuse. PM me if you'd like, hopefully I can help.

Thanks. I am going to go out and try something based on this.

There is no ground terminal on a amp gauge. The power just passes through it. If you don't have power on both terminals then the gauge is bad and that is your problem. Put both wires that go to the amp gauge together on one terminal, it doesn't matter which one, and I'll bet your problem goes away.

I jumped the terminals on the meter and surprise, everything started working. Thank you for clarifying the ground/positive. I assumed it was a ground, but now it makes sense.

The only bug in this is that I had just hooked up a brand new voltmeter to ignore the ammeter in the dash. If the problem was in the ammeter, the new voltmeter should have solved it (at least I thought it would..)

This all started after I hooked up the horns and horn relay. After "honking" the horns the first few times, everything started. This kind of repair makes me nervous I still have a problem and am risking a fire while driving down the road.

Thank you to all!

What Stump said. (1) pull a batt cable off (either one) (2) put the black wire eyelet on the ammeter stud along with the red wire eyelet that is already on it (both ring terminals on same stud) (3) with door shut/everything off touch the batt cable you removed back to the post & if no spark then go ahead & install it & go inside the car & see if you are good. Not sure if you have a clock or something that is on all the time but if it sparks heavy when you do (3) then do NOT reinstall the cable as there is a dead short somewhere but I believe we are dealing only with an open but I dont want to chance frying the FL. Holler back. EDIT Just saw that you confirmed that it was the ammeter. dont forget to pull a batt cable first when you are up in there

What Stump said. (1) pull a batt cable off (either one) (2) put the black wire eyelet on the ammeter stud along with the red wire eyelet that is already on it (both ring terminals on same stud) (3) with door shut/everything off touch the batt cable you removed back to the post & if no spark then go ahead & install it & go inside the car & see if you are good. Not sure if you have a clock or something that is on all the time but if it sparks heavy when you do (3) then do NOT reinstall the cable as there is a dead short somewhere but I believe we are dealing only with an open but I dont want to chance frying the FL. Holler back

The volt meter wouldn't do any thing to fix the problem because it just reads voltage. Power will not go through it to the rest of the circuits. An ampmeter is kind of like a straight wire that creates an magnetic field that moves the needle as the system draws power. A voltmeter reads the amount of charge in the system. Basically a voltmeter is a dead end street and the ampmeter is an expressway. All the power comes through the bulkhead connecter to the amp gauge and from the amp gauge to the rest of the system. The amp meter is always full battery power. It never shuts off and a voltmeter does.

I have been reading some repairs for this system, bypassing the ammeter and even the bulkhead fitting connection for these wires. I like what I am seeing and will work on doing that. It would make me feel a lot more comfortable. (MADelectrical.com)

Thanks Stumpy - the ammeter/voltmeter expressway/dead-end reference explained it perfectly.

Time to get out the soldering gun and buy some heavier gauge wire than what I have in the tool box!

Be careful with the ammeter studs. I had trouble getting the red wire off as it was corroded on the back of the ammeter. This caused the studs to loosen. I tightened them back up but unknowing to me broke one or two of the isolators which caused it to short at the gauge cluster.