70 Challenger no power after swapping in new electrical harnesses

[Ricomondo]

I replaced most of the wiring harnesses in my car as they were spliced five ways to Sunday; Rear light harness, under dash, and forward light harness
After buttoning everything back up, I have no power to the gauges, lights etc.

This is the current state of the car: Neg cable: one end grounded to the rad support (connection cleaned) and the other end of the cable to the passenger side cylinder head (connection cleaned)  Positive connected to the starter. Forward light harness is also grounded to the rad support.

The standard dash is bolted to the metal frame for ground, the light bar is plugged in but not installed.
The bulk head on the engine side, all connections appear to be snug?

Its not the battery as I took the battery out of my 4Runner and still nothing.
I will say I took a screwdriver and touched the started relay and it cranked?

It's probably something simple, but what can I be missing here?

[anlauto]

Did you tighten the two nuts on the back of the AMP meter ?

[6bblgt]

fuseable link connected to the starter relay?

[Ricomondo]

Did you tighten the two nuts on the back of the AMP meter ?

I will pull back out and double check Alan

[Ricomondo]

fuseable link connected to the starter relay?

Yes - new starter relay and its hooked up

[Ricomondo]

I will say I installed new repop OER stock gauges as well. Hopefully its not something with them?

[ragtopdodge]

Ground the back of the gauges themselves.  Also on the switch panel.

I always do that to get the wipers to work.

[edison1970]

Get an ohm meeter and a test light and I would start with the wiring at the fuse block to see if you have power and work up to the components on the dash.

[VCODE]

Did you check the fuses. Check all of them with a test light or meter. You would be surprised.

[70 Challenger Lover]

In getting my RT back on the road recently, I went through the exact same thing you did. It was frustrating but it will be much easier on you if you take it one step at a time.

First of all, sometimes you can get lucky and one little fix like a bad ground fixes everything. Often times that is not the case. The car is fifty years old and probably had ten different things going on even before you got it.

If everything worked before and then all of it stopped working after putting in the new harness, then you could conclude it has something to do with the new harness connections. It sounds like nothing was working right before so you need to be systematic in your approach.

I found the plugs to the column under the dash were not fully seated which caused intermittent failures with my electrical systems.

My gauges still would not work but the ammeter did. I checked that I had power going to the voltage regulator at the back of the gauge set. It did but no power coming out to the gauges themselves. I pulled the voltage regulator and replaced it with one I had just bench tested and gauges worked after that. The ammeter works independently because there is no voltage reduction. It gets the full power in and out to register charging and drops.

My horn wouldn't work and for the longest time this really vexed me until I finally realized the horn relay snaps directly into the fuse block. I dug it out of the box of leftover crap I found in the trunk and now I had horns.

My brake lights would not work and eventually it occurred to me that they wouldn't go on if the switch at the back of the pedal is misadjusted. I checked that and I found it was a little too close. The only way the lights would have turned on is if I forced the pedal most of the way to the floor. After a quick switch adjustment, brake lights worked great.

Tail lights weren't working but that turned out to be a crappy rear wiring harness. At the same time, I found the old gas sending unit wire wasn't fully seated. Once the new harness was in and this wire was fully seated, I regained a gas gauge reading. The rear side marker lights requires a good body ground and with a new wire harness, you will still have to seat the bulb in the housing to complete the ground circuit. Use only new bulbs. They are cheap.

Front turn signals also require a good ground. I recommend bench testing them first. The pigtails and bulbs fail easily. Front side marker lights don't need a ground as they have two wires on the pigtail but these pigtails also fail easily so bench test the lights first.

I could go on and on with all the electrical gremlins I had to chase down but the point I wanted to make is you probably will have to diagnose each thing one by one. I'd start with the gauges since they are easy (with the seat out obviously). If you aren't getting power from the harness to the voltage regulator, the problem will likely be with how your new harness is hooked up.

Don't forget to install fuses in your fuse block. I know this sounds ridiculously obvious but My heater fuse was missing and I felt pretty dumb chasing down stuff only to reach the fuse block and realize how simple the fix was.

[anlauto]

I find sometimes too with the "new" harnesses, the brass connections aren't fully clipped into the connector, so sometimes when you plug the harness into the bulkhead, the wire actually pushes out of position not making a connection. I take a little screwdriver and push each wire in separately just to double check. 

[Ricomondo]

Pulled the gauges back out. Everything looks to be tight.
anything look out of place?
I'm using a factory FSM as well as the old harness to se where everything goes.

[Ricomondo]

Did you tighten the two nuts on the back of the AMP meter ?

Yes Sir. Nice and snug

[dodj]

Get an ohm meeter and a test light and I would start with the wiring at the fuse block to see if you have power and work up to the components on the dash.

This...or close to it. I would unplug the bulkhead connector with the larger gauge red wire and test it for power
You need to see if you have power to the bulkhead connector first. Then you will know if your issue is in the engine compartment or behind the dash.

If it ends up being within the dash, I would start with ragtops suggestion and run a separate ground. If you recently painted everything, you may need to scrape some paint to get your dash working.

[Ricomondo]

Solved the issue - my dumb a$$ had the middle bulkhead connector inverted (upside down) Once I flipped it around, got my power and lights back. Man I feel silly.


Thanks everyone for trying to help! I really appreciate it. Man, I've done his wiring harness swap three times on different cars; obviously missed this step....