Author Topic: No Power after firewall  (Read 441 times)

Offline w100ewd

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No Power after firewall
« on: July 22, 2017 - 11:26:41 am »
I have a '70 grand coupe cuda w/383.  A couple years ago I had issues with the neutral safety switch and replaced it outright.  Since then the car has been running well.  Below I've listed a sequence of things that have been strange involving the electrical system.

A couple months ago when driving for over an hour with the lights on, the lights started to flicker and eventually would completely go out.  The car would still drive and ran fine, but the lights would not come back on.  If I would stop the car and re-start it, the lights would work fine again.

A few weeks ago I started experiencing an even more odd situation.  The car will start right up and I can drive it for 2 minutes or 2 hours, but when trying to start it again the car is completely dead.  I cannot even get a click when trying to restart.  However, if I jumped the car it would immediately turn over.

Now the car does not have power at all to anything: lights, ignition, horn, nothing.  When I put a test light on everything, I have solid power to the starter relay & the starter itself.  The main power cable from the battery shows power into what is block #16 on the first block inside of the firewall.  I however do not have power to the 2nd block in the wiring harness within the firewall.

It seems like there is power coming into the car, but not allowing the power to go out.  Any help and advice is greatly appreciated.  I'm totally scratching my head on this one.
« Last Edit: July 22, 2017 - 11:28:22 am by w100ewd »




Offline 70chall440

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Re: No Power after firewall
« Reply #1 on: July 22, 2017 - 01:47:45 pm »
Sounds like your main power line coming into/out of the ignition switch is broken or not making contact. Look under the dash, find the connection from the steering column, look for the big red wire, that's the one you are after. They frequently corrode and lose contact which results in what you have going on. This supplies power to your car's operating systems. Most people cut this wire and bridge it past the connector. This is a lot of power going through a relatively poor connection.
Current Mopar
70 Challenger RT 440-6, 73 Cuda (under const)
05 Durango, 99 Dakota, 01 Ram 4x4, 14 2500 4X4, 10 PCP Challenger RT, 01 Viper GTS ACR, 52 B3B w/330 Desoto Hemi, 70 Hemi RR, 61 Jeep FC170
Past Mopars
9 x Challengers. AAR Cuda, 4 RR, 2 GTX, 4 Chargers, etc... (too many to list)

Offline burdar

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Re: No Power after firewall
« Reply #2 on: July 22, 2017 - 11:46:49 pm »
Pull the steering column connector apart. Make sure all connections are clean and the connections fit tight together. You can slightly squeeze the female ends together so the male end fits tight. Use some dialectic grease on the terminals before reconnecting. Do the same thing to all the bulkhead connections.

Once all connections are good, retest with your test light.


Offline w100ewd

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Re: No Power after firewall
« Reply #3 on: July 31, 2017 - 08:04:56 pm »
I've made some progress on this, but still something is very odd.  There is a splice about 12" after coming out of the first electrical box on the inside of the firewall.  There is power on the positive wire coming out of the block and when I moved around the wires I was able to get the car to start.  Once I shut off the car, there is no longer power to the positive side of the wire.  The last place I can get a test light to show power now is at the block on the firewall.  Everything on the splice looks clean and clear, however after the car starts the 1st time it looses all power.

All of the steering column connectors look clean and good.  All of the splice wires look good.  The splice itself is in tact and clean.

I'm starting to think it is in the actual wire running from the firewall block to the splice, however I cannot find corrosion on any point within the wires at all.

Any more thoughts?  You guys have been very helpful already, thank you.

Offline Bullitt-

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Re: No Power after firewall
« Reply #4 on: July 31, 2017 - 08:58:16 pm »
Tracing the RED power wire coming through #16 in the schematic to the splice I believe you refer to, there is one connection in between ..the ammeter
Could the connection there be loose?

http://www.mymopar.com/downloads/1970/70BarracudaA.JPG
http://www.mymopar.com/downloads/1970/70BarracudaB.JPG
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Offline rockymopar

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Re: No Power after firewall
« Reply #5 on: August 02, 2017 - 10:06:13 am »
I jumped my ammeter, like everyone should. I would make it near the top of the list of things to try, as it could leave you dead on the road, and possibly burn a spot on the circuit board on your dash, it doesn't happen much, but when it does....

Offline w100ewd

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Re: No Power after firewall
« Reply #6 on: August 02, 2017 - 10:54:02 pm »
I started to get after the ammeter tonight.  Looks like I have to pull the dash down to get at it.  When we put the dash in the car it sure was a lot easier without the windshield installed. 

Hopefully I will get this resolved in the next few nights.  Thanks everyone for the advice and I will let you know if it gets fixed.

Offline shadango

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Re: No Power after firewall
« Reply #7 on: August 04, 2017 - 11:27:25 am »
Looks like I have to pull the dash down to get at it.  When we put the dash in the car it sure was a lot easier without the windshield installed. 

I share your pain here, brother.   I need to pull my dash to resolve an issue with the Voltage Limiter....

I have talked myself into a stalemate -- hate to pull the dash apart in the middle of summer because its a pain in the doopah to disassemble and reassemble to test, rinse and repeat.....plus, my wiring is 40 years old...been working Ok and I hate to tinker and break stuff that aint broke yet...LOL

Hang in there and good luck!

Offline rockymopar

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Re: No Power after firewall
« Reply #8 on: August 05, 2017 - 08:59:51 am »
There has to be a way to jumper that from outside the dash. I didn't, because I needed to change a voltage regulator at the same time. Go to a website called madelectrical.com. If there is a way to jump the ammeter from outside the dash they will have it, along with other tricks that are helpful to Mopar wiring.

Offline dodj

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Re: No Power after firewall
« Reply #9 on: August 05, 2017 - 09:46:54 am »
There has to be a way to jumper that from outside the dash.
Removing the wires off the ammeter while in place is not really difficult. Lie on your back on the floor with your head mashed up against the brake pedal. Undo the large red and black from the ammeter and bolt them together, then tape. Depending on your age, you back may complain a bit. Mine never used to, but now to keep my back happy, I remove the seat for under dash work.
Disconnect the battery first.
« Last Edit: August 05, 2017 - 10:24:10 pm by dodj »
Scott
1973 Challenger  440 4 spd 
2007.5 3500 6.7 Cummins Diesel, Anarchy tuned.
Good friends don't let friends do stupid things. ........alone.

Offline Katfish

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Re: No Power after firewall
« Reply #10 on: August 05, 2017 - 09:47:11 am »
Easy way to accomplish is just add a wire from alternator to battery terminal of relay in engine compartment.
This eliminates >90% of current through firewall.

http://www.allpar.com/history/mopar/electrical.html
« Last Edit: August 05, 2017 - 09:50:46 am by Katfish »

Offline 73440

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Re: No Power after firewall
« Reply #11 on: August 05, 2017 - 12:15:12 pm »
Thank you , bolting the ammeter wires together and adding wire to relay have been added to job list.
I need to get under the dash to replace the speedo cable anyhow .
67 440
73 Barracuda w/ 68 440
65 Plymouth Fury III , I sold ,was my Nana's car till 92 yo.
51 Ford F1 239 Flathead, flipped , new cab , stolen
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Offline dodj

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Re: No Power after firewall
« Reply #12 on: August 05, 2017 - 10:26:19 pm »
Thank you , bolting the ammeter wires together and adding wire to relay have been added to job list.
Then add a voltmeter.
Scott
1973 Challenger  440 4 spd 
2007.5 3500 6.7 Cummins Diesel, Anarchy tuned.
Good friends don't let friends do stupid things. ........alone.

Offline w100ewd

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Re: No Power after firewall
« Reply #13 on: September 06, 2017 - 10:10:56 pm »
Project complete and the cuda is running and most importantly starting great again.

I was able to get to the ammeter by taking out the radio, then making a small jumper between the bolts.  There are 2 nuts on the ammeter and you need to be careful when removing them, but it there is plenty of room after removing the radio.  Putting the dash back in was pretty easy after I figured out how to make it work.

While working on this project I added a few more ground straps and wires which seems to have helped a lot as well.  These older cars seem notorious for bad grounds, so it seemed like an easy addition while under there.

Thank you for all of the advice and I'm happy to say the Cuda is back on the road.  More pictures to follow after this weekend!

Offline 70chall440

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Re: No Power after firewall
« Reply #14 on: September 06, 2017 - 11:01:34 pm »
Congrats  :2thumbs:
Current Mopar
70 Challenger RT 440-6, 73 Cuda (under const)
05 Durango, 99 Dakota, 01 Ram 4x4, 14 2500 4X4, 10 PCP Challenger RT, 01 Viper GTS ACR, 52 B3B w/330 Desoto Hemi, 70 Hemi RR, 61 Jeep FC170
Past Mopars
9 x Challengers. AAR Cuda, 4 RR, 2 GTX, 4 Chargers, etc... (too many to list)