Fuddling electrical failure 72 convertible

7173Mustangs.com

Help Support 7173Mustangs.com:

Joined
Oct 6, 2021
Messages
110
Reaction score
21
Location
Near Tampa, FL, 33511
My Car
1972 Base Convertible 302
I have all good fuses and electricity is going from one side of each fuse terminal to the other. The wipers, turn signals, radio and pretty much everything but the headlights and brake lights are dead. My son, who uses it as a daily driver, says that when the fuel gauge works, the other electrical components will work. When we had it apart to install the clutch for the T5 conversion, I put a new voltage converter in the dash just because it was accessible. I also put in new flashers. I am pretty sure the fuel gauge would be affected by that if it is malfunctioning. Could it also affect anything else? It does not make sense that the wipers would be affected, but he says they run, along with the turn signal and radio, when the fuel gauge works. It appears that if the volts are higher, stuff works. The alternator and voltage regulator are new. The same problem was manifesting itself with the old voltage regulator. The battery is new. A faulty new one was replaced by Autozone. The starter had been replaced with an O'Reilly one which appeared to be suffering from heat soaking and they replaced it. The new one is wrapped with a heat shield. They checked the charging system and said it is good. The headlights are now on a separate relay, so the headlight switch isn't carrying the amps for the lights. We did that when upgrading the headlights. Any thoughts would be appreciated.
 
Joined
Sep 8, 2018
Messages
1,800
Reaction score
730
Location
Ross, Ohio
My Car
71 Sportsroof Bright Red.

I have all good fuses and electricity is going from one side of each fuse terminal to the other. The wipers, turn signals, radio and pretty much everything but the headlights and brake lights are dead. My son, who uses it as a daily driver, says that when the fuel gauge works, the other electrical components will work. When we had it apart to install the clutch for the T5 conversion, I put a new voltage converter in the dash just because it was accessible. I also put in new flashers. I am pretty sure the fuel gauge would be affected by that if it is malfunctioning. Could it also affect anything else? It does not make sense that the wipers would be affected, but he says they run, along with the turn signal and radio, when the fuel gauge works. It appears that if the volts are higher, stuff works. The alternator and voltage regulator are new. The same problem was manifesting itself with the old voltage regulator. The battery is new. A faulty new one was replaced by Autozone. The starter had been replaced with an O'Reilly one which appeared to be suffering from heat soaking and they replaced it. The new one is wrapped with a heat shield. They checked the charging system and said it is good. The headlights are now on a separate relay, so the headlight switch isn't carrying the amps for the lights. We did that when upgrading the headlights. Any thoughts would be appreciated.
+1 with Hemi. The gauges are on the instrument voltage regulator at 6v. The wipers, radio, turn signals are all 12v. If you are getting power on both sides of the fuse block then I would start checking for ground issues. One quick way to check would be with the wiper motor. Take a wire direct from the negative post at the battery and run it to the ground strap on the wiper motor. If it runs then you have a grounding issue. If not, then perhaps it could be that the fuse block harness connection halves are not making good contact.
 
Last edited:
Joined
Oct 6, 2021
Messages
110
Reaction score
21
Location
Near Tampa, FL, 33511
My Car
1972 Base Convertible 302
Thanks both! There were no problems with this stuff before replacing the IVR, but we had the engine out for a rebuild and did a T5 conversion with the American Powertrain kit. Don't get me started on that. At any rate, a lot of stuff was disconnected and reconnected. Everything works when the voltage is above 13.2 or so and then stops working when the voltage goes lower. It does appear that the IVR is sensitive to input voltage, but it makes no sense that wipers and radio stop working. We did put in HiPo LED bulbs with the recommending HiPo flashers and it makes some sense that this stuff could be more voltage sensitive than what was there before.

I will reinvestigate the grounds. The battery cables might be suspect and we are replacing them with the high draw kit from West Coast Classic Cougar. The ones on the car were probably put on by the consignment shop when they were concealing flaws. They are all blue which is really wrong for a lot of reasons, primarily, of course, because they confuse people when hooking stuff up.
 
Joined
Aug 28, 2011
Messages
706
Reaction score
73
Location
Spirit Lake, Id
My Car
1971 Boss 351, 1969 Fairlane 500 Conv., 1965 Sunbeam Tiger
Also check the ground strap that runs from the rear of the engine block to the firewall. On a '72, it's a flat, braided copper wire if I recall correctly. I forgot to reinstall it on a previous car when I did an engine rebuild and it caused all kinds of similar problems.
 
Joined
Oct 6, 2021
Messages
110
Reaction score
21
Location
Near Tampa, FL, 33511
My Car
1972 Base Convertible 302
Thanks and ah ha, we do not have that. The engine was not original and perhaps the people who dropped it in didn't replace it as I don't recall seeing it when we pulled it but that was about a year ago and memory is somewhat faint. If anyone has a photo of it, I would love to see it.

I just cleaned connections at the battery terminal and the grounds on the voltage regulator and tried it. When it started the first time, the volts only went up to 12.75 which is about what the battery was at rest. Nothing worked. I shut it down and pondered things, and then started it again. This time, the volts went to 13.92 which seems reasonable after starting and everything worked. While I think the wipers should work at 12.75, I am beginning to thing there is some intermittent issue with the charging system. The voltage regulator was replaced recently and the alternator was replaced before we did the engine rebuild. I realize that a lot of these parts come from China and QC is often questionable. The alternator is a Powermaster which I thought was a better quality brand. The voltage regulator is the AutoZone brand.
 

Hemikiller

Well-known member
Staff member
7173 Mustang Supporter Member
Moderator
Joined
Jul 12, 2010
Messages
3,987
Reaction score
1,295
Location
Killingworth, CT
My Car
71 Mach 1
71 XR-7 coupe
71 Country Squire
65 coupe
Also check the ground strap that runs from the rear of the engine block to the firewall. On a '72, it's a flat, braided copper wire if I recall correctly. I forgot to reinstall it on a previous car when I did an engine rebuild and it caused all kinds of similar problems.

That's not a factory Ford 71-73 item. The chassis ground on these cars is the strap integrated into the ground cable.


71ground.jpg
 
Joined
Oct 6, 2021
Messages
110
Reaction score
21
Location
Near Tampa, FL, 33511
My Car
1972 Base Convertible 302
Thanks! The cable on the car does not have the clip in the middle. Do you know what the clip is secured to? Or does the clip go to the block and the ring terminal someplace else? I don't see the clip on the one I ordered, so I will fabricate one to add to the wiring.
 
Joined
Apr 14, 2019
Messages
262
Reaction score
69
Location
center Valley , pa 18034
My Car
72 Vert 351C White
Thanks and ah ha, we do not have that. The engine was not original and perhaps the people who dropped it in didn't replace it as I don't recall seeing it when we pulled it but that was about a year ago and memory is somewhat faint. If anyone has a photo of it, I would love to see it.

I just cleaned connections at the battery terminal and the grounds on the voltage regulator and tried it. When it started the first time, the volts only went up to 12.75 which is about what the battery was at rest. Nothing worked. I shut it down and pondered things, and then started it again. This time, the volts went to 13.92 which seems reasonable after starting and everything worked. While I think the wipers should work at 12.75, I am beginning to thing there is some intermittent issue with the charging system. The voltage regulator was replaced recently and the alternator was replaced before we did the engine rebuild. I realize that a lot of these parts come from China and QC is often questionable. The alternator is a Powermaster which I thought was a better quality brand. The voltage regulator is the AutoZone brand.
 
Joined
May 22, 2022
Messages
33
Reaction score
34
My Car
1973 Mustang Convertible
Also check the ground strap that runs from the rear of the engine block to the firewall. On a '72, it's a flat, braided copper wire if I recall correctly. I forgot to reinstall it on a previous car when I did an engine rebuild and it caused all kinds of similar problems.
I am having some electrical issues with my ‘73. Does this grounding strap apply to the 73 as well?
-Julie
 
Joined
Dec 28, 2014
Messages
2,773
Reaction score
383
Location
Washington Twp. Mi
My Car
1972 Mach 1 Q Code
I am having some electrical issues with my ‘73. Does this grounding strap apply to the 73 as well?
-Julie
There was no ground strap from the back of the block to the firewall installed at the factory. But I added one and I also added one from the front of the block to the front clip. I do have the correct battery cable with the ground clip, but was having some weird electrical problems. After I added the two ground straps I haven’t had any issues since.
 
Joined
Aug 28, 2011
Messages
706
Reaction score
73
Location
Spirit Lake, Id
My Car
1971 Boss 351, 1969 Fairlane 500 Conv., 1965 Sunbeam Tiger
According to Hemikiller, the ground strap my car had was not original. Basically, there has to be a ground between the battery and the chassis at some point. If your negative cable just goes to the engine, the chassis isn't grounded well enough.
 
Joined
Oct 6, 2021
Messages
110
Reaction score
21
Location
Near Tampa, FL, 33511
My Car
1972 Base Convertible 302
The battery cable we have has a small wire on the terminal that attaches to the negative post on the battery. This wire, maybe 14-16 gauge, grounds at the solenoid. Our car suffers from the overtightened at some point sheet metal screw hole problem which probably means inconsistent contact. I am going to put a bolt through that hole to make it more securely connected, but I think adding a better ground cable would be wise.

So far, we seem to be having fewer issues now that I wire brushed the ground cable ends and the attachment points, but time will tell. I am guessing that an erratic ground could also cause the voltage regulator to not step up the voltage properly which has been part of the issue. I also used some Rail Zip, a model railroad product that cleans contacts and helps maintain them. There are a bunch of similar products on the market, but this stuff used to save a lot expensive photo equipment back in my newspaper career, so I still have it around. One of my guys was a model railroader as well as photographer and clued me in on it.

The IVR clearly wants more volts to operate properly. This is the modern, electronic Daniel Carpenter one we got from NPD. There are actually two of them in the car, one for the center dash instruments and the original for the cluster in front of the steering wheel. Both was about 13 volts to operate properly and we were having issues with the alternator not coming up as it should all the time. I think that this had been a problem before the engine rebuild, but a new alternator appeared to fix it. I now wonder if the problem was the grounds as pointed out by the first two answers, THANKS AGAIN!, all along.

Again, thanks to all.
 

InjectedMach

Well-known member
Joined
Sep 7, 2011
Messages
97
Reaction score
10
Location
Springville, AL
My Car
1972 Mach1
2011 Grand Sport Corvette
2008 Toyota Tundra Crewmax
I do all kinds of upgrades and engine swaps and there are some points that can't be skipped being proper grounding and supply voltage.
The store bought molded terminal battery cables are garbage and you can in 50% of them simply pull the conductor out of the terminal. Buy good metal terminals and crimp and solder them on. We also ground from the frame rail to the block on the driver side, from the head to the framerail on the driver side but not under the same bolt on the rail, from the battery to the engine block on passenger side, from block to rail on the passenger side and off the battery to the apron just to be redundant. The positive cable goes to the battery and startersolenoid and solenoid to starter motor with one more to the alt from the harness. Clean all these terminals of rust and paint before applying dielectric grease under all connections. Don't overlook the ignition switch and pigtail. In these cars the entire electrical load runs through, not around the switch itself. We also use 2/0 welding cable for primary conductors. We face challenges sure but not from iffy electrical supply and unststable power.
Hope this was helpful.
 

Hemikiller

Well-known member
Staff member
7173 Mustang Supporter Member
Moderator
Joined
Jul 12, 2010
Messages
3,987
Reaction score
1,295
Location
Killingworth, CT
My Car
71 Mach 1
71 XR-7 coupe
71 Country Squire
65 coupe
Sounds like you're headed in the right direction. Cleaning up the mounts (ground connections) for the solenoid and voltage regulator can only improve their operation. Get some stainless star lock washers and place them on top of and below the mounting brackets, Amazon has some bulk assortments for cheap.


Like InjectedMach, I used welding cable for my battery leads and starter cables, with cable lugs and heat shrink from McMaster Carr. I also welded in a bolt into the apron as a ground lug. Another point to cover is that a lot of the parts store and "reproduction" regulators are absolute trash. I like scavenge OE Ford units from salvage yards, along with OE starter solenoids if I can find them. This rusty POS on my 71 has been on there since 2006, and the battery in the pic was bought in 2008 and is still going strong. I cleaned everything up last year and put a cover over the OE Motorcraft electronic unit.


1663693685195.png



1663693909567.jpeg
 

Latest posts

Top