Hello everyone

Hoping to get some electrical help on my 72

It has a V8 in it but will not pass any power

No buzzing of the fuelpump
No dash lights
No radio
no horn

nothing


I pulled the ignition switch and tested it

It was open until I turned the key and ohmed to almost 0 ohms
When I released it open circuit

Checked all wires in harness good

Ohmed out every fuse in the panel below dash as well as a few in the rear of the car.

Checked the ground strap (now a battery Cable)

At first I was not getting continuity between the tranny bolt and the body

Cleaned up the connection to the tranny as well as to the body ohms out to 2 ohms

Checked the battery 12.5 volts

Ohmed from neg terminal to chassis ground ohmed to 2-3 ohms

It was running fine yesterday until i turned on the headlights while staring it

then it died and I havent been able to get it to crank

Any help would be appreciated

thanks

MIke

Do the lights come on with ignition off?

Do you have any electrical power on anything?

How about the 4-way flashers? They work with or without key in.

Did you clean the battery terminals?

How about the ground strap from battery negative to ground? Is it tight?

What is the battery voltage from positive terminal to chassis ground (not batt neg)?

No lights at all

No power at all

4-way flashers do not work

re-cleaned battery terminals tight

battery neg to chassis ground 12.3 volts

re tightened ground strap to chassis and tranny

no power on fusebox under dash

3 vdc when key is off
0vdc when key is on

thanks for your help

You mean battery POS to ground?

If battery NEG to chassis ground then there is no connection between battery NEG and chassis. What condition is the negative cable between battery and the chassis bolt above the battery?

If nothing works, then it's likely the battery or wiring, not your ignition switch or the engine ground strap.

Try this test:

Turn lights or 4-ways on.

Measure voltage across the TERMINALS of the battery, not the clamps. Touch the battery terminals.

Then measure voltage from POS terminal to POS battery clamp.
Then measure voltage from NEG terminal to NEG battery clamp.

Here we're trying to find where the battery voltage starts and where it ends since it's not making it to any components.

Yes you are correct

Positive teminal to chassis is 12.3 volts

I turned on 4-ways
No lights as before

0 volts bet pos terminal to pos clamp
0 volts from neg terminal to neg clamp

OK, sounds like the battery terminals are tight.

No voltage at the fuse panel? The first 3 fuses from the center of the car outward are constant 12V. If not 12V, then some wiring issue is at play.

How do the small wires look coming off the POS terminal? These wires go to the fuse panel.

Before you go behind the fuse panel, disconnect the battery NEG terminal. Do NOT move the fuse panel with battery connected.

Behind the fuse panel is a POS terminal block on the side of the chassis. Make sure this is tight.

With the fuse panel down, make sure no connections touch anything. Connect NEG terminal to battery. Test the positive terminal block behind the fuse panel from terminal block to chassis. Should be 12V.

Do you still have the OEM positive clamp w/ 3-4 ~10ga wires and a large 2ga cable to starter. IIRC, one of those wires goes to the fuse panel and the other to the ignition switch. Find that wire and check it. If you do have 12v then put some load on it and see if you lose the 12v. I've had some bad connections give me a good reading until they get a little load on them.

Thanks

I will re-check the smaller wires coming off the POS terminal at the battery.
I will then disconnect the NEG terminal and drop the fuse panel and make the check you recommend

thanks for your help.

Mike

I have some really heavy gauge wires going back to the starter

I put my pos terminal from my multi meter onto the pos on the starter and sparks flew.

I will send a pic of what I have

thanks

Mike

Sounds like 2 of the 4 wires connected to the positive battery terminal are disconnected. 2 go to the alternator circuit and 2 go to the fuse panel/ignition switch.

I think you may be onto something

i will trace 4 wires back and make sure the connections are tight

Hello Everyone

Thanks for all the help.

I pulled the NEG off the battery and dropped the fuse panel
Behind it was a terminal block with the positive lead attached just as I was told.
I only measured 3.2 VDC when the key was off and 0 when it was on.

Puzzled I once again checked the fuses this time in the back of the car.

I found 1 fuse that was a 30 amp.
It tested good but was melted.

I had to pull it out with pliers and thus destroyed it.

Went to the auto parts store and picked up a new fuse.

Took some emery paper to the contacts.

Plugged her in and what do you know I have power and she is running again!

You are the most helpful group of folks I know.

Thanks very much!


Mike