.75v drop through bulkhead??

[EL5DEMON340]

Noticed on my 68 RR voltage to the battery at hot idle is at 14.8 give or take .10, when i measure the voltage at the battery not running with key on.. its about 12.35v and coming back out at the blue with tracer going to the VR its about 11.55v. the ign switch is new and my amp meter in dash is still hooked up and terminals are tight. Where should i start to look? is this to much of a drop?

 

[67Dart273]

That is "plenty." A more accurate way of doing this is by measuring the drop directly--you don't have to do any math.

Turn on the key to "run," engine off, if you have a points ignition make sure the points are closed. Do this by measuring the coil positive to ground. If it's close to battery, they're open. Bump the engine until the voltage falls low, anywhere from 4-8V, far below 12.

Then simply stick one probe directly onto the battery positive, the other on your dark blue "ignition run" (or ign terminal of the regulator) and read the drop directly.

This drop, by the way, ADDS to your charging voltage when running.

Most likely culprit is the bulkhead connector itself, so dig up a diagram and probe the engine side/ interior side of the bulkhead connector and see if that shows a drop. If not, next most likely is either the connector on the ignition switch, or the switch itself.

Don't forget to check the FEED to the ignition switch, AS IT TOO comes into the bulkhead and is subject to drop.

This is EXACTLY why so many of us advocate simply swallowing your Mopar pride and eliminate the connector by whatever means.

In some cases the so called "ammeter bypass" helps. In mine it did not. After the ammeter was bypassed the "dark blue" connector ALONE had a one volt drop from battery to ignition.

 

[crackedback]

Check where the big black wire from the alternator travels through the bulkhead. Probe both sides of that junction. It's a notorious area for problems.

 

[Demon 408]

...This is EXACTLY why so many of us advocate simply swallowing your Mopar pride and eliminate the connector by whatever means.

In some cases the so called "ammeter bypass" helps. In mine it did not. After the ammeter was bypassed the "dark blue" connector ALONE had a one volt drop from battery to ignition.

I agree. But I kept my bulkhead connector and rewired my charging circuit with larger wire and bypassed the bulk head connector by running wire through grommet directly to dash. I also eliminated the ammeter and had it converted to a voltmeter.

See my upgrades here: http://www.forabodiesonly.com/mopar/showthread.php?t=73437

 

[EL5DEMON340]

is it possible that its the alt, i just did some checking and removed the green wire from the alt unfortunately the insulator fell off and grounded to the alt body, and now i think my alt is fried it does not charge, switched out the V/R and still no charge, But now i'm getting only a 1/4v through the bulkhead to the v/r.

 

[67Dart273]

No, as your first post indicated, if those conditions are as you say, you have too much drop.

Measure like this, and here is what you are measuring: The drop from the battery, fuse link, through the bulkhead, through the ammeter circuit, through the ign switch connector, the switch, and back out it's connector, and back OUT the bulkhead on the dark blue

Turn the key on, engine off. Put one probe on the battery + post, and the other on your dark blue on the ballast. If you have points, make sure the points are closed (drawing current.) The resultant reading will show you directly the drop in this circuit.

Also note that this drop WILL CAUSE overcharging by that amount, IE a .5V drop in this circuit will "tell" the regulator it is 1/2 V low, so it ramps up the alternator another 1/2 volt

 

[EL5DEMON340]

No, as your first post indicated, if those conditions are as you say, you have too much drop.

Measure like this, and here is what you are measuring: The drop from the battery, fuse link, through the bulkhead, through the ammeter circuit, through the ign switch connector, the switch, and back out it's connector, and back OUT the bulkhead on the dark blue

Turn the key on, engine off. Put one probe on the battery + post, and the other on your dark blue on the ballast. If you have points, make sure the points are closed (drawing current.) The resultant reading will show you directly the drop in this circuit.

Also note that this drop WILL CAUSE overcharging by that amount, IE a .5V drop in this circuit will "tell" the regulator it is 1/2 V low, so it ramps up the alternator another 1/2 volt

Thanks 67, That's how i checked it, only i had my neg leed on the - post and was probing with my + leed, from - bat to fusable link i had 12.35 with key on (electronic ign), then to dark blue on ballast i got 12.15, bat was at 12.40 with key on. before i grounded the green to case of the alt i would get about a .75v to .85v drop. i'll go back out today to check from + post. May order a new harness from YO just for the h**l of it they are running a 30% off sale and it would cost $96 shipped, mine looks ok but it is 43yo and is showing a few insulation cracks & hardness.