electical problem makes no sense

confused · Oct 14, 2012

Hopefully someone in the group can help me figure this one out. I have a '74 Commando and installed a Pazon ignition. I have a car battery that's on a charger providing power. It won't start. I tested the blue/white wire from the harness and I get 14.5 volts (due to the charger). Now attach the Pazon white lead to the blue/white wire and test voltage and I get 0.78 volts. ??? Shouldn't I get a reading of at least 12 volts? Now disconnect the white wire and run it straight to the battery and I get 14.5 volts which is what I would expect. I'm not understanding why I'm getting this huge voltage drop. Anyone have any ideas?

Rohan · Oct 14, 2012

How big is this battery charger ?

Unless its BIG, it won't supply enough amps to everything, and you may well see the voltage drop. The battery alone has to suuply enough herbs for any readings to be significant.

But I haven't seen your setup....

P.S. battery chargers often supply an extremely ripply power source, unless its a very fancy one. Lotsa digital stuff hate that....

Diablouph · Oct 14, 2012

Well, let's start simple, a place where I excel. Are you sure of your timing? Pull plugs, got spark?

Matt Spencer · Oct 14, 2012

Carefull you dont let all the smoke out . 8)

Might pay to isolate the area youre setting up , wireingly .As in just utilise the ignition to coils & battery . And Test .

otherwise , running a hand over the wireing lets you feel where its all warm & gooey . Before it bursts into flames .

WHERES THAT Fire Extingusher !

confused · Oct 14, 2012

Forgot to post this part: When I run the white Pazon lead directly to the battery, I will start. Just can't understand the voltage drop when wired like it's supposed to be.

Update: Disconnected the charger thinking it might be causing problems but still the same. So, I bypassed the kill switch white/blue altogether for the time being and wired in a relay to provide the 12v to the Pazon white lead and it works fine. Will wire in a kill switch later this weekend.

DogT · Oct 14, 2012

There you go. There's something wrong with that blue/white wire.

Dave
69S

Hobot · Oct 14, 2012

Kill switch is famous for this and so is broken leads inside insulation so positioning may make or break the voltage level. Possible fuse is funky only passing 14.5 when no load on it. MIght feel better and useful mechanic if checking all earth returns even if not found wrong. It ran off battery so battery good enough, just a few wires and connections keeping ya from live joys.

Torontonian · Oct 14, 2012

Wouldn't "test" anything from a battery charger. Just a strong battery only.

Diablouph · Oct 14, 2012

If you can get it to run you have solved the problem, you just don't know what it is. Now, the journey should be reasonably easy.

You will figure it out, just takes time and patience.

concours · Oct 15, 2012

OP reads "car battery with a charger on it"

Rohan · Oct 15, 2012

concours said:
OP reads "car battery with a charger on it"

Thats a complication that should be avoided ?
Either run it off the battery alone. Or the charger alone.

The voltage output out of basic battery chargers can look more like half-wave rectified AC than anything usable. Lotsa digital stuff looks at a power supply like that, and chokes.
Haven't looked at the significance of the blue and white wires here, but maybe one is masking (or correcting ?) the battery chargers influence ?

Matt Spencer · Oct 15, 2012

" Update: Disconnected the charger thinking it might be causing problems but still the same. So, I bypassed the kill switch white/blue altogether for the time being and wired in a relay to provide the 12v to the Pazon white lead and it works fine. Will wire in a kill switch later this weekend. "

Did the Italians do any COMMANDO wireing looms .

electical problem makes no sense

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