65 Conver electrical issue

twoseater · 05-20-07, 02:56 PM

Hi all - I have 1 amp drain on the battery which equals dead battery in a couple days. I've read the threads regarding electical issues (very helpful) but haven't quite got it nailed.

With all fuses removed, I still have the load, which tells me its not a fused circuit.
If I remove the left hand connector on the firewall I still have load which tells me its not the lights.

If I remove the right hand connector on the firewall then the load goes away (No amp drawn is seen on the amp meter which is connected between the positive terminal on the battery and the positive battery cable.)

So I believe I've isolated it to the right hand connector wiring but am unsure how to proceed further.

What I think I know:

Its not the Voltage regulator (swapped it)
Its not the Alternator (had alternator tested).

Could this still be a horn relay issue? Looks like in the wiring diagram indicates it is connected to the horn switch. Anyway I can rule out the horn relay?

Any advice on what/how to check next?

Vetsvette2002 · 05-20-07, 10:51 PM

Re-check for a bad alternator. Using your DVM, disconnect the alternator and check for draw.
Take the glove box lamp out and see if the darw goes away. This can aslo be done in your darkened garage to see if any of tehcourtesy lights are on.

Post what you find and we can go from there

twoseater · 05-21-07, 07:00 PM

Hey Vetsvette2002 - thanks for the reply!

With the alternator disconnected (meaning White and Blue connector pulled) no draw on the battery. These are the same leads that connect to the voltage regulator and then onto the Firewall.

I did pull the glove box and right door bulb - still have the 1 amp load. I was pretty sure they were on a fused circuit and all fuses were pulled and the load persisted. I'll double check to make sure the glove box and doors are on the courtesy circuit.

My next step will be to make a harness so I can "Break" each wire from the firewall to fuse box to hopefully isolate it to a specific wire. Looks like the battery gauge must be connected with an "in" and "out" from the gauge.

Really appreaciate the help as I'm stumped at this point.

Vetsvette2002 · 05-21-07, 07:19 PM

You just diagnosed your problem. When you disconnect the alternator, the draw goes away. Somewhere in the alt. there is a short to ground. Replace it

twoseater · 05-21-07, 07:54 PM

Hmmmm. The load also goes away if I pull the right hand (as seen from drivers seat) wire harness off the firewall with the alternator connected. I took this to mean the short was further ahead of that connector.

Is there anyway I can test the alternator myself? I took it to AutoZone and they bench tested it several times with a machine where they hook it up and run it. Perhaps that test doesn't check for shorts and just tests voltage output?

I just want to be sure before I invest in a alternator. The disconnection of the firewall harness and the load going away has me confused.

I'm also guessing that my '80 vet has the alternator with the voltage regulator built in so I can't just do a swap test with that car...

Vetsvette2002 · 05-22-07, 08:47 AM

Your previous post said that "with the alt the load goes away".
Disconnect the pos. battery wire to isolate and prevent arcing
Set yiour meter to ohms and put one probe on a good ground or the neg bat terminal preferably and the other to the following three locations:
1. alternator case should be 0 ohms
with the alt two wire connector removed;
2. left terminal in alt should be infinity ohms
3. right terminal in alt should be infinity ohms

You problem sounds identical to one I had in my 67 several years ago

A new alt at AZ should only be about $45 and a new VR is about $15. If your current alt and VR are the originals DO NOT GET RID OF IT.

garth64 · 05-22-07, 01:45 PM

To just isolate the alternator, disconnect the lead from the horn relay to the alternator(bat terminal); if the draw stops it is probably due to a shorted diode in the rectifier bridge in the alternator.

twoseater · 05-22-07, 10:01 PM

Thanks Guys - problem solved!! Turns out my ignition switch is hosed. Off and accessory are too close to call - There is no positive stop between them. When the key is in the off position it is in the accessory position now....if I bump it a little I can then feel it go to the off position.

I doubled checked by fidgeting with the key and I can reproduce this at will. When accessory is on there is a 1amp load - what that load is I don't know.(It certainly not a light as my nothing is showing up in the dark).

Thanks you - I really appreciate the help and responses.