Electrical Question on a Unique

patrija · #1 (**permalink**) 02-08-2002, 09:33 PM

Hey everyone, got another question for the experts.

I'm working through a SEVERE battery drain with a local mechanic friend. He came by this evening for beers, talk, initial diagnosis, and more beers. We hope to wrap this up tomorrow. The battery will be completely dead overnight if left connected.

Here's what we found thus far using a test light in line only since he didn't bring his multimeter. Battery is in trunk with hot cable to a cutoff switch on the passenger footbox. Battery grounding looks good and the hot cutoff works correctly. The hot then goes to the solenoid, also on the passenger footbox. On the hot side of the solenoid, there are also two other heavy cables - one to the MSD box (also on the passenger footbox) and we think we've tracked the other to go back through the firewall where it joins a large bundle. This "other" one that looks like it goes through the firewall is definitely the drain - with it removed from the solenoid, the test light is dead.

We have not opened up the bundle on the other side of the firewall yet to see where it goes, but we did start pulling fuses in an attempt to kill the test light. No luck there. Any ideas????

Thanks
Jason

ERA535 · #2 (**permalink**) 02-08-2002, 09:55 PM

Trace those wires that cause the drain until you find where they are going......look for places where the insulation is off, or a wire is connecting where it shouldn't, etc.

Cobra20646 · #3 (**permalink**) 02-09-2002, 06:35 AM

Jason,

The fact that pulling all the fuses did not remove the load from the battery is a scary thought. I also assume that this anomaly just occurred and was not part of any work you recently did to the car.... right?

If the above is true, your in for a hand over hand inspection of all the wiring associated whith that feed wire you found connected to the solenoid.

And if you find that the problem is something that was not properly fused, make sure you take care of this point during the repair.

- Jim -

patrija · #4 (**permalink**) 02-09-2002, 08:38 AM

Yeah, the first thought is that the rewiring work I recently completed is the culprit. That was two parts (1) MSD 6A to Coil and (2) MSD 6A to Distributor. Since the drain is NOT on the wire from the solenoid to the MSD 6A, I think those repairs are likely safe.

This is a new problem that I'm chasing down. My guess is something vibrated loose and is grounding (not to be too obvious). I'm going to work with my friend and a multimeter and start pulling fuses again today to check the ammeter drops. I'm wondering if the light was a poor test ... either on or off.

Question on pulling the fuses - I've always tested by pulling fuses and not replacing them until the culprit is found vs. pulling and replacing them one at a time.

Thanks!

Cobra20646 · #5 (**permalink**) 02-09-2002, 07:06 PM

Jason,

The test light placed in series with one of the battery cables is a good and safe way to check for current flow. Since the test light only requires a tiny bit of current to illuminate the bulb, it is a poor way to determine the amount of current flow, or the severity of a short circuit or other circuit fault.

A multimeter installed in place of the test light will give you a better handle on how much current is flowing, and while you go about trouble shooting the wiring harness and or pulling fuses, any changes in the amount of current flow will be noticed immediately.

Pulling each fuse (and leaving it out) one at a time will allow you to see the current draw for each fuse. Do this test with the ignition switch on, and again with the ignition off. Ideally, with the ignition off, you shouldn't have any current flow at all. If you have a radio with memory, or an electric clock, or any other device that requires a constant supply of 12 volts, than you must determine if this current demand is "normal" or too excessive.

Also, check the alternator and regulator. The hot lead from the alternator usually connects directly to the junction terminal on the solenoid, but maybe yours is connected somewhere else, and is causing this drain.

These problems can make you pull your hair out, but hang in there and try to take a logical and systematic approach to locating your problem. And don't arbitrarily assume that any recent rework is not to be suspected. Go back and double check what you did to see that you did it according to the directions..... you did read the directions didn't you?

Good luck

- Jim -

poorboy · #6 (**permalink**) 02-09-2002, 08:15 PM

I think on a Unique the feed to the alt. comes from the amp gauge in the dash. I would check the alt. first.

Poorboy

JimsGems · #7 (**permalink**) 02-09-2002, 08:39 PM

When all else fails give Maurice a call, he will likely have the answer, or can give you a educated WAG! Hey! What could it hurt.

Wiring can break internal to the wire coating but that just causes Grimmie's and intermittent problems, I have had a bad solenoid with a direct short to ground once upon a time. Re-Check your recent work and verify all wires are landed correctly and all the connectors are properly crimped and the conductivity verified. Good luck, these are the tough ones.

patrija · #8 (**permalink**) 02-11-2002, 05:59 AM

Unfortunately we did not get to touch the car this week - major "honey do" lists for both me and my friend. Since I'm now at work and am racking my brain on this one, here's another recap of Friday's testing.

Solenoid has two heavy side connections and two smaller connections on top. Per the ProDesign book, I'm fairly sure the two small top connections are the ignition and starter? One of the heavy sides appears to be the ground? The other heavy side has three connections: (1) battery POS from the cutoff switch, (2) MSD 6A wire, and (3) the "culprit" wire in question that appears to go back through the firewall. I think the "culprit" wire is red/black ... but I am going by memory and could be wrong. The wire does have a connection in it about 6 inches off the solenoid and changes to a grey wire, so tracking it is a bit of a challenge.

Our testing on Friday night started with hooking a test light in line at the POS battery terminal. All testing was done with ignition in the off position. Here's the approach we took:
1) We disconnected everything on the solenoid - no test light.
2) Added the battery cable back - no test light.
3) Added the ground(?) back - no test light.
4) Added the two top wires back (starter and ignition?) one at a time - no test light.
5) Added the "culprit" wire back - test light.
6) Removed the "culprit" wire - no test light.
7) Added the MSD 6A wire back - no test light.
8) Added the "culprit" wire back again - test light

At this point, we think we have identified the "culprit" wire as the only drain. To test, we again removed everything from the solenoid and only hooked up the "culprit" wire and the test light came on. It was getting late, so we did a quick follow on the wire and it looks like it went through the firewall. Hopefully this week we'll get some evenings in working on it.

Jim: Thanks for the thoughts. We're definitely going to tackle this with a multimeter. Directions ... blasphemy!!

Poorboy: I don't have the ProDesign guide with me at work, but based on what I read last night I'm wondering if the "culprit" wire could be to the Ammeter with a connection back to the alternator. If so, that might pinpoint it to the Alternator?

poorboy · #9 (**permalink**) 02-11-2002, 01:25 PM

Jason;
The connections on the solenoid are on one side batt. feed,MSD,Amp meter& fuse box. Other side, power to starter. Ground should go from solenoid mounting bracket to frame. The amp meter wire goes to one side of the amp meter, out of the other of amp meter goes to alt. To check alt. just disconect batt. wire from alt. Poorboy

patrija · #10 (**permalink**) 02-11-2002, 05:56 PM

PROGRESS ... tracked down the battery drain!

I'm going to use Unique's ProDesign wiring specifications to describe. The wire off the solenoid POS side turned out to be wire #27 that runs to the Ammeter ACC connection. Both the ACC and BATT connections on the Ammeter were hot, indicating electrical flow. I then disconnected wires: 41 (AMMETER BATT to FUSEBLOCK), 25 (AMMETER BATT to IGNITION), and 39 (AMMETER BATT to ALTERNATOR BAT). The culprit was 100% wire 39 with no other drains.

OK, I understand electrics by am a self-admitted poor mechanic. I tracked it to the alternator ... now what?

Thanks!
Jason

PS. Gotta give great thanks to Unique and Bruce Botti - cleanest markings and wire arrangements I've ever seen on an electrical system.

Poorboy: You got it right on!

Bob Putnam · #11 (**permalink**) 02-12-2002, 04:17 AM

It's very likely that the alternator has a bad diode. Either rebuild or replace.

patrija · #12 (**permalink**) 02-13-2002, 04:42 PM

Bob: Thanks!

Quick follow-up question. It's been suggested that there's a possibility it could also be a bad voltage regulator rather than the alternator. Does that make sense? I can't figure out how a bad regulator would pull a current and drain the battery.

Thanks again!
Jason

Bob Putnam · #13 (**permalink**) 02-14-2002, 03:45 AM

Most harnesses power the regulator through the ignition switch so
it wouldn't show up as a switch-off current draw unless there was
backflow through the stator connection.

poorboy · #14 (**permalink**) 02-14-2002, 06:22 AM

Bob, Jason;
Unique uses a aftermarket regulator mounted on the back of the alt., one wire hookup. Battery wire is hot all the time.

Poorboy

patrija · #15 (**permalink**) 02-14-2002, 06:31 AM

Bob: Thanks!

Poorboy - Thanks! Actually I have an external regulator mounted on the inside passenger side fender. Mine's a 98, maybe that's something that changed. I sure can't see room behind the alternator though.

patrija · #16 (**permalink**) 02-14-2002, 12:31 PM

OK ... I don't understand this one, but I think the drain is fixed. I was doing some more experimenting around the alternator and disconnected the wiring harness connection to the external voltage regulator ... low and behold the drain dropped to zero. So, new regulator installed and no drain showing on the battery. Don't understand it, but maybe not arguing either!