Aaargh! Electronics for the electrically challenged?
 

My car was doing okay and then my charging system just stopped. It's driving me crazy. I've gone through all the wiring and it's all okay. Everything is wired according to the diagrams and all the fusable links seem okay in the harness, etc. Even any questionable connections were re-done if I didn't like them. The battery and alternator checked out okay at 3 different shops. I've scuffed and cleaned every ground surface and every ground strap and wire. Still nothing. :willy:

I can have a fully charged battery and put the multimeter to it. It'll read good (about 12.70) at rest. I can start the car and it drops to about 12.0 and slowly goes down as the car sits there running. As long as the fan doesn't turn on I can unhook the positive post and the car will continue to run. The idle quality diminishes greatly but it'll still run (until fuel in the bowls runs out -electric pump). But if any other accessory is turned on, or the fan kicks on, it's simply more than the alternator can handle and the car dies (still with the positive lead off). It's like the alternator is running but not enough. The idle changes because the MSD and coil aren't getting enough juice, thus no zap in the plugs. So now I've got fouled plugs to boot. :willy:

I've got a 140 amp alternator wired in with a Painless High-Amp alternator harness. The big Maxi-Fuse is still good. It's internally regulated and the old regulator harness is bypassed per Painless instructions. Because it had previously tested okay and was running fine for hundreds of miles, it seems like something just popped.

Driving the car results in no juice getting to the coil and it runs poorly. The fuel pressure dwindles away as the pump slows down, too. I've driven it about 75 miles like this, in one trip, at night, and it never killed the battery enough to kill the car. The lights were dim and the fuel pressure was getting scary-low but the car never just stopped. :eek:

I've swapped in a different horn-relay/junction block, a new remote solenoid, all the fuses look good, etc. With the hot lead off the battery the multimeter reads only about 7.4 volts from the wire terminal.

Another thing I noticed, which may be okay, is at the ignition-hot wire from the harness to the alternator pigtail: The white (?) wire from the plug in the alternator is wired to the ignition-hot wire from the stock external regulator plug. (As per Painless instructions). Just testing with a test light I noticed that the light is pretty bright/hot before the two wires are connected. Once connected the current in that line only dimly lights the test light. I've tested it enough to verify it's not the connection from the tester. It's just an anomoly I noted. I don't know if this is a clue or not.

Any ideas? What other tests would you use to diagnose this?

Ther should only be 2 wires at the alternator, on eis the battery charge line (the big one by itself), the other is the exciter line to turn on the regulator, most guys (including GM) wire that back to the ignition switch. I just run it right back to that that battery lug with a short 2-3 inch jumper lead. If you have B+ at the exciter trigger and only battery voltage at the charge lug than the alternator is junk.



PS, disconnecting the battery while the car is running is a bad idea and a really bad idea if you are running a PCM.

Now I'm going really nuts! I may call Painless in the morning. I can't even find the kit that I bought on their site. I was wanting to link to a picture of the instructions.

The pigtail connector has the "exciter" wire run to the Ignition switched hot lead from the original regulator plug.

The other pigtail wire is run directly to the hot post on the back of the alternator, as you mentioned Dennis.

This is where it gets fun: There are actually TWO other large gauge hot wires running from the back of the alternator (so 3 total connectors on one post). One of the hot wires goes directly to the hot alternator lead from the original harness. The other wire goes to one side of their "Maxi-Fuse". The other side of the fuse in turn goes to the battery. Essentially, there are two hot wires now, from the back of the alternator. The additional one is linked with a big fuse and goes directly to a B+ while the other goes to the battery via the stock harness. Make sense?

I thought the installation was funky when I did it, but it all checked out, and it ran like a champ for a while. It's also directly per their diagrams and even speaking to them on the phone to verify. So I'm not really leaning toward the design as the issue. Their wiring kit is totally different now, though, and I wonder if they have decided that was a bad design or something.

You might read over this article by Mark Hamilton about remote voltage sensing. Although many cars run with the voltage sensing wire ran directly to the output on the alternator and yours ran that way previously you may want to change that. What is the voltage at the charging lug on the back of the alternator with the engine running? Compare that reading with the voltage at a main electrical junction and the battery. You might also check the voltage readings at a higher RPM to see how this affects the readings.

Just my .02.
Deron

I'd put good money down that you have a bad alternator, it should work fine the way you have it wired (albeit the extra wire isn't really nesessary).

Does the charging lug voltage match (within a few tenths of as volt) that of the battery post? If so, replace the alternator...they aren't new forever.

I'll check the lug today.

I'm with you though- my bet is the alternator. But 3 different places have checked it and given the okay. I just don't believe them. I have a theory that it is putting out something so it's showing to be good, but it's just not putting out enough.

Now that all the wires are pulled out and exposed, I think I'm going to re-route and wire everything again since I can do it much cleaner than I did originally. Maybe I'll find something then.

Anyone else have ideas? I'll lett you guys know what comes of this.

ny

updates?
 

Any update on the problem Y-TRY?

I hate electrical gremlins :mad:

Goodluck

Deron

I was over there today and re-wired and routed most of the system. Still no big red arrow saying "Here I Am", though. I opted to just remove the secondary Painless jumper wires.

My battery is here at home recharging since each attempt and test drains it down after a while.

When the battery is back up I'll take it over. I'm also going to verify the grounds by using jumper cables on the negative post and the body/frame/engine just in case the grounds I have are insufficient. Currently the battery is grounded to the body, the body to the frame and frame to engine. It may be as simple as adding another strap from body to engine or any other combination.

If none of that works I'm buying some marshmallows and rolling the car off a cliff, baking the 'mallows in the flames. :D

There needs to be a positive ground either to the frame or engine. Grounding the main battery feed through the sheetmetal is NO GOOD. The sheetmetal can't handle that amount of load. If you want to ground the body directly off the battery that is fine but you need 2 cables, 1 for the body and 1 for either the engine or frame. You can ground the engine through the frame or vice-versa if you want.

nathan i know it maybe some little stupid thing but you know how you can get under drive pulleys for Alt. and water pump to help with power i was looking at those Black Mountain pulleys you have and they say underdrive on the ad. Could it be that they are making your Alt spin too slow to charge everything? just a thought.