I think there's a short in my new engine harness... how to track down...?

[MEK-Dangerfield]

Looks like my less-than-year-old alternator is the culprit.

Disconnected the alt's main lead and the draw seems to have gone away.

Any idea what could have caused it to fail so soon? I'd hate to buy another one just to have it get toasted, too.

Keep in mind, there are 2 wires for the field of the alternator in your wiring harness. Were these connected when you discovered the current draw was from there? If you connect the two field wires, and leave the main lead off, and there is no current draw, then it sounds like you have found the problem. I just don't know what could have happened. 


  Mike

[ViperMan]

I kinda skimmed posts real quick so my apologies if this is duplicate information, but the fuse block is the best way to check for shorts.

Remove all the fuses, then, using an ohmmeter, put one lead against a solid ground, and use the other terminal against each each of each fuse terminal in the fuse block.  You should have infinite resistance (meaning no connection whatsoever) at each terminal.  If you suddenly see any amount of resistance, then you have a short.  I used this technique when I rewired my dash and engine bay to make sure I had no problems.

Also, 4-5 ohms of resistance is perfect.  If you touch your leads together you should read 4-5 ohms of resistance.  I haven't seen a meter yet that doesn't do that.

Jeff

[Grec]

Yeah, Mike. The two field leads were on. Every wire was connected except the alt's main lean when I got the draw to disappear.

I'm scratching my head too, though.

By-the-way, nice tip Jeff. I'm sure I'll have a need for it in the future. :-)

[Grec]

Just had a thought... are my alternator's field leads hooked up right?

I'm 99% sure they are, but just to double-check, from left to right looking down at the alt:

Black main lead - green field lead - blue field lead.

[ViperMan]

No that's right.  But even if they were switched it wouldn't cause an extra draw.  The main terminal and field terminals never actually come in any contact with each other.

Jeff

[Grec]

Gotcha.

Just checking. :-)

[PlumCrazy]

Why are you not talking with M&H about this problem?  If you would have called them, they would have most likely modified the harness for free or at a minimal cost and it would have still been a new uncut and warrantied harness.  I would suggest you call Tom at M&H in the morning and discuss this problem you are having, he will be able to walk you through a logical, step by step path to resolve the problem.  Tom's number is 562 926-9552 x201.

[Grec]

Well, I had all the tools and materials to modify the harness correctly so I went for it.

Turns out my work was fine, as verified by continuity and resistance testing on every wire and that the problem lies elsewhere.

Honestly, I never even thought to have them do it... still, I like doing that kind of work so I would have probably done it myself anyway. :-)

[moper]

Glad you found it. Alternators can fail without notice, and new doesnt always mean good. Was yours a reman unit? Places that deal in mainly retail (AutoZone, O'Reileys, etc) will usually stock the cheapest rebuilts. It's because they are the cheapest rebuilts. You should always shop for auto parts where most garages do...Your local jobber stores. Like Napas, Car Quests, etc. They have to have parts that stay good. Otherwise the garages would hang them...lol. If your's is a dated original, talk to your local garages. See who is a good local rebuilder. They can usually do nice work too.

[Grec]

Yeah, it was a remanufactured unit, but I'm starting to lean towards my ignition as being the real culprit in this.

Before I changed my engine harness, I had only been getting around 6 volts to the positive side of my coil... about 4 to few.

This wire ends at the ignition and everything in between looked fine. No corrosion, frayed wiring, nothing.

Coincidentally, the alternator's main lead runs through the firewall to a junction where one of the branches goes to... the ignition.

My theory, for now, is that there's a bad connection in my ignition switch that is causing both these problems.

Too bad I have to get a new tool to pull my crush can to find out!

[moper]

Use your tester, and get the voltage from both sides of the ballast resistor (72-up have the 4 prong deals...) You will have two inputs, and two outputs on it., The two inputs should have bettery voltage at them with the key in the run position and start position. One leg of the ballast resistor has a higher resistance than the other. This is the "run" leg of it. The "start" side has less resistance in it.  When you tunr the key, the "start" leg should have close to battery voltage present (disconnect the fender relay for these tests so the engine can't turn over). WHne you release the kay and it springs back to the "run" position, the other leg of the resistor should show about 9 volts on the output side. If it shows less, and the battery voltage is right on the input side, it's the resistor that may be incorrect, and you may find it hard to get the right one. If the batery voltage is low on the input side, there is a problem between the battery and the ignition switch, or between the ignition switch and the ballast. It's fairly coommon to see the brown wire going to the ign switch to be melted a bit, and the connectors in the plugs to be melted to, because a lot of guy use the key to turn the engine over for far too long.

[Grec]

Yep.

I've already determined that the voltage loss is occouring before it gets to the resistor, which is, of course, how I would have expected it to be.

God forbid that it be something that $10 and a single bolt could fix.

No. Now I have to tear apart my steering column.

[MEK-Dangerfield]

It might not be your steering column. Being old wires and all, anything could be getting old, or the connection at the bulkhead might be corroded, or melted.

OK, I tell you a deep dark secret here. I have a low voltage to the ballast resistor problem too. My problem comes about(I believe), because some genious(sarcasm) mounted the electronic ignition module to the inner fender on my passenger's side. Up front too. That causes a much longer run for the voltage to get to the resistor, coil, and ignition box, since they are all mounted up front. This causes a voltage drop of 1 volt. This stinkin' 1 volt loss will not let me start the car under 40*. Sooo, I ran a wire from the starter relay to the underside of my dash, and connected it to a toggle switch. The other side of the switch goes back out to the "input' side of the ballast resistor. I just flick on that toggle switch before I try to start the car, and it fires everytime, in all temps.  Do not try this at home kids. 


  Mike