Help Please Damn Car

[lone73]

Ok forget brown, it's white in your case...

Thank you lone for all your doing for me I owe you one bud.

One Bud??? Whaddya' mean? You owe me a whole 6 pack !! Hahaha. Just messin' with ya'...


I was thinking earlier how useful a pic or two would be.

Now pull the plug off and measure the resistance between that white wire and the turn sig fuse w/key off. Whaddya' get ?

This is interesting, I can tell from the schematics that the wire is brown for '73, '75 & 77. Yours is white. I wonder if someone has done some creative wiring hidden by that fresh looking black tape near the end of the harness. You might want to peel it back a ways and look for a bubba'd, hand twisted together (read, no solder) splice hidden inside that harness.

If you find a splice you'll need to solder it to make a good connection, use heat shrink over the splice and use a heat gun (or a hair dryer) to shrink it. Don't tape it, that is ugly, unprofessional and will not last. Heat shrink, if you're not familiar is available from Home Depot, Lowes, Radio Shack, etc... and comes in a variety of sizes and colors.

talk later

lone73

 

[VRGSVET]

Who wired up your stereo? Are the amplifiers wired directly to the battery? Hopefully they're not spliced into the alternator wiring. Either way, if your amplifiers are pulling enough current, which it sounds like they are, that can be enough to burn up your alternator repeatedly. For a juiced up stereo, you should buy a higher amperage alternator. I've burned up a couple alternators on my Chevy pickup, just running two 200w amps.

As for the short problem, and I agree, this sounds like two separate problems: It's impossible to tell for sure without being there, but I think there is a constant short. Now, I could be wrong, I've proved myself wrong many times shooting wires. But, it could be two wires shorted together, not to ground. When both circuits are activated, one wire acts as ground, overloading the current and popping the fuse. Or it may be a wire shorted to ground somewhere, that is just barely making contact. It may only pull 10 or 12 amps. Once you activate something else on that circuit, the total current draw jumps up over 15 amps and blows the fuse. Like I said, it's frustrating without seeing a schematic. On the other hand, lone73 may be absolutely correct, it may be simply intermittant. In which case, a wire is probably rubbing against metal somewhere and just needs the right bump or vibration to cause it to short. In either case, the key is to find the short.

To find a short you need an ohmmeter, preferrably digital so you don't need to worry about polarity. You need to check wires in question from one end to ground. The key here is to isolate the circuit. To do this, you need to unplug connectors, remove fuses, light bulbs, whatever, so all you have is wiring attached to nothing. Put one meter lead on the end of a wire and the other to bare metal, preferably something attached to the frame. The meter should read greater than 100 megaohms or O/L if it is not shorted. If it's shorted it will read less than 10 ohms, more like 1 or 2. But, even if it reads anywhere from 10 to a few hundred, it may be shorted. The problem with shooting wires on cars is that several circuits share the same power wiring at the fuse box and it's extremely difficult to isolate the circuit. If something checks bad, make sure you're not reading through another circuit. The other problem is, even if you do find a wire that shoots bad, it is probably spliced into another circuit somewhere up or down stream and you won't know which leg of wiring the short is in. But, it will at least narrow the problem down. Once you find which wire is shorted, you will have to physically inspect the entire length of wire for bare wire. In fact, if it's an intermittant short, this is really the only way to find the problem. Unless, you get lucky and shoot the wires and they just happen to be shorted when you do. Bottom line, you need to find wiring that has been pinched, crushed, or chafed, so that the insulation is gone and allows bare wire to touch anything metal. To do that, you have two options; start tracing wire bundles from end to end, taking things apart along the way to get access. Or, take it to a professional. Sorry I'm not much help. Good luck.

 

[Red76Vette]

Lone73,

Okay your absolutely right it was brown someone patched some white wire in using a one of those wire crimps. Is that causing the problem do you think? But I am getting 10 ohms resistance is that good or bad? If I figure this out I owe you a whole case man Ha-ha.

Thanks,
Chuck

 

[Red76Vette]

VRGSVET
I did the wiring of the amps and the it is directly to the battery not through the alternator.

Thanks,
Chuck

 

[lone73]

Solder that splice...

Chuck,

10 Ohms is a high reading for a straight piece of wire. I'd start by soldering that connection as described above. Use some heat shrink on it. Your dad probably knows how to do a good job on it if he's an electrician. Get him to help you.

I don't think the splice is the major charging problem but I can't see it. It's definitely one problem IMHO, I hate crimp-on splices. Those crimp connectors are just a good place to grow green funk anyway and it needs to go.

When you're done check out the resistance between the turn signal fuse and ground as described above and get back to me.

There's a connector in the circuit downstream of the fuse, we can look at that later..

good luck

lone73

 

[Red76Vette]

Oh I can solder much better than he can I can do it. Ill try it and see what kind of resistance I get thanks for that idea.

Thanks,
Chuck

 

[Red76Vette]

I soldered and shrink wrapped it. Still 10.4 ohms hummm what could it be?

Chuck

 

[lone73]

Terminal resistance

You're probably reading the resistance between the tips of the leads and their points of contact. The ignition switch is also in the loop, there could be a little bit of resistance there. You did a good thing by eliminating that crimp connector, it'll save you some heartache later even if it doesn't cure anything today. Put the meter leads directly together and see what resistance you get. You can deduct that reading from anything you read in a circuit.

What did you get from the turn signal fuse to ground?

 

[Red76Vette]

It’s only like .01 or less it is a fluke good quality DVM. So it’s like 10.39 or so. Well I guess ill have to figure out what else it could be? Should I get a reading from the other fuses from that same brown wire and what does that wire do? Supply power to the fuse box or just the lights on that particular circuit I don’t know my 1967 passenger car service manual doesn’t have a wiring schematic. Is there one online somewhere I could look at or do I need to buy one? Well thanks again for all you do and have done for me.

I got .798 to ground

Thanks,
Chuck

 

[lone73]

.798 ohms???

Chuck,

I'm sure the brown wire is just a sense line from the rest of the electrical system to the alt. It applies the voltage it "sees" from the fuse block or tail lights on that terminal on the back of the alternator. The '75 has that "sense" wire connecting to the turn sig fuse THRU the ignition switch. The '77 schematic shows the wire tying into to the hot side of the turn signal, tail and stop lights but NOT the B/U lights. That 10 ohms might be looking thru one or more of the tail light bulbs. Let me think about that one a while longer.

Again. I don't have a '76 schematic and I'm having to interpolate and guesstimate my way between my '75 map and the '77 ( I wish I could borrow your young eyes ) but I'm very concerned about the .798 ohms ( thats less than one ohm you're saying, right? ) that you get from the turn sig fuse to ground. That sounds very near a short to me. You did take the fuse out and measure between the downstream side (opposite the power side of the fuse) and ground right?

I'm gonna' try and e-mail you...

lone73

 

[Red76Vette]

No I didn’t take out the fuse, I don’t know what side it should be on maybe ill just do both sides and get back to you. Tomorrow morning I am going on a business trip for the weekend ill be back on Tuesday. I can’t thank you enough for all your help, it is greatly appreciated. You can e-mail me at chucksciano854@hotmail.com

Thanks,
Chuck