In the final stages of re-assembly after flares & paint. I wired up the alt exactly the way it was when I took it out, and has always been, but I'm not showing any voltage change at the output pole whether the car is running or not. I'm running the Renegade serpentine set up with AC on a 350.

I replaced the alt while I had the engine out with a higher amp unit because I've had charging "issues" with the car literally since I got it, (battery would slowly run down over time, and I've have to charge it), so I thought this might fix that. I've had the new one out and bench tested, and it's putting out 13.8v on the test stand. I'm using an alt for a 93 Buick, and historically it's only had the heavy wire from the output to the start, which then goes to the batt, and the lead on the plug which lights the idiot on the dash. When I start the car now, the idiot light goes out, but I'm only showing like 11.8-ish volts at the pole, and that doesn't change whether car on or not. Guy who built alt for me says as far as he knows, you must have 12v to the "red wire on the plug", which was never connected to anything before. After jumping that to 12v, no change. 11.7-ish volts, and car dies if I disconnect batt.

Electrical is always my weak suit. Any ideas? HEEELLLP ME. . . .

If 2 alternators act the same, the problem is with wiring or the battery itself. Have you load tested the battery?

If the car dies when you disconnect the battery, it's either the alt, or the wiring from the alt that is the issue...

First thing I would do is verify the new alt is actually charging.
It could be a bad rebuild.

Oops, my bad, as Rick has pointed out, it's been bench tested as per your original post...

Carry on...

If the bench test showed 13.8 the alternator is working. Here's a couple things I would check.

Disconnect the wire from the alternator from both ends and make a continuity test. Check to see the wire is not shorted someplace or maybe the wire you THINK your connecting actually is the wire that is connected to your starter terminal.

Try that and report back first then we can talk about the next step.

I've had charging "issues" with the car literally since I got it, (battery would slowly run down over time, and I've have to charge it), so I thought this might fix that.


The alternator is NOT your problem. If the battery is losing voltage no alternator you put on the car is going to fix the base problem. You have a short somewhere else in the car that needs to be found and fixed first. The only thing you need to worry about in the alternator dept, is making certain all of your connections on the alt, batt, grounds etc are good, solid and clean. Bad/dirty connections can cause your charging, and possibly your drain issues

You need to pull all the fuses.
Put a voltmeter between the red batt cable and the pos battery pole.
The voltage should read zero.
Then put one fuse in at a time and see if voltage is flowing for each circuit.
If you have a circuit with voltage running through it then figure out why.
Possibly a short, possibly the clock,radio, amplifier. Something maybe wired on continuously. Possibly the power to the distributor.
If all circuits check out, then it maybe a bad diode in the alternator.
How old is your battery? Have you load tested it?
Also, Some alternators have to be "excited" before they will put out voltage.
Hence the idiot light, or a resistor somewhere.
IF your idiot light is an LED it wont do the job.

Good advice above...

Small hijack, but could you post some pictures of your car? I've been wondering how it turned out.

Check your ground strap at the trans+trunk floor too. I'm running an extra ground strap off of the engine block as well.
Marty

Simple pic for 3-wire GM alternator here:

http://www.hotrodders.com/forum/attachment...achmentid=36187

It's quite normal for the car to die when you pull the battery even if the alternator is working OK, as the output from the alternator isn't smoothed and the battery plays a critical role in stabilizing the 12v rail.

Slow drain on the battery won't affect charging; you should hunt that issue separately.

As suggested above, check your alternator-to-battery cables. You should have battery-to-starter and battery-to-alternator cables assuming a normal 914 layout; make sure the crimps on the wire at each end are solid and clean; if you can jiggle the wire or it looks corroded consider a replacement. Suitable cables will be cheap at your FLAPS.

If you can, check the voltage across the cable (+ve on the alternator terminal, -ve on the battery terminal), it should be very close to zero.

Depending on the kind of bench test, it may still be toast. But start with wire and connectors.

yeah you hae to excite the alternator, I think you jump the two terminals at the top and run the engine to 2500 rpm.....it should start putting out like a cheap hooker!

The old ground connections on these cars really need to be cleaned up. I also use an extra ground strap.

Sorry guys, I should have been more clear on the prior problem. It would lose charge while sitting. Hell, I would leave it sit from November thru April, and she`s good to go every year. But when I drove it, it would slowly lose volts.Not so fast that it was not charging at all, but it seemed to me that the alt maybe couldn't keep up with the demand of the 2 pullers and 1 pusher fan, and I was afraid to run the A\C and the the cooling fans, or I'd have starting problems for sure.

I've got the alt wired exactly as shown in Mike's diagram above. Note that it never had the jumper before, but it does now. Rick, I'm pretty sure my output wire has to be good, because I get he same reading at the alt pole with the car off as I do at the battery, and that's the only route the juice could be using to get there. My wiring goes alternator to starter, starter to battery. My grounds are "fresh washed baby's butt" clean, but I may ground 1 of the mounting bolts just to be super sure. I guess I also haven't run the rpms up when I've tested either. I'll take run at those first chance I get.

One thing that is puzzling me is that the alt light on the dash functions as it should if the alt is working. If the light is on when I turn the key, but goes out after a few seconds, doesn't that mean the alternator is functioning? And if so, why can't I measure a voltage change at the output post of the alternator????

And Jim, I will get some pics up. It really looks amazing. My guy took a long time, but his attention to detail is insane, and the result has been worth the wait. I'll try to get some pics up today.

Shouldn't need 3 fans . . .

Please do not disconnect the battery when the engine is running. In automotive test standards such as ISO 7637-2 (pulse 5a) this is called "load dump" and can cause damage to the alternator and other electronics in the automobile.

It is likely you did not have a load dump since your alternator is not working in the car.

Measure voltages at the output of the alternator to CHASSIS ground; not the engine. When running the voltage should be > 13V.

Bruce, the 3 fans are the standard Renegade set up for a car with A/C, and as hot as she can get with the air on on a really hot day in traffic, I don't think it's overkill.

I'm not a big fan of the "pull the battery cable" alternator test either Jerry, but no worries on the electronics here. I'm running decidedly cutting edge 1965 engine management tech, so the only electronics in jeopardy on my car would be the radio.

Sorry Jim. I don't have as many decent pics as I thought I did, and i couldn't steal as many off Steve's site as I though I could. I'll take some soon. Here she is at the begining of the rebuild process.
Click to view attachment

Oh. I did mine before Renegade sold the cooling kit. I just use two puller fans. They are tripped on by either the A/C or thermostat as needed.

I often wondered it the alternator belt being under driven since it's off the harmonic balancer would make a big difference it heaving traffic driving, but I never had a problem. I also have a much smaller intake area for the air. I found that the larger area of opening for the exit helps create a lower pressure to draw the air out and creates less turbulence in the trunk. Fans don't run too often.

Sorry haven't red everything but since it seems your using the 914 harness and alt light in the dash I would first stab a test light to the wire at the alt connected to the wire connected to the IP alt light. Maybe the resistance / amperage draw is just not to the liking of the CS alternator. Not much to test IMO, At most 3 wires BAT. IGN. and the one I mentioned above.
Set me straight if not reading everything puts my size 12 in my mouth LOL

Just my 2 cents voltage doesnt flow current does. Voltage is pressure and current is flow. Are you telling him to use an ammeter in series with the red wire and pos post?

Well this is embarrassing, but here goes:

My alternator wasn't working correctly because you have to route the belt in a way that it will actually turn the pulley with some authority, and apparently going REALLY near the pulley ain't good enough. Who knew.

Since I got the car, I've had issues with the belt requiring WAY too much tension to get the whole thing put together, and I thought I had a genius moment which solved the problem. Not so much.

In my defense, besides being an idiot, there is literally only 1" of clearance between the firewall and the belt path, and it looked like the alt was all good with my new plan. Turned out the belt actually was about a standard pubic hair above the pulley, and juuuuust touched the pulley enough to make the idiot light go out, but not enough to generate juice.

God as my witness, I thought my belt plan would fly.

On the plus side, 14.4 volts all day long now. Thanks for the help boys.

Why is your screen name aircooledboy?

Ouch. I've been type cast.

Because only one of my current 914s is watered, the other is fully air reliant for cooling. Because I've owned at least one 914 or another nearly continuously for the last 30 years or so, and only the most recent one is a water pumper. Because I eat a lot of fiber, which causes a lot of gas, which results in a certain amount of heat disipation when I let one fly. . . .

Alright, maybe TMI on that last one.

I've been a 914 guy a LONG time. I just don't need much help with the stock ones. It's the 350 with all its customized shiat that often leaves me scratching my head trying to figure out the basic theory of some component or system so I can trouble shoot it. Like a modified wiring harness for a '98 Buick adapted to a '78 350 sitting in '73 Porsche. Sometimes I forget to look at the forest before I start examining each individual tree.