Darnit, My car lately has been refusing to crank, feels like a dead battery, so I replace it. Boom, cranks for a day then goes back to old problems. I read the voltage coming off the alternator with a multimeter, and it only reads like 10-11 volts, so there's the problem I think. Take the darn $150 AC Delco alternator back to Advance Auto Parts to swap it under warranty, and they insist on checking the alternator. It passes on their POS machine just fine so they refuse to warranty replace it.

I go home and put it back on, take apart and clean up the alterantor/battery wire connections, positive terminal, check grounds, etc. Cranks up first time (battery sitting all night), reading voltage at the alternator again, it is not putting out the 15 volts the in store tester said it was. Turn car off, won't crank back up, battery is mega weak tries but can't turn over engine. Obviously it is not being charged by the alternator.

Jumper it off with another car, car cranks fine. While the jumpers are connected the voltage reads 14 at the back of my alternator, yank em off, blammo 9-10 volts max. It has got to be this darn alternator, and the assclowns won't change it out, what to do?

Anything else I'm missing? Where do the wires that come out the 3 wire plug on the alternator go, and what exactly are they for? I checked them as far toward the firewall as I could reach them, and they seemed intact. Depending on what they do maybe they have a bad connection or a short somewhere, could they cause this?

This is an originally TPI car if that matters BTW, been running carbed with no computer for like 2 years. I do not recall doing anything special with the wires that plug into the back of the alternator when i converted to carb, I suppose I could be forgetting though as I can't even recall what the heck they're even for...

And this is not a hot start condition, does it while the engine is still cold too, and I already have a remote mount solenoid anyway. Jumping the car works so it can't be starter/solenoid related by my thinking...

 

Yuo should have some kind of dash light that comes on to indicate that the alt is not charging.... being a 87 model, it probably says "Choke".... does such a light come on when you turn the key to "On" with the motor not running? If not, start by replacing that bulb. The only way the alt "knows" that it's supposed to be charging, i.e. that the ignition is on, is by way of voltage received through that bulb; so if the bulb burns out, the alt will never "know" that the ignition is on.

 

Maybe no signal to turn on from ignition switch. Has to have voltage to turn regualtor on.

Kyle

 

Hmm, that's interesting.

I went out and checked, and the only places bulbs in them (or the socket for a bulb) is the Server Engine Soon light, the Seat Belt whatever light, and the Brake light. The spot for the actual Choke light has no bulb, or socket to hold a bulb. Being a TPI car I guess it didn't have that as I know I've never changed it. The Seat belt light is the only one that comes on when the ignition is on. I checked the Service Engine light and it is a working bulb, but it doesn't come on. I don't remember if it has ever come on since I ditched the computer. But I do not for the life of me recall having rigged anything so this part of the charging system would work and it's worked for a couple years or so like it sits. What else should I look at there? Is there a fuse that might be the culprit. I think I managed to pull all the fuses in the panel and didn't notice any blown. Might have missed it so if there is an actual fuse I'll double check it (most of my labels for the fuses are worn off...)

Twisted, I have a little bit of voltage, interior lights work a little, etc, and jumping it off gives me voltage to crank, (reading 13-14 with jumper cables on) but as soon as I remove the jumper cables the voltage is 10ish or so, running right off the battery and not recharging it I guess.

Sounds like something with the voltage regulator is not getting told to turn on. Let me know if anyone have any ideas what to look at there.

 

Take it in again. It might test bad. If it doesn't, bring them the car and show them that its not charging. If they still wont warranty it, ask to see the manager, get the district manager. You should check for a drain with the car shut off.. if you leave it and it drains away it may start but the alternator will have to work hard to charge it completely, and that will kill alternators. If the wiring between the alt and the battery is fine, it's got to be either something preventing the alternator from charging(it), or something killing the battery after the car is shut off(drain). Check the integrity of your battery cables.

 

Alright guys, I fixed it thanks to some of the ideas about the it being the signal to the voltage regulator. Big help, I wasn't thinking that way about it at all.

I had about two weeks ago run a new small fuse panel and seperate circuits/wires/relays for the fuel pump, fans, and the choke. In doing so I ran short of the 20 amp fuses I wanted, so I took the one out of the original fuse box that was marked for the fuel pump and fan so I could test what I was wiring. I had meant to go the store and replace that one but I had forgotten after I got more fuses, and frankly I dismissed it since it was only marked for the fan and FP both of which I was obviously completely rewiring. Apparently that fuse/circuit, it is part of whatever sends a signal to the voltage regulator, because apon noticing that fuse was still gone today double checking them, I decided to play it safe and put one in there. (thank *** I didn't dismiss it again like an idiot) Boom, that was it. Alternator is putting out a solid 14-15 on the multimeter now.

What a dumbass I am, I knew that signal ran all over the car, but I thought with the computer eliminated, fan and fuel pump all rewired seperately that it wasn't important. I hadn't driven the car all that much since removing that fuse, so I guess the original battery had enough juice to keep me going for awhile before it started dying, leading me to not suspect anything there.

doh doh doh Let this be a lesson, don't assume anything about what the wiring/fuses do... At least it only cost me a little time...