Help! just replaced starter, now alternator circuit broken.

[ajackson]

I am clueless on this one, any help would be appreciated.

First the car:
77 911 with 3.2

The lead up:
I have been having off and on troubles with the car starting lately, so I eventually ordered a new hi-torque starter from pp. Pretty easy install: figure out how to get at a bolt at a wierd angle and it was done. Car started great, drove it around locally for a few days just fine. Saturday rolled around and I took off at 6am for the CFoS, only to make it about 5 miles before the car completely died.

The problem:
Had it towed back to my house courtesy of Hagarty and found that the battery was completely dead. Did a few tests and realized that the alternator was not charging the car while it was on. Checked a few obvious things, replaced the alternator warning light, checked that the wires to the starter were on good, but no luck. I haven't taken apart the fan cover to actually look at the alternator yet. Since it happened right when I replaced my starter I am thinking that has to do with it. Anyone have any insights other than to go through the alternator circuit, piece by piece?

[scottb]

I'm not an electrical expert by any means, so take this with a huge grain of salt.

Have you checked the various grounds on the car both for corrosion and tightness? I've read that a bad ground can do unexpected things to the car's electrical system.

Whatever the problem, good luck fixing it. Let us know what you conclude.

[Jim Sims]

I will conjecture you failed to reconnect the medium sized red colored wire that also attaches to the same stud of the starter as the large black power cable. Running the engine with this red wire disconnected may have damaged the diodes in the alternator in addition to disabling the charging circuit. If you're lucky the diodes survived. Good luck, Jim

[scottb]

Now, Jim Sims *is* an expert on these things. Hopefully he's steered you in the right direction. You may have to pull the alternator and have it checked at a local Autozone or rebuilder.

[Joe Bob]

Fully charge battery, put meter on it....should read 12.5v....start car, red light in dash should be ON, then off when started, put meter on battery again...should read 12.5-13 volts at idle, 13.5-14v+ at 2500 rpms.

Less volts or more...bad alternator and/or regulator....if less than 12.5 before start up...bad battery.

[ajackson]

I've done a few tests, so maybe I can help you guys help point me in the right direction.

I fully charged and tested the battery -- everything is good there. While running, the voltage does not go up at all, telling me that the battery is good, but the alternator is not charging the battery while running.

As for the red wire on the starter, I did connect it and rechecked that everything was hooked up properly.

[Superman]

Originally posted by Jim Sims
I will conjecture you failed to reconnect the medium sized red colored wire that also attaches to the same stud of the starter as the large black power cable. Running the engine with this red wire disconnected may have damaged the diodes in the alternator in addition to disabling the charging circuit. If you're lucky the diodes survived. Good luck, Jim

Yep, this is my guess too. There is a fat wire to the starter from the battery, and another fat wire to the starter from the alternator. If they are not both connected at the starter, the juice from the alternator cannot get to the battery. On my starter there are these two herky cables, and there are two other yellow wires, much smaller. Look again.

[ajackson]

I'll check again tonight, but I did connect both the fat black and the fat red wires to the starter (cleaned and secured with a nut). I only had one smaller yellow wire on a tab type connection.

[Joe Bob]

When mine didn't charge the wire to the alt light was disconnected....light wasn't coming opn before start.

[Superman]

My hazy recollection is that the two fat cables are screwed down onto the same post on the starter. There is probably another large post, and if you connected the alternator cable there, it would only charge during starting, and not even then because the alternator wouldn't be spinning.

[ajackson]

I have the two cables connected to the same post. Is it possible that there are two posts and I hooked them up to the wrong one? I'll have to dig up some pictures of the hi-torque starter...

[rcecale]

Yep, just changed mine a couple of weeks ago (and it still turns right over EVERY time ) And both of the big fat wires had to connected to the same terminal. As far as I recollect, there was only one "big" terminal for them to connect to.

You shouldn't have to, but you may want to take a piece of 100 grit or so sand paper and scuff the terminals of the fat wires. BE SURE TO DISCONNECT THAT BATTERY FIRST!!!

Since you've charged the battery, will the car start up and run again? If so, start her up and while she;s running, disconnect the battery. If she dies, you can be pretty sure the altenator is bad. AFAIK.

Oh, and speaking of the battery, try cleaning the the posts and terminals. Make sure you have a good connection there as well. wouldn't hurt.

Well, there's MY complete $.02 worth.

Randy

[JTL]

A couple of years ago after reinstalling a rebuilt starter I noticed the volt meter reading slowly dropping. I was forced to take a detour through a scummy area due to heavy highway traffic. I barely made it to 'the right side of the tracks' when the car died. Volt meter indicated about 8 volts at the time. After getting some help from AAA I checked the connections and found I had connected the alternator wire to the other extra post on the solenoid. The started worked fine but the battery would not charge. Lucky for me to have had a voltmeter. So - check your wires.

Jt
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