Alternator won't Alternate

[87Lowrider]

Alright,

On my '87 SWB, I installed the '76 454 in and got it running last week. Having problems now with the charging system. I used the original wire to the alternator and the original alternator from the '87. It worked fine in November when I dismantled the system and pulled the 350. Now, it won't charge the battery.

Again, I'm wondering if there is something in the harness that keeps the alternator from charging just as the oil pressue switch kept the fuel pump from running until I hooked up the switch?

Thanks in advance!!

Ken

[old Rusty C10]

easiest thing to do is take your alternator to a parts store like auto zone and have them bench test it it is possible that it got ruined sitting

[87Lowrider]

Thanks Bob,

I'll do that tomorrow.. I always liked that name, "BOB", either way you spell it, it's correct.

If that doesn't work, I'll be back!

[AceX]

Easy name to spell when you're hammered...

Back on the subject, If you can, get a higher output unit. You may not need the extra amps now, but what happens when you want to add electric fans? better/more lights? power doors? a stereo?

It's worth the extra couple bucks. As soon as my dad's '06 is out of warranty, it's getting a 180amp unit.

[S10Fan]

Wiring, gotta love it. LOL.

When I stuffed the V8 in my S truck I upgraded to a 130 amp unit, also went with a 1 wire. AceX is correct. I figured the aftermarket electric pump, stereo, and (at the time) electric fans could use the juice.

[old Rusty C10]

i agree with the other posters, if ya can get one with higher amps may as well so you can run more stuff

[454HO]

The '87 alternator should be a high output, probably a 12si. Check here

http://www.madelectrical.com/electri...elcoremy.shtml

to identify it. If so, it should have one connector with two flat terminals.

Term #1 is the Field and should be the brown wire that goes to the charge indicator lamp in the instrument cluster. This wire energizes the field at start-up and if it is not connected the alternator will not put out any power unless you rev the motor past 2000 rpm or so. Then it should 'self-excite' and start charging. Does the charge indicator lamp light up if the key is in Run position but the engine not running?

Term #2 is for remote Sensing and needs to be +12V. It usually connects to the distribution block up on the firewall to the right of the distributor, or it can connect to the battery lug on the starter motor. You can also hook it directly to the Bat terminal on the back of the alternator but that defeats the purpose of remote voltage sensing and effectively make it a one-wire alternator.

[joeymarkgraf]

Technically speaking, it could still "alternate", but not work...

[Pyrotechnic]

I agree, get a 12si if you don't already have one. I gave them a 10si that still worked but had a stripped bolt hole for a 12si core and they didn't really care or know the difference.

I believe the sure fire way to get the high amp 12si is to say you have a 84 Camaro 305 High Output with A/C.

[87Lowrider]

Originally Posted by 454HO

The '87 alternator should be a high output, probably a 12si. Check here

Term #2 is for remote Sensing and needs to be +12V. It usually connects to the distribution block up on the firewall to the right of the distributor, or it can connect to the battery lug on the starter motor. You can also hook it directly to the Bat terminal on the back of the alternator but that defeats the purpose of remote voltage sensing and effectively make it a one-wire alternator.

Greg,

Mine is a 12si with the flat 2 term connector, It has switched +12v. The red wire coming off the other termminal and connecting to the terminal on the rear and has no power.

I have elec windows, doors, small-mid size stereo and elec fan so big amps I like. I took the alt off last night and gonna check it at parts store today.

Thanks for the info!

Kenny

[87Lowrider]

Well... Autozone says the alternator is GOOD!

So, there must be something else in the wiring stopping the system from charging... I've checked the fuses, all ok. Could it be the battery?

[454HO]

Originally Posted by 87Lowrider

Mine is a 12si with the flat 2 term connector, It has switched +12v. The red wire coming off the other termminal and connecting to the terminal on the rear and has no power.

Not sure I follow.

Term #1 should be connected to a switched 12V source. Usually it is wired thru a light bulb on the dash board. If that light bulb does not illuminate when the key is first turned to the Run position, then the alternator will not work. Please verify that Term #1 has 12V when the key is in Run without engine running.

Term #2 is the sense wire. It should be connected to a constant 12V source. Common places are the juctiontion block, the starter motor, or the BAT terminal on the back of the alternator. Some sources I've read say this wire is optional, ie does not need to be connected to anything.

BAT on the back of the alternator is the charge wire and should be a #10 or larger. It should go straight to the battery + terminal.

With the wire loom and the small size of this pic, it's hard to see what you've got going on here. Do you have any close-up shots?

[87Lowrider]

Greg,

You know that V8 commercial? That's how I feel.

I looked at my '86 Jimmy again and saw the wire going to the battery from the BAT lug.

On the '87, when I tore it down in November, I forgot that there was a wire from the battery, but luckily I took pictures, I just looked back at them again and found a blurred one that shows the hot wire going towards the battery from the BAT lug. It also showed the wire from TERM #2 going to the BAT lug.



I'll make up a #10 wire from the BAT lug to the Battery and fire it up. Thanks for the wake up call!!


Kenny

[87Lowrider]

UPDATE: Works like a charm!!

Greg: U DA MAN!


Kenny

[454HO]

Glad you got it working!!