1987 Chevy suburban not charging problem

[KennyB49221]

Hello so I ran a 10g wire from the back of the alt+ to the pos. of the battery and the truck is still not charging. Im thinking the wires from the harness that plug into the alternator are maybe bad, Do those tell the alternator to charge?if not what is it for? Also there is a wire from the alternator + that goes to an ignition relay or junction box on the firewall that looks like it was repaired what is that?excite wire? How much do u think it would cost to get the whole truck rewired? Your input will be greatly appreciated.

Added: Someone thinks i have the wrong alternator on the truck, and that a one wire alternator should be on it. There is a connector next to the alternator that isnt connected to anything. I dont know what its for. right now the alternator has the black connector connected in the back then the wire to the pos. battery and a fusible wire to the junct. box. I dont know what the connector is thats coming out of the harness and not hook up to anything.

[rcbildr]

The alternators I've dealt with on my 82, 84, and 85 Suburban have 3 connection points. There is a post on the back of the alternator and 2 spade terminals on the side....the side connection has a plug with 2 wires going to it. The terminals on the side are part of the internal voltage regulator and tell the alternator when to charge. I'm not sure when GM went to the one wire alternators, but I would think they would keep the 87 the same as the others up til the body style change in 91. If there is a NAPA close by take your alternator there and see if it is the right one. Also, buy a Haynes manual. It has a lot of good info and with it you should be able to trace out your wiring.

I'm not sure on this, but I think you can buy a new harness for just the engine compartment...LMC may have it. When I completely rewired my 71 chevy truck I bought a painless harness for something like $350 thru JC whitney...not sure of the price for the newer Suburban.

Can you take pics of what you are working with?

After reading your post again, I think that connector on the harness needs to be plugged in to the alternator....look for a space on the side that has two spade terminals. Hope this helps.

[tom coop]

500 for a painless wiring harness for newer burb

[KennyB49221]

Update....... I bought a new self exciting one wire alternator (I think its a delco 12 Si) and now the truck is charging, Thank God. Its giving out about 14.7 volts with the headlights on so I think thats fine. Thanks everyone for the help.