battery recharging issues

[BIGburb1989]

hello everybody,
I have my 1989 suburban, and it has some issues Im trying to work out. first off, when I drive after a period of time the vehicle just dies for no apparent reason. Ive had the alternator and starter bench tested and they passed, so the only thing i can think of is a wiring issue? please help! thanks.

[VetteVet]

Is your battery very low or dead when this happens. Check the lights and wipers or the heater. If they are strong then you have a fuel or ignition issue.

Check the alternator at the large wire with the engine running, with a volt meter and look for 14 volts.

[COS399]

My '88 R30 with a 454 used to do that, and sometimes it wouldn't start, turned out it was the pick up coil in the distributor. Good luck with it. Let us know what you find out.

[BIGburb1989]

Thanks guys. It runs fine when it sits idling, but when I drive for say 20 minutes it cuts out completely. When I check the battery is dead.

[franken]

Just random BS, but get some jumper cables.
Disconnect the big red (or not) starter cable.
Start it, drive, see if the problem goes away.
If not,
Disconnect the alt big red wire at the alt.
Start it, drive, see if the problem goes away.

The starter starts the engine. Then it's done.
The alternator provides electricity to the system. It charges the battery and runs things til the engine is stopped. If the alt doesn't charge, the battery supplies current to the ignition.

Thus, the starter and alternator are not the problem unless they aren't behaving

Assuming a charged battery (2 days on a slow charger) and 20 minutes I'd be looking at the starter.
I'd also be putting my hand on cables, connections, parts, etc. to see which if ant are hot.

[VetteVet]

Do you know what type of alternator you have. I think it is the 12 SI series. Or it might be the CS style. If it's the SI series then you can check the wires on the plug that plugs into the side.

There are 2 wires to the plug and they connect to the no.1 and no.2 terminals.
With the key off the wire to the no.1 terminal should have no voltage on it. When you turn the key on you should have 12 volts on this wire. The other wire should read 12 volts all the time key on or key off.

Here's a picture of the SI alternator.

[BIGburb1989]

I believe its the cs alternator. Its got the red cable that hooks to the battery and a wiring harness type thing that plugs into the alternator.

[BIGburb1989]

Another idea I'm throwing out there, could the trans suck power enough to kill the battery? My 700r4 won't shift into 3rd or 4th. So when I do drive it (I.e to move it to another place) it has died out on me, and its usually screaming at 5000rpm @ 50mph. Obviously I know its not good to drive but when its gotta move its gotta move.

[VetteVet]

Here is a couple of CS alternators There should be a four wire plug going into it with the initials P_L_F_S on the plug. Remove the plug and check the brown L wire for 12 volts Key on 0 volts key off. No your transmission is not related to the battery problem unless the converter clutch wiring is shorted. That would blow a fuse and the converter would not lockup.