1989 electical problem

[twalker]

hey all, was wondering if anyone had suggestions or troubleshooting tips for me. brand new working alternator, brand new battery. truck wont hold a charge or stay running without being hooked up to another vehicle...bad wiring?

[fourwd1]

Don't rule out the batt or alt just because they're "new", plenty of both are bad right off the shelf.

Check all the cables, pos and neg to make sure the connections are clean and tight.
Check both ends, and not just the two battery cables, there are other ground cables, and the cable from alt to batt.

[twalker]

thanks for replying. i tested the alt and battery and they're fine. also the continuity between the female end of alt plug and battery is good. i am thinking that i will have to follow all associated wires to see corrosion or defect? all fuses and fuseable links are good. do you know how to check if all of the grounds are good?

[fourwd1]

i am thinking that i will have to follow all associated wires to see corrosion or defect? all fuses and fuseable links are good. do you know how to check if all of the grounds are good?

Physically check each end of each cable.

How did you check the batt and alt to determine they were good?
The fact that your truck won't charge and will only run when another vehicle's system is powering it would tend to indicate the alt is bad, or possibly the batt is so bad it is drawing way more than the alt can supply. A third possibility is you have some parasitic drain that is killing it, but it would have to be so much that you would more likely have a bunch of melted wiring by now.

[twalker]

i had the alt tested at a shop and i used a voltmeter on the battery. i have also tried three different operational batteries.
i wonder if this has any significance:
the fuse for the hazard, reverse and marker lights blows as soon as i replace it....

[fourwd1]

Originally Posted by twalker

i had the alt tested at a shop and i used a voltmeter on the battery. i have also tried three different operational batteries.

Those bench tests aren't always accurate, and a voltmeter isn't the best way to test a battery, but 3 other batteries is something (assuming they were fully charged at the start)

i wonder if this has any significance:
the fuse for the hazard, reverse and marker lights blows as soon as i replace it....

Yes, it does. If any fuse blows right away there is a problem. Does it blow again when you replace it?

The rev lights, inst cluster warning lights, and turn signals work off of the 15A Engine fuse

The Hazard lights use the 15A Haz-Horn fuse (radio too).

The marker lights use the 15A Tail fuse.

What about the fusible links in the engine bay fuse panel, have any of those blown?