charging system problem on 91 toy

Yes, see this page:

Are you relying on the lights to tell you it isn't charging, or a good voltmeter across the battery terminals? When I bought my '87 a few years ago, I found out the previous owner had taken out the charge and brake light bulbs because they stayed on all of the time. The alternator put out a constant 15 vdc according to my Fluke DVM. I took it to two different shops and they both said it checked okay. So we lived with it. Not too long ago the voltage went up to 15.3 vdc after replacing a 4 year old battery and I decided to replace the alternator as well. I couldn't find anything with the wiring or connectors either. Bingo, the voltage was 14.5 vdc and when I put bulbs back in everything worked okay. In the box the alternator came in was a note to sevice shops to please make sure they had the right test cable(s) I.E. there is two different type plugs on the alternators that look the same externally. According to the note this could result in erronious test results.

yeah I was using a volt meter to check if it was charging or not. Had it tested one more time. Again tested good..........put it back on the truck and its charging again!!!!!!! still not happy though because I would like to find the problem, fix the problem, and then be done with it. Could work for another 3 months or another 5 minutes for all I know.

Thanks again though for all your input ideas

Read Roger Brown's response further back in this thread - More than likely the slip-ring brushes in your alternator are wearing out and starting to fail to connect to the rotor... It will be intermittent at first, but not for very long.

Cheap to fix, once you remove the alternator and find the right replacement pieces.

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check for a short in the power wire coming from the ma8in relay or alt to the fuse panel. Short behingd the panel is fairly common and intermitent. Toyota apparantly does not care......... MLM