faderbruce

1987 F150 Lariat XLT is driven once or twice a year and seems to have an electrical gremlin running throughout. I replaced the battery several months ago after a load test showed it needed replaced. After replacing battery it sat until last week when I started it up, looked at the dash indicator that showed it running at 12 volts. Back to auto parts store for test, shows alternator bad. Changed alternator that probably had less than 500 miles on it and fired it up. Gauge still showing about 12 volts. Took for a drive on surface streets and about 10 minutes in gauge jumped to 14-15 volts. Took it out on the highway and gauge climbed with speed until gauge showing 16-17 volts. Got off of highway and gauge returned to 14 volts but then the battery light came on, went off, came on a couple of times in less than 2 miles. Got home and thru a voltmeter on and showed 14 volts. Haven't had it out since, but hauling stones for the church this weekend and don't want a breakdown. Any suggestions? Thanks!

Steve83

Load-testing is NOT the right way to test a battery - it does damage. Click this & read the caption:


(phone app link)

Parts store employees are NOT technicians - many of them couldn't make it flipping burgers. So don't go there for diagnosis or advice.

New parts (batteries & alternators) are not always GOOD parts. They have to be tested just like old parts. Ideally, the replacement part should always pass the same test the original failed. But since you didn't test the battery or alt...

There are many things that can prevent a good battery or alternator from working properly. Most of them are described in the captions of this photo album:


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That 2G alternator is a known problem (and fire HAZARD), so if you find it needs replacement at any point, swap to the 3G:


(phone app link)