I have a 91 LS400,. 145K miles

Recently, I've run into a problem that causes the battery to drain rapidly.

Yday, while driving but stopped at a stop light, I had a weird behavior: the wipers slowed down (it was raining), all the start-up lights came on: like engine, oil, etc on the dashboard but were dimmer than normal, and the radio began alternating between ON and OFF (even when I powered to off from on when I began observing these other things). The car then stalled and had to be jump started, twice, with same symptoms as above after the first jump. At second attempt, I kept the RPM to over 2K when idling at a stoplight but made it home without issues (approx 12 miles from incident, some freeway, some city street driving).

First indications of an electrical problem was observed about a month ago, when the engine was killed but the radio was playing (and maybe the headlights were still on since the driver door was not opened after shutting engine) -- this caused the battery to drain (in about 5 mins). I took the battery in for a checkup and I was told it was still good but needed recharging (and it was). Then the same thing happened again a week later, but a jump start got it going until the incident yday.

The car has been driven regularly between these three incidents, but generally gets only about 10-15 miles a day. It is hardly driven on weekends.

I did some searches on these forums using general terms but if anyone has pointers on more specific searches, I welcome them. Your comments appreciated.
Thanx.

 

check your battery connections and make sure everything is niceand tight, thentake you ar to an autozone and let them run another check on your battery and alternator. they do thisfor free make sure to get back to us

 

Had the same exact thing happen on my wife's 1991 LS400. Took it to the shop, they couldn't find a problem initially. Left the car running for 5 hours before they could confirm battery starting to drain due to alternator problem. Had alternator replaced, all is fixed.

 

I went and did an in-place alternator test: With car running, the battery was at 13.7V (the guy said it should be 14). When I turned on headlights, it dropped to 13.4/.5. On turning the AC on, the voltage read at 12.4V. (All this was within a couple of minutes -- not an extended test.)

The person testing said that my alternator is going bad.

This seems consistent with the previous reply.

Any suggestion on which (aftermarket) alternator to purchase?

Also, I am fairly mechanically inclined but don't have the maint manual: would I be able to replace this readily or are there some fine adjustments requiring special tools?

Thanx.

 

Can anyone provide a spec for the Alternator? It is 100A or 175A? Does it matter: there seems to be a few varieties claiming to be LS400.

Any sources besides svc dept at dealership?