Bought my 86Z in early summer and have really enjoyed driving it when it runs well. Have had several issues with the A/C and needed some regular maintenance. A few months back, one of my kids friends needed a jump and the friend hooked up the jumper cables backwards causing a major mess. Found a shop that works on imports and luxury sports cars and they got everything back in order but are stumped on why it loses the battery charge while driving it. They say the alternator is ok and that something is pulling extra current draining the battery while it’s driving. Any ideas?

I suspect some of what the shop thinks is wrong but............put an amp gauge on the car, that will give you at least some direction. More likely the alt is not putting out quite what it should, they can easily only partly charge too. It wouldn't hurt you to get the alt checked for 'ripple' too, the check is for possible a/c coursing through the system instead of the necessary d/c.

Put a meter on the battery, car running. It should see alternator output voltage. Start pulling fuses and have a helper watch the meter - when it stops draining, you've found your culprit.

86ZTimeMachine,

Has the battery been load tested? Autozone or the like will do this for free in the car. just to clarify....there is no drain if the car sits....only while running?

Thanks amc49 and AZhitman! I charged the battery overnight then checked it midmorning. The battery starts at 12.9V and never got over 13V even when I started the car. Over about a 35 minute period it dropped to 11.6V while just idling and no additional load except turning the lights on/off to see if they caused a major drop (they didnt and what was lost was gained back once turned off). So, you think its the alternator?

Rotorimp - brand new battery installed after my kids “incident”. Correct, no drain on the battery when it just sits, only when its running.

My first guess would be alt not charging there, that would be a whopping battery 'drain'..........dunno how hard alt is to yank but a separate alt test out of car should verify alt good/bad quick enough. You need at least 13.5 volt and on older cars, with new modern ones as much as 14 volt minimum, what my Fords output and the alt is faulty at 13.8 on those.

Dropping into 11's says alt is dead to me. Not unusual with todays' OTC chain store alts, they put out utter crap now due to 'lifetime warranties', I saw plenty of people go through 2 or 3 of them just trying to get a good one. When I worked parts I instilled an alt check at every one that went out the door; fully 20% of them were bad out of the boxes. Ridiculous.

^ This all day.