Quick question about alternators and 1jz

[jaze]

Hey fellas my 1jz e36 BMW has been running for a good week and then one day the lights starts dimming, the radio turns off and the car starts idling rough and the car shuts off and won't start due to a dead battery.

I jump the car, and it idles for like 3 minutes then the lights dim and it eventually dies. The third time I rev up and everything brightens and dims with the idle.

I disconnect the battery while the car is on and it stays on if I keep it at 1600ish rpm. But that happens even if the battery is connected

Here are some theories and tell me if I'm
Barking up the wrong tree here.
1. Voltage regulator or the smaller brush isn't spinning right which boils down to buying a new alternator.

2. I have no ac so I got a chevy s10 belt since I has seen it somewhere that it fit. There is 3 notches on the motor and the tensioner is lined up almost with the one all the one to the right. Is the belt not tensioned properly by the tensioner so the alt doesn't spin fast enough?

3. My car has been idling like at 550-600 rpms, I find it really low. Could that be messing with the alt? Somebody told me 1j's idle low but damn, that's low.

I wanted to get an opinion here so I'm not blindly spending money. Any help or input you guys have would be greatly appreciated, thanks.

 

[hvyman]

Disconnecting the battery with the engine running is a no no.

easier way would be to get a volt meter and check the output of the alternator. Sounds like its bad tho.

 

[dmvirus]

get a digital voltmeter, attach it directly to the battery if it reads just above 12v when the engine is running there is something wrong with your alternator. since it dims maybe a diode in your rectifier is fried. if the ic is damaged the alternator wont charge at all. youd have to change any of those parts.

if it reads 13v at below 800rpm and above 14v at 1000rpm your battery is damaged. to my experience. id say your battery is damaged

 

[jaze]

Thanks guYs, I do have a multimeter and at idle which is at 600ish it's at 12.6-12.3v then starts dying. I pulled the terminals off the battery because that's what all the older mechanics told me to do haha. I know it's antiquated but I didn't know it could potentially hurt the car.

I didn't wanna point the finger at the battery because it's a week old but it's the cheapest battery advance auto has so I wouldn't be surprised.

I'm gonna try and have them replace the battery since it's under warranty.

So should I forget about my belt not being tensioned paranoia? I know it's reccomended to use a 92-94 sc300 alt. Cause of the round plug.Should I go to Lexus and pick one up or is it one of those things I can pick up at advance/autozone?

Thanks alot fellas, you guys are my only source of info for these things and I really appreciate it.

 

[hvyman]

Can get one at auto parts store.

Better to check the voltage coming out of the alt itself. Should be around 13.5-14v. 12v is not enough.

 

[jaze]

Quick question, is the voltage regulator internal on 1jz's?