Please Help!

[SupraDerk]

Ok, so I posted a couple weeks ago about having my car taken to the shop and being there for like a month and a half and having a ton of new problems. Well I fixed most of them, but then I noticed that the "brake" light and "battery" lights were on.

Well, my dad figured it was the alternator, so I found a new alternator and put it in, then I found out that my battery was dead, so I got a brand new battery today.

Well the first time I started it up with the new alternator an battery, the "battery" light and "Brake" lights were still on. So I took the car to autozone to get the charging system check, turned out the second alternator (I got it from a member on here) was bad too.

So I just sprung and bought a brand new alternator (lifetime warranty :biglaugh: ). So then I changed the alternator again! This time started the car and "battery" light and "brake" lights turned off and I was like ok, now it's all good.

So then I took the car out and drove around for about 2 hours to make sure nothing else went wrong. Well I was on my way in and looked at the voltmeter and noticed that the voltage dropped to 9v. So I was like crap I need to get off the street, and as soon as I pulled into a parking lot, it dropped to 6v and the engine started running like crap.

I would push the gas, there'd be a lag and then it would rev, then drop, then rev, then slowly go up and then above 2k rev it was fine.

Well I let it come back down from the rev to about 1k and then the engine stalled. I had to get my brother to tow me home and now I'm perplexed as to what the hell is wrong.

I know it's the charging system, but I have no idea what!!! Any thoughts??:1zhelp:

<edit IJ try to use paragraphs as most people won't bother reading it and you may not get the help you need>

 

[SupraDerk]

Oh yeah, and while the car was at the shop, the mechanic told me they rewired the car because they couldn't get it started. (Somehow they rewired it to start without the factory alarm evening having to be grounded. That's all that was wrong with it in the first place because one of those bastards pulled my ground out) and now I don't know what they did and I'm thinking this may be part of the problem. Any thoughts on what they might have done?? Sorry this thread is so long, but I want to try and give as many details on what has happened as possible. Thanks in advance!

 

[supramacist]

YOUR POSTS ARE TOO TOO LONG NO ONE WANTS TO READ A CHAPTER. KEEP IT SHORT AND TO THE POINT, i THINK YOU WILL GET MANYMORE RESPONCES.

 

[SupraDerk]

I fixed it.

 

[Jaguar_5]

Maybe they screwed up one of your grounds?

May seem like a stupid question but are the belt and all connections to the alternator nice and tight?

 

[jetjock]

I dunno what your problem is but it can't be hard to find. The charging system is pretty simple and the alternator is easy to test.

While I'm here I need to dispell some charging system misinformation. Someone here stated the charge warning lamp is part of the charging circuit as in cars of old and a failure of the lamp would disable the charging system. Considering the Supra's level of engineering at the time I found that hard to believe so I did some investigating.

If you have a stock alternator you have what's called a Type M IC regulator. It could care less about the charging lamp being in circuit. Nor does the 7.5 amp Charge fuse matter. It's there only to protect the warning circuit when there *isn't* a charging system problem. A look at the schematic makes this obvious.

The bottom line is you could yank that fuse or the charge warning lamp out and nothing would happen. Your charging system would happily continue doing it's job.

 

[SupraDerk]

Yeah after staring at the wiring diagram for about half an hour I figured it was one of a few things. It turned out to be that the engine fuse had been pulled, my guess is when it was at the shop.

 

[jetjock]

Yep, that'd do it alright. Kudos to you for ferreting it out yourself. I also think you need a new shop.

An interesting item: The ecu modifies injector duration based on battery voltage when the charging system fails. It really tries to bring you home

 

[SupraDerk]

Yep, that'd do it alright. Kudos to you for ferreting it out yourself. I also think you need a new shop.

An interesting item: The ecu actually increase injector duration based on battery voltage when the charging system fails. It really tries to bring you home

That's very interesting, good stuff to know, hah. I almost made it home, I was about a mile and a half out. But yeah, that shop will never touch my car again :icon_mad:

 

[Jaguar_5]

^^ I've had that happen to me before, my alternator failed and car stalled at a drive-through, LOL, thought i was gonna need a jump but somehow she finally cranked over, i had to keep the rpm's above 2k so the alternator would pump out just enough juice to get me home

It's the only time my N/A has ever failed on me though!