Holy Crud!!! More Under the hood electrical issues... PLZ HELP!! PICS!!

[snb778 5,000+ posts]

Ok, so my battery light went on the other day.. I tested it.. it read 12.5 I have an upgraded HO alt. 180Amps in there. Have the big 3 done, BUT I think something was wired wrong.

I went to go get an ALT test today at Merlin... He said while the car was on, it tested at 11.90. He tested it at the battery with some kind of computer though so I dunno how reliable it is...

He said to take the car home, start the car, then take all the - terminals off the battery... I did that, car died... BUT...WHen I start the car, and leave the batt- to chassis on, car stays on.. THEN..... i take the power wire off the + terminal....car dies???????????!!!!!

Also... car tests at 11.9 with car on... and slowly drops WITH Batt- connected... I take it off...voltage goes up, and continues to slowly charge the batt...

Here are some pics...

Car on, all - terminals taken off



Car on with - terminals connected... notice the voltage dropped



THIS ONE... I had the car started.. took all the batt- off...THEN took the POS power wire off...car dies??????????



This one.. notice again... I put the batt- back on and the voltage drops again...



Alt+> bat+

Alt-> batt-

Batt-> chassis GND

Batt-> Starter

Batt->***** GND ( i know its supposed to be engine, but that's what the shop did...can't see that bein the problem though)

I also have 2 batcap800 equivalents in the back, but im almost positive they are hooked up correctly... had another thread on doin that right...I did what everyone said... seemed to work fine

Click to read more...

 

[iamamp3pimp 5,000+ posts]

let me get this right

voltage goes up when alt is disconnected?

car dies when batt is disconnected?

bad alternator

 

[iamamp3pimp 5,000+ posts]

alt is draining batts thats why voltage goes up when you disco it. they are sitting at a higher voltage without the alt on

batts are running the car, thats why it dies when you disco them.

 

[Rashaddd 5,000+ posts]

alt is draining batts thats why voltage goes up when you disco it. they are sitting at a higher voltage without the alt onbatts are running the car, thats why it dies when you disco them.

x2

 

[Doingstuffwell 10+ year member]

never remove battery from the loop when engine is running.. its a great way to blow out electronics or the alternator.

sounds like a dead cell in the batt, or the alternator has gone bad.

 

[twisztdauthorit 10+ year member]

sounds like a bad alternator... your car should run when u disconnect the battery

 

[snb778 5,000+ posts]

sounds like a bad alternator... your car should run when u disconnect the battery

it does... IF I keep the power wire connected... as I said.. I can start the car...take the -terminal off..car stays on... I disconnect the Power wire to my amp... car dies

 

[snb778 5,000+ posts]

think im gonna try to get a video for you guys... I dont want to pay MORE money to get the wiring checked...end up having the wiring be fine, THEN pay MORE money to get the ALT taken out

 

[snb778 5,000+ posts]

UPDATE

just went out to see how far it has charged in the last 30-40min. Its up to 12.30from 12.10. This is with all the - terminals disconnected...just sucks cause I know once I start my car up to use it next time its goin right back to 11.8ish

 

[Moe Lester 10+ year member]

Is all of this at idle? rev the engine up and see what your voltage does

 

[snb778 5,000+ posts]

it really doesnt move.. maybe .1-.2

ANOTHER UPDATE... just went out there again.. Hooked up the Chassis GND to the batt CAR OFF... Voltage starts to drop????????????????????????????????????

So ANY wire I hook up to batt-... voltage starts to drop... car on AND off.... but the Main batt- immediately drops it to 11.9ish... other batt- wires just slowwwwwwwly discharge it.

 

[jrwalte 10+ year member]

sounds like a bad alternator... your car should run when u disconnect the battery

That's not necessarily true. The alternator produces power by means of an electro magnetic field which is controlled by the regulator. Most cars run the positive to the fuse box from the bat, not the alt. So if you disconnect the positive from the bat that goes to the fuse box, your car is going to stall. Computer gets no power and your alternator regulator gets no power for the electro field. It works with the bat neg disconnected because the alt is grounded through the engine block to the chassis and all the wires in the fuse box have a ground to chassis.

Have you had a local shop load test your battery? Sounds like either your alt or bat are going bad. One reason I can see the voltage in the system dropping more when bat is connected is because the alt is going bad and the battery is drained. It's causing a big strain on the weakened alt when connected because it is trying to charge.

Start the car again and take a voltage measurement at the alternator, not the battery, with the bat neg disconnected. Take another reading from the alt with the engine rev'ing at least 1500RPM as well.

 

[snb778 5,000+ posts]

That's not necessarily true. The alternator produces power by means of an electro magnetic field which is controlled by the regulator. Most cars run the positive to the fuse box from the bat, not the alt. So if you disconnect the positive from the bat that goes to the fuse box, your car is going to stall. Computer gets no power and your alternator regulator gets no power for the electro field. It works with the bat neg disconnected because the alt is grounded through the engine block to the chassis and all the wires in the fuse box have a ground to chassis.
Have you had a local shop load test your battery? Sounds like either your alt or bat are going bad.

yes, we have established this.

And no, im not talkin about the power wire from the fuse box.. im talkin about my big asz power wire goin to my amp.

NOW... is there ANY WAY that the batcaps in the trunk could be causing this problem....I don't think so...but I guess its possible

 

[casper97ta 10+ year member]

Like others said, Sounds like the alt. is bad. Depending on how long its been going out, your battery could also now be shot.

 

[jrwalte 10+ year member]

The bat caps in the trunk could be what's going bad.

And I didn't realize you only disconnected the power wire to the trunk which caused your car to stall. This probably means the bat caps in the rear were providing the power to your car's electrical and kept it running. Once you disconnected the power to the rear, you broke that connection.

I edited my first post after you replied. Give us voltage measurements from your alt at idle and at 1500RPM +. Give us 3 measurements:

1) the front bat neg disconnected

2) the front connected and rear pos disconnected

3) everything connected