I've got a open 12v to ground somwhere, or a draw on the battery. When the car sits for more then about an hour, the Batt is usually dead, also I have a problem blowing the gauges fuse, although I think this may be in related, the car was swapped from A4 to M6 and I put in a new computer harness, and used the VSS wiring from that, and not the A4-M6 swap, I un-plugged the VSS and I havent blown a fuse since, this leads me to believe that the draw on the batt is from something eles. Also when running the ampmeter does show full charging. The car was down for about 1.5 years then I finally was able to get my turbo kit together, and I'm trying to get it running right again.

So basically any help on tracing the draw would be great.

Thanks
Patrick

 

Ttt

 

Did this problem show up right after you put the new harness in?
If so then check all the connections, check mechanical condition of wires and connectors. Look for a pinched group of wires that may short two together inside the bundle. Also make sure it is the right harness for the right year and so on. The instrument in you pannel in a voltmeter, and since you can charge when running you don't have a hard short to ground, but some kind of slower draw from the battery that takes some time to discharge it.

There is an instrument called a clamp on current meter that will measure current through a wire by clamping it over the wire. You don't have to put it in series with the wire which means breaking the circuit. If you can get one of these you can trace the current to the place it is going to wint the engine off.

Good luck

 

The harness is out of the same year car, except the car was initially a A$ and been converted to a M6. I did a TON of stuff all at once, the car was down for about 2 years, while I have been working on it, so I cant pin point what caused.

Thanks for the help tho
Patrick

 

What are you calllng VSS? The supply line to the PCM? What pins and color wires are you talking about? How old is your battery?

As far as a current draw, you can do the current test without having to purchase any more equipment like the current probe mentioned above. You can put the VOM in series with either the positive or negative cable and remove one fuse at a time until the meter makes a significant jump down close to zero.

You should track down the short that is causing the fuse to blow first before you track down the draw. With the gage fuse out, measure the contacts for 12 volts. One side of the fuse contacts has 12 volts, and the other contact goes to the gages. Now set your meter to ohms and measure the contact that goes to the gages (measure from the contact to ground). If it reads low, unplug the power wire at the gages and see if it goes up significantly. If it does not go up, disconnect the brake switch and check again. Then disconnect the keyless entry receiver, then the DERM. If it still does not go up, the wire is probably pinched somewhere.

Some answers to the first questions will get us further.

 

Use a meter measuring amps or a test light. Connect either one in series between the battery and one of it's cables. Monitor amps or brightness of the light and start pulling fuses until the draw goes away. That will help narrow it down to a certain circuit. There are a few things like the radio, PCM, security, that will draw just a little power, but if your draw is as large as you suggest, the light should be bright or meter showing a lot of amps until the correct fuse is pulled.

 

Thanks, I'll give that a shot. Battery is a brand new Optima. Just traded one that was good for new one, same problem.

The VSS sensor, the one that measures the reluctor wheel on the tailshaft of the tranny. I have two plugs, one from the M6 ecm harness, and one the guy who had the car before me rigged up that isnt connected to the ecm harness. I havent traced the wires to that one, but I never had a problem using that one, and when I put the M6 ecm harness in and using its VSS plug, I started blowing fuses. Granted the car has been down for 2 years, and I've done a ton of stuff to it since it was running last time, so it could be something else, but I know with the plug from the new ecm harness plugged in it blows the gauges fuse after a few feet of driving, and with it unplugged it doesnt blow the fuse.

I'm not driving the car until I get the problem fixed, mainly beacuase I think it has something to do with why the car isnt running right, the car acts like it has a bad opti, I swapped the opti out and same problem. Other things I've done to trace down the weird running problem I've been having include, coil, coil wire, plugs, plug wires, ICM, opti harness, MAF, MAP, and some other stuff I cant think of. The car is running a stock program for a baseline, in open loop, only modification to the program I pulled out some timing up top incase I get into some boost, before I finish up the fuel system. I'm also running a VersaFueler with 84 lb/hr injectors, and I've check that wiring so I know I it is wired up right.

So I'm down to thinking that the car is running strange due to this electrical problem. I'lll do the things you mentioned, and post back, I did rip out an aftermarket alarm that was giving me problems before I finished the car, and it may have something to do that, I'll do some checking and get back to you.

Thanks for the help
Patrick

 

Ah yes brain fart caused me to forget VSS. I believe your harness has voltage going to the VSS when it should not. Check the connector at the VSS with a meter from the purple to the yellow wire to be sure there is no voltage there. Then check from the purple to ground and then the yellow to ground for the presence of voltage. IF there is voltage present, somewhere there is a short to DC or the wiring is hooked up incorrectly.
The yellow wire should go to the PCM on the red connector pin 32. Purple should go to the red connector pin 31.

I've never seen the effects of putting 12 VDC on the VSS lines to the PCM but don't be surprised if the input circuit for the VSS got cooked.

Dave

 

Well I finally got around to checking the draw on the battery. I rigged up a test light with an old 12v light bulb I had laying around, and hooked it up in series from the batt. to the batt. cable, and the sucker lit up bright as the sun, then I checked the voltage from the post to the side terminals on the batt. and it was minimal, then I checked from the + term to the batt. cable, and got ~12.3 volts, that’s one heck of a draw on the battery. I pulled all the fuses from the under hood fuse block and the light went off, so I then started plugging them in one by one and the fans/ACTR fuse lit the light. So it looks like I found the problem of the draw on the batt, I just need to drive the car to see if it may have fixed the miss-fire problem, I'm not holding my breath tho, as I dont know if that much draw on the batt could affect the running of the car? Anyone know?

Thanks for the help guys
Patrick