I have a 1985 Z28 and the other day the battery was dead. I charged it overnight and it fired right up the next day. We were out of town for a week and when I returned the battery was dead again. Charged the battery and it was at 12.6 volts. Started the car and reved it to 2000 rpm and it was registering 14.8 volts so it appears the alternator is good. Nothing on the battery to indicate its age but looks pretty clean and is a NAPA battery. My only concern is whether or not the battery is bad or there is a drain on it. Any way to tell that? I do know that the center console clock is not working so not sure if that can be causing a drain. The only other thing I found last summer was with respect to the radio. I found a wire in the fuse box connected to the battery slot. Traced that wire to the rear of the radio. It was connected to an orange wire coming out of the radio. There was a brown wire that was not connected. I found that there should have been a plug for these 2 wires but it was not there and no connection in that dash for that plug. Not sure why they did that? So the orange wire was supposed to go to 12 volts, which it does and I believe the brown to lights somehow? The radio works fine and is not on when the ignition is off. I am trying to determine if this could be putting a drain on the battery? I have no issue buying a new battery but want to be sure that is the problem. The car has sat for 3 days now and the battery has lost .5 volts. Any advice is appreciated.

 

How old is the battery? Have you had it load tested? Just because it's clean, is a NAPA battery and reads 12.6 Volts means nothing. A dead battery, or one with one or multiple dead cells will read 12.6 Volts.

 

Sounds like a hack job involving the radio. Is the radio stock?

 

Look over the battery for a date code sticker. The car will have a normal small drain but the battery should last at least a week and still start the car.

 

Take the battery to your local auto parts store and have it load-tested. If it proves good, your next step is to perform a standard parasitic draw test, which will determine what to do next.

 

I charged the battery and fired it up and drove the car. Took it to NAPA since it was a NAPA battery to see if they could determine the date and they could not and only said yes it has 13 volts and is good. The I took it to AutoZone and they fully tested the system. Everything checks out good on the battery and the alternator and starter check out good. My only thought is there is some draw on the battery and if not started in a week then it does not have enough to crank the car? Any other ideas?

 

Check for parasedic draws.

 

#1. Check to make sure you didn't leave any dome lights or trunk light on.

#2. Has anyone done anything in that last month where they would have even TOUCHED any wires on the car?

 

While I'm always skeptical concerning the results of "parts store" testing (a topic for a different thread), it seems that's all you have to go on at this point.


Assuming (yeah; I know) all the above that was checked is actually good, as I stated previously, vvvv THIS is your next step.

 

nothing has changed since I got the car last summer other than putting an OEM cassette radio in as the car as it was just am/fm. As I mentioned in the original post the owner for some reason cut the 2 plug connector out of the car and had the orange wire tied to battery in the fuse box and the brown wire unconnected. I verified with the forum in another post that the orange should be 12 volts all the time. The only other issue is the center console clock, it intermittently works. I am considering pulling apart the console and disconnecting it. Last summer I drove the car almost every day so it is possible there was a draw then but since it was driven so much no issue. Living in the northeast waiting for the roads to be salt free has made the car sit for weeks without driving. I have been trickle charging it during the winter but stopped a few weeks ago and hence the issue started.

 

So I was able to do some testing today. With my tester on the 10A setting it was reading between .01 and ,02. Started taking out the fuses one at a time. When I pulled the ACC fuse it went to 0. Is the center console clock on that circuit? If so I am going to try and disconnect that first. I realize this means taking the whole center console out to do this but its the one thing I am suspicious of since it acts erratically.

 

If the center console clock is like most of the old GM dash clocks from as far back as the 50s (I had a 59 Pontiac with one), it has one of the strangest imaginable mechanisms.

It's just ... yerbasic ... clock. Tick tock tick tock like an old mechanical alarm clock. It has a mainspring, balance wheel, escapement, etc., just like any other mechanical clock. Its unique feature is how it winds up: it has a contact on the mainspring and as such moves as the mainspring winds down, and a corresponding one that's stationary and mounted on a solenoid, such that as the mainspring winds down, eventually the 2 contacts touch; when that happens, the solenoid is energized, flinging the one attached to the mainspring back around several degrees, winding it up and breaking the electrical connection. The process repeats every however often; maybe every 15 - 20 minutes or so. This system fails in either of 2 ways: either the contacts burn up and corrode, such that the mainspring contact comes to rest against the solenoid contact but no electricity flows, therefore no flinging occurs; or, the contacts weld up, such that they stay welded together, current continues to flow, but again, no flinging happens. In this latter failure mode the solenoid draws the rewind fling current constantly, which will drain the batt.

Needless to say, it can work fine 50 or 100 times in a row, tempting you to think that it's just fine and causing no trouble; butt then, it narfs itself. If you're lucky enough to be enjoying failure mode 2, your batt drains to nothing. Then when you put a new good hot batt in it, or charge it fully or whatever, it manages to fling itself free once again, and it works long enough to fool you into thinking there's nothing wrong with it.

In short, that clock is a giant POS. I'd recommend getting rid of it and putting something else there. No amount of "originality" is worth dealing with something as Stone Age as that thing was.

 

Thank you, do you know if the clock is on the ACC circuit?

 

Pretty sure it's on one that's full-time batt. You know, being a clock, and all.

 

Then I need to figure out what's on the ACC circuit that is drawing the current if the clock is not on it. Anyone know what's on that fuse?