Battery, Alternator, or other electrical system problem

[usafdarkhorse]

They were load tested like you mentioned above. Isn't that the standard now?

I understand the physics of a battery.

I also understand that, despite how cables and terminals may look, they may have issues, which was the case with my last Z. That is why I said I will try it.

Despite it's simplicity, the car is highly modified and the battery no longer resides in the OEM location. I just hope the problem is as simple as it should be.

Thanks for the suggestions.

[70 Cam Guy]

I'll be watching this thread as well. I just used the same article to swap in a ZX alternator thinking my original one was not charging. My friend had an extra that he gave me that is Bosch reman for a 78-80 Z/ZX.

I am having the same problem down to the voltage across the battery. 12.1 volts with the head lamps on and 12.35 at idle with nothing else on. No change in voltage when holding engine speed at 2500 rpm.

Resistance from alt ground to the firewall ground bolt and battery is 0 ohms, and resistance from the 'battery' terminal to the battery positive and starter positive are all effectively 0 ohms. My fusible link is new from MSA and all of the fuses in the center console read 0 ohms.

I have not tried cleaning the body ground (on the firewall) yet but it's worth a shot. I'd like to think I am fairly crafty with a multimeter but this has given me a big headache. I finally get my carbs sorted so it's running good and I can't get anything from my charging system :stupid:

[usafdarkhorse]

I'll be watching this thread as well. I just used the same article to swap in a ZX alternator thinking my original one was not charging. My friend had an extra that he gave me that is Bosch reman for a 78-80 Z/ZX.

I am having the same problem down to the voltage across the battery. 12.1 volts with the head lamps on and 12.35 at idle with nothing else on. No change in voltage when holding engine speed at 2500 rpm.

Resistance from alt ground to the firewall ground bolt and battery is 0 ohms, and resistance from the 'battery' terminal to the battery positive and starter positive are all effectively 0 ohms. My fusible link is new from MSA and all of the fuses in the center console read 0 ohms.

I have not tried cleaning the body ground (on the firewall) yet but it's worth a shot. I'd like to think I am fairly crafty with a multimeter but this has given me a big headache. I finally get my carbs sorted so it's running good and I can't get anything from my charging system :stupid:

I know right? It's KILLING me!

It's the last thing holding the car back from running fantastically.

[usafdarkhorse]

OK, so today I made sure it wasn't my battery terminals by cutting off the cables just before the terminal ( they were one piece ) and putting fresh cable into new terminals. The negative side looked a little corroded so I had big hopes.

Had the battery charged up to 12.8V and chucked it into the car to try it out.

Started it up. Had really good fuel pressure. Idle bobbed around from 750RPM down to 500RPM. After 10 SECONDS, the car shuts off. I turn the key to start her back up ( standard procedure with the car by now ) and *CLICK*. Nothing.

Check the voltage across the battery. It's 12.25V. Pulled it out of the car and set it on the floor. Between yanking it out of the car, setting it on the floor, and grabbing my multimeter again, the potential had dropped to 12.05V, in about a 10 second span.

An hour later I check it and it reads 11.6V.

Time for a new battery? :stupid:

[70 Cam Guy]

I think I'm going to get my battery tested if that's the case. Though I came back tonight after work to tinker some more and still have voltage. It's not draining that much, still over 12 volts.

I cleaned the firewall ground with scotch brite and sand paper. I snipped the green ends from the battery ground wire (terminal side), exposed fresh wire and re-secured them to the terminal. I can only find the firewall ground and the ground opposite the starter. As far as I can tell, that's it unless I missed something in the service manual or my inspection.

I even went so far as to use my jumper cables from the "BATT" terminal to the battery positive, and the negative to the alternator body. The lamp connection has 12 volts and the diode seems to have voltage on the alternator side. I am starting to wonder if the new alternator is not so good.

I reread this thread and plan on trying an engine>body ground. I won't have time to pull the 'new' alternator for a couple days so we'll see how everything goes with the alt test and battery test.

Edited June 9, 2009 by 70 Cam Guy

[Nigel1943]

This just has to be a ground somewhere. The engine should still carry on running even with low voltage in the battery. Check your alternator wiring again especially the ground. The problem has to be there somewhere.

[70 Cam Guy]

Thanks, I think it has to be something simple like that too. I'll clean the alternator ground connection when I get a chance. The to-do list is clean the alt ground, check the connections again, maybe add a engine>body ground, maybe just replace the battery cables altogether since they're inexpensive. If that doesn't work I'm getting the alternator and battery tested. I really don't want to start throwing parts at a problem, I've never liked going forward without a good diagnosis

Even with all this it's nice to have my carbs sorted and synched nicely now. Just trying to see a bright side

[jwtaylor]

A good reference for battery information is http://www.batteryfaq.org/ The battery state of charge table is very help full, if your battery is reading around 12 volts your at 25 to 0 % charge.

Battery SoC table.xls

[usafdarkhorse]

YES!

So I got a new battery, free since it was less than 2 years since it was bought.

I found the firewall ground, but mysteriously one wire went down to my MS relay box and the other went in an enormous cable that was cut at the end.

Oh well, decided to clean it up anyway.

After fixing the battery terminals and cables, cleaning the firewall ground, and chucking in a new battery, I now get about 14.1V around 2000RPM.

I ran her for about 5 minutes and went and checked the battery potential again. Hadn't changed so I was thrilled.

Took her down the driveway to go down the road and back and my gauge lights go out before I even hit the road!

Looks like I messed with one too many grounds... :mad:

Anyone have the location for the gauge lights ground? :stupid:

Edited June 10, 2009 by usafdarkhorse

[70 Cam Guy]

Thanks guys, all very much appreciated. I'll let you know how it all turns out when I get some more time

I honestly couldn't see anything under the dash that would lead me to believe there are any grounds in there. It's possible there's something behind the kick panels but I wanted to minimize the risk of cracking interior pieces so I didn't touch them. Are there more than the one on the firewall, frame rail opposite starter, and main ground to the starter?

[70 Cam Guy]

After cleaning a couple more connections and getting nowhere, I pulled the 'new' alternator out again and went to Pep Boys with it for a test. It failed every test on their machine. So, what I thought was a basically unused bosch reman, was an alternator with a bum ticker. One of my dad's long time customers and our mtn biking buddy works for an auto-electric shop so he'll be able rebuild the ZX alternator I have. As far as I can tell, this is the last thing keeping me from driving this Z

[70 Cam Guy]

After being stubborn and testing everything I could test on the car, I finally threw up my arms and pulled the alternator back off. Pep Boys tested it on their machine and it failed every single test. So to give some closure to this thread, even an apparently unused, off the shelf, Bosch reman can be no good from the get-go.

I had an auto-electric shop rebuild the original alternator and they hooked me up with a new voltage regulator. Well what do you know! It charges and it's running fantastic. I drove it to work today and I was smiling the whole way. Runs like a top and handles great