Dancing ammeter

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fishy68

fishy68

Tyr Fryr's Inc.
Joined
Jan 11, 2005
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Location
Central, IL (Hooterville)
A year and a half ago I rebuilt the wiring harness on my 68 Cuda and upgraded the charging system to 10 ga. wires and also reconfigured it for using the newer style dual field charging system by adding the extra field wire to the new style regulator. I installed a 60 amp alternator, new regulator and new battery at that time also. Everything worked fine for quite awhile but lately I've noticed after you run the car for awhile and the battery comes up to full charge instead of the charging dropping off nice and smooth it starts cycling like your turning the charging system on and off with a switch rapidly. At first I thought the regulator took a crap so I replaced it with a new one and it still does it. No change whatsoever. I took voltage readings at the battery and alternator output with the engine running and there's allmost no difference (maybe .1-.2 volts max). It constantly showed the pulsating on the voltmeter too and made it hard to get a good reading but it was topping off at approx. 15 volts. You can see it in the headlights going down the road. Allmost looks like I'm flashing from dim to brights constantly. Well maybe not quite that bad but you get the idea. You can also see it in the dash lights. I've checked and double checked every ground and connection I can think of. Does anybody else have any ideas?

Again this only happens after the battery has came up to full charge. When I first start it it doesn't do it for a few minutes.

Thanks, Tracy
 
The hunt is on !
Start by trying a different battery.
Check the ground to block and block to firewall.
Bypass that amp gauge and check/clean the billhead connecters.
 
I checked all the grounds allready. I did a voltage drop test accross them and they tested good. I don't have another battery but may see if I can find one to borrow to test it with. When I rebuilt the wiring harness last year I replaced all the connectors on the harness and bulkhead connector. It would surprise me if that is a problem but it's an easy test so I'll have a look tomorrow. I hate to bypass the ammeter since it's the only thing that shows me if it's actually charging. I heard a while back that somebody makes a voltmeter that goes in the place of the stock ammeter so it eliminates the big power requirement being transfered through the bulkhead but I don't remember who sold them. If anybody knows please post it. I'd appreciate it.

Thanks for the reply Red.
 
I started the hunt with battery as most likely. The amp gauge btpass and IVR removal (not mentioned B4) are deeper in the woods. Good luck
 
If you are seeing it on the amp meter and on a seperate volt meter I would look for a bad rectifier diode in the alternator. Sounds like the diode is intermitant and acts up when it's warmed up.
 
dgc333 said:
If you are seeing it on the amp meter and on a seperate volt meter I would look for a bad rectifier diode in the alternator. Sounds like the diode is intermitant and acts up when it's warmed up.
Click to expand...

As I thought about it this weekend I was thinking maybe it could be a leaky or intermittent diode causing it. Since I haven't been able to find a battery to borrow I'll check out the alternator diode pack pack. It's a rebuilt alt. and seems like they just don't last like they used too.

Thanks, Tracy
 
Just thought I'd let you all know I got the alternator off today and took it apart and it was a broken diode pack. One set was ok but the other set only had 1 of the 3 lugs attached. The other 2 diode connections were just dangling there. I'm surprised it was charging as good as it was.
 
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