I have an underdrive pulley and now it wont charge the battery at an idle, I was thinking about just replacing the stock alternator pulley with a smaller one to increase the speed of the alternator and thus increase the voltage at idle. Has anyone else tried this? Does anyone know where I can get a smaller pulley for the alternator and what's involved in switching out the pulley's to correct my charging issue?

Also, my idle is at 850rpm and really dont want to take it up any higher to correct this issues...

Thanks!

 

What voltage do you have at idle? Later! Frank

 

That depends on how much charge I have when I start idleing, if I have been running for awhile on the highway and the battery is more or less fully charged it will start at around 13 and start dropping down to the 10.5 range over a period of a 30 minutes to an hour. I live in Northern VA where there is a lot of stop and go traffic and when it's hot and I have the A/C on, the motor fan as well as the interior cabin fan on full blast along with the stereo going, it pulls it down fast...

 

It doesn't sound like you are charging at any speed. With an 850 idle speed I would think that would offset the under size drive pulley. Later! Frank

 

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It sounds like a crappy battery. I had this same issue. I bumped my idle had my alternator checked everything. Changed to an optima no more problem.

 

If touching the gas pedal for a few seconds doesnt increase the voltage then its not going to help if you get a pulley to increase the speed by 10 or 20%. Does it increase voltage at 1200 or 1400 rpm? 850rpm is more spinning the alt faster than a stock car would with the stock balancer at 650rpms.

If its a manual, try setting your idle to 1000rpm's which is about 20% to mimic the speed it would spin with a smaller pulley. If that doest fix it, the pulley wont.

If its a red top battery, you need a new one. I just went through that. If its not, then you may have a charging issue with your alt. I swapped to a yellow top and it fixed the problem.

Other things people said fixed your same problem:

Putting in new spark plugs (the noise generated by older TR6's can interupt the signal sent by the PCM to start it charging).

Battery posts dirty

Bad connection at the starter. One guy tried alt swap and different batteries with no relief and he ultimately found melted contacts on the starter which once changed out, the car charged fine.

Some alternator issues can be fixed by spraying contact cleaner into the end cap of the alt and in the back end.

 

Good info, I think the pulley is the fix I need, it'll start charging into the 13.5 plus range at about 1000 rpm unless the battery has dropped real low. I replaced the Red Top 3 times and then finally went to the Blue Top which is much better, I believe the only difference between the Blue Top and Yellow Top is the Blue Top is Marine certified.

The battery terminals have been upgraded in the last month to better accommadate for my Aftermarket Stereo so I know there good and I check the starter often since I burnt a solenoid up previously due to hot headers.

I do run the TR6 spark plugs though, but therey probably dont have more than 5,000 miles on them.

Thanks for all the input!

 

Depend on what Blue Top you bought. If it has a light gray container, it is the same as a Yellow Top, if it has a dark , almost black container, it is the same battery you had, RedTop.

 

.......and he would know

 

Don't discount the spark plugs so fast for a battery charging issue. They will indeed cause noise in the system and cause the ECU/PCM to not tell the alternator to raise the output level. Its happened to me. Going back to the original plugs fixed this same problem for me and others.

 

Please explain how the computer instead of the voltage regulator controls the output voltage. Thanks. Later! Frank

 

The ecu/pcm reads the voltage and frequency via the horn/sense fuse. The computer also monitors the coolant and outside temps as well in relation to the charging system. It looks for the frequency of the alternator as the engine starts up, then tells the alternator to start charging once its up too speed. If there is noise on that fuse which will indeed come from the spark plugs, it may not issue the proper charging commands back to the alternator. Remember too, these aren't the alternators from the days of old, rather they are computer controlled. Now as to the monitored temperature, the computer will up the charge rate in severely cold temperatures to insure the battery doesn't get too cold.
In my case, I changed the plugs out on a whim and suddenly started having charge system fault messages on the DIC. I changed the battery, then bought a new alternator and still had the messages. What I saw when starting up hot, the analog voltage would hang low and not suddenly jump up, indicating charging taking place. Put my foot on the gas and then it would jump up. But, at times, idle, fans all running in the summer heat, it would fall back down and I would get the fault message again. Another forum member, SgtRod told me about the spark plugs and I'm thinking, no way, not possible could the plugs have anything to do with the charging system. Taking his word for it, I switched back to original plugs and sure enough, the problem went away. It was only then that I opened the maintenance manuals and read up on the charging system.

 

Sounds similar but not exactly the same as my Duramax. In cold weather the alternator will not go to charge mode for 30 seconds. This allows all the heaters to time out. Don't want to overload the alternator. Your description sounds overly complicated. Later! Frank

 

loose cylinders (broken spark on install or ripped wire) and the PCM nknows this. cant exspect it to continue to bump up the alternator voltage when you have lost HP. safety kind thing. As with any job that after something isnt like it was before you have to ask yourself" whats up"

 

Great explanation of the plug issues in regards to charging, I think I'll go back to the Stock plugs and see what happens, I might even change the wires while I'm at it...

Thanks!

 

I can only say that forum member SgtRod found this issue, so he gets the credit for the find. I didn't believe it either but on his word, I put the original plugs back in and sure enough, my charging problems went away! It may not be the issue here, but it should not be discounted either.

 

For the cost of new plugs, it's worth a try, I PM'd SDPC to purchase the pulley, plugs, wires, and insulators...

I also have an issue with stereo noise from the my 2,1600 watt Orion amps, even with huge solid grounds right to the battery. Maybe it'll help with here as well.

I've also been told that with some of the aftermarket stereos, the plug wires and plugs themselves can interfere with Radio reception. Anybody with insight on this, please chime in, especially if I should use a different type of Plug wire.

Thanks!