Matt Sheppard

I am a lttle dense and I dont always seee the forest through the trees. I dont understand something with my red car. There are two components to our chraging system, well, three if you count the voltage reg., right.

My battery is a 3 month Optima Red top and I've tried 3 different alternators and they all charge at 13.7, but the battery quickly drops down to 12.1 Volts after shut down (pulling fron aux. waterpump) and to 12.5 Volts when sitting for a while. It barely cranks when I go to start it. All these are measured w/ a multimeter. When I drive, the stock Volt gauge reads just over 12 V. Shouldnt it be charging over 14 V. when running?

I have cleaned all my contacts, run a supplimentary ground at the front of the motor (frame to one of the upper balance shaft bolts). What can I be missing? I have been chasing this for 6 months now and I need some help. Can the old stock cables be responsible for all the resistance?

bearone

i just ordered dan's/iceshark adjustable vr for the same problem.

i've been charging the batt every couple of weeks.

87951

RKD in OKC

After searching the archive, I would say check the connections to the starter. Seems they are in the charging circuit somehow and effect the alternator prime causing a low output. There are also some interesting bits on the internet about the alternator trouble bulb itself effecting the prime also. And that if it is ever replaced to be sure to replace it with the correct bulb.

Charlotte944

Very good points. The starter connections are a "tie point" for the positive side of the electrical system. Any loosness or corrosion here and the ability of the alternator to keep the battery charged is severly affected.

The battery warning light is actually a part of the charging circuit. If this bulb burns out, the alternator will not charge the battery.

Beyond that, you need to make sure that EVERY connection is clean and tight. Clean the outside of the battery and the batery box with baking soda (Arm and Hammer) and water. This will neutralize any salts/acids and prevent corrosion and "parasitic grounds". Also make sure the alternator belt is tensioned properly.

For the voltage drop after shut down, you need to put your meter in series with the battery and measure current flow. Pull fuses/relays until the current flow stops, then put fuses/relays in one at a time until the current flow starts. This should tell you where the drain is. Things like alarms, clocks, and stereo head units are high on the list of culprits.

If you are still getting a current drain, have the alternator diodes tested. A shorted diode will drain the battery.

GaryK

I have the same symptoms in my car, with a rebuilt alternator, new voltage regulator, and new Optima battery like yours. I've also checked all connections, and believe that, at least in my case, the problem is due to the alternator getting hot since I had to remove the cooling shroud when I installed the large turbo. Would be great if new battery cables solved the problem, though.
Gary
'89 951

Matt Sheppard

Cliff : Thanks for the explanation. I will do the starter conections tonight as well as the baking soda bath. What should the battery posts read on a meter durring normal running?

Gary: It's good to know I'm not the only one. . .

Anyone know a FAQ's I can access regarding testing diodes?

bearone

13.8+ when started.

87951

jns

On another car I had, it had the same symptoms as yours but turned out to be a starter solenoid going out. It gave the impression of a weak battery when it tried to start. Good luck with yours!

RKD in OKC

There are serveral cars here in OKC with upgraded turbos that fitment required removal of the alternator cooling shroud and they have zero charging issues.

RKD in OKC

Measure the battery voltage with the car off and the key out.

Start the car and check the battery voltage, if alternator is working should be higher than with car off. If not alternator is not working at all.

Turn on all the accessories, a/c w/fan on high, headlights w/brights, stereo, etc. then check voltage again. This should also be higher than with car off. If not there is a poor connection to the alternator. Be sure to also check and clean the ground connections.

Note: rust will pass some current, but not enough to charge the battery.

Matt Sheppard

Well, If I'm getting 13.7 @ the battery when running, the circuit is working correctly. If logic serves me right, that means I either have a drain or a bad Optima.

GaryK

Well, mine is behaving differently than yours, Matt. With the car off, the battery reads 12V. With the engine running, it reads 13.7V, as does the dash gauge. When I turn the lights and AC/fan on, it drops to 13V. When I drive the car, particularly in the summer heat, the gauge drops to 12V after a short period of time, and actually just below 12V with the AC and lights on. This doesn't appear normal to me, at least not compared to my other vehicles, nor does it seem to indicate poor ground connections.

And btw, I did have to replace a bad Optima (shorted cell), but it was 11 years old!

Black Arrow

Sorry to bring up a old thread, but its better than starting a new one!

Mine suddenly overcharged big time! At idle 16v, if I turn everything on it goes down to 12v. Its possible to drive the car, but not over 1500rpm! Then I`ll overcharge and toast the battery.

So, could this be the regulator? And is there any way I can test the alternator when its out of the car? I`ve heard somewhere that I need to supply 12v to the alternator, for it to function properly? Or can I just connect the alternator to a drill, and check the voltage output?

Thomas

MitchB

High charging rates are almost always the voltage regulator. They are relatively cheap, so I'd start there.

Black Arrow

Yeah, I`ll trie to change the regulator..

Nobody knows how we can test the alternator outside the car?