Battery or Alternator/voltage regulator?

289fia_cobra · #1 (**permalink**) 09-12-2013, 09:23 PM

I took my FFR to work and to my nephews 'car show' at EA today.
On the way home from work, I noticed my volt meter was under 12V. Normally on any given time, it's between 12 and 14 so call it 13V.

No matter how high I revved, it remained below 12V. I made it home but now to figure out if it's the alternator/regulator or battery.

The alternator is a 100A Power Master single wire so the voltage reg. is built inside.

The batter is a red Otima I've had since early 2006 so it's over 7 years old now.

What's a good way to check the alternator and should I just replace the Optima due to it's age or keep it longer???

TIA

Texasdoc · #2 (**permalink**) 09-12-2013, 09:52 PM

Check the voltage of the power wire to the altenator with the car engine running. It should be arount 14.5. If it is at 12V, your alternator is not charging.

Paul F · #3 (**permalink**) 09-12-2013, 09:58 PM

Harbor Freight has voltmeters for about $7 if you don't have one.

Many parts stores will test the alternator for free if you take it out of the car and bring it in.

289fia_cobra · #4 (**permalink**) 09-12-2013, 10:21 PM

I have a VOM. Time to test it this weekend. Nice thing about these parts, not very expensive compared to a Bosch unit at over $200!

PANAVIA · #5 (**permalink**) 09-13-2013, 12:45 AM

My rule of thumb ; - at idle the alt should be at 13.6 or better , with full 14.5 at 1500/2000 rpm - as for amperage if you are stuck in traffic , and your alt is rated at 100A , that 100A is available at 2500 or so RPM and up.

A 7 year old optima is probably running on borrowed time, but if it holds a charge , keep on using it.

If you need further help , we would be happy to see you.

Steve

m5extc · #6 (**permalink**) 09-13-2013, 01:09 AM

Herman, it sounds like your alternator or internal regulator has gone. You want to take voltage readings at the battery and at the B+ or power post of the alternator. You may also want to run an amp test or an inductive lead on the power out wire of the alternator. I have not had to rebuild a Powermaster before but many internally regulated alternators have replaceable brushes and regulators. Let me know what you find and if you need any help.

Andrei

PANAVIA · #7 (**permalink**) 09-13-2013, 02:45 AM

If your powermaster is based on a GM 12si , then they sell a rebuild kit via summit.- I need to get an inductive amp dealie....

289fia_cobra · #8 (**permalink**) 09-13-2013, 07:32 AM

Thanks Steve, Andre.

Yeah, I seem to recall a rebuild kit at Summit. I'll put a trickle charge on the battery tonight and Sat., see if it holds voltage (yes, take a before and after reading then let it stew like half a day off the charger and take a final read.)

Wondering if antifreeze being sprayed on it for a few years, had anything to do with the alternator going out so soon - I had a nasty run of radiators leaks with a Ron Davis unit for a many years before getting a regular AFCO radiator. Fluid would be all over the housing of the alternator and I think later on, I could hear a faint squealing from the alternator but a few months later it just went away - I was fearing maybe all that coolant washed aways some of the bearing lubricant in the alternator.

I may just put in an order for a new Optima. I've NEVER had a battery last this long in any of my cars (I have 5). The Audi is still to be figured out - it was build and running in 4/2008 so it's had the original battery in the trunk for just over 5 years now.... tick tock...

jhv48 · #9 (**permalink**) 09-13-2013, 07:58 AM

When mine did that the first time, I found the wire to the alternator had broken at the alternator post. The second time this happened, it was the internal voltage regulator. Finally had to replace the alternator.
Do as others have suggested. With the engine running, check the voltage at the battery. If no charging is showing, put the tester on the one wire post at the alternator. If no charge, you've found the culprit. Either rebuild or replace it.

CHANMADD · #10 (**permalink**) 09-13-2013, 01:28 PM

With an Alternator .....start the car and whilst it is running......... disconnect the negative battery terminal............If the alternator is OK it will continue to run, ..if its bad it will die directly...........

CHANMADD · #11 (**permalink**) 09-13-2013, 02:19 PM

and yank it of quickly so you're not making sparks.......

cobrarkc · #12 (**permalink**) 09-13-2013, 05:33 PM

Actually the best and safest way is with the volt meter. it shouldn't matter if you check it at the battery or the alternator unless your battery cable is corroded. If you check the voltage at the battery before starting the car and then after it should go up while the car is running, at least 13.5. If I just went through and couple Transpo voltage regulators with a 100 amp alternator, seems that is to many amps for them. Installed a 110 amp si GM alternator and I get 14v at indle with everything on including the electric fan.

289fia_cobra · #13 (**permalink**) 09-13-2013, 08:03 PM

THanks everyone but the problem is a bit easier than I thought... the main cable from the battery to the alternator appeared to finally burn off; it was just hanging.

*EDIT*
Ok, I finally got a flashlight in there; the rubber snub is still there but on the burnt end of the cable I noticed a green corrosion; this is possibly due to the radiator leaks I had for a few years before getting rid of the Ron Davis radiator and replaced it with a Afco unit. So now, I'm trying to determine the root cause of this issue. I don't think corrosion alone would have weakened the copper ring connector but perhaps coupled with engine vibration, perhaps it was enough.

Got guest over right now so I couldn't take off the alternator but will tackle this tomorrow morning. I should have a clear idea (I'll provide pictures.)

Jaydee · #14 (**permalink**) 09-13-2013, 08:19 PM

Do not disconnect the battery whilst it is running. The alternator needs a voltage signal, if it doesn't it can run away and produce over 18volts and blow any electronics. This can happen if you jump start a car with a open circuit battery. If you suss an alternator, just strike it with a hammer whilst the engine is running, this sometimes kicks it into life, when the brushes are worn or there is a loose connection. it will get you home, maybe.
JD

PANAVIA · #15 (**permalink**) 09-19-2013, 12:08 AM

Vibration might be part of the issue - - if it was strong enough to crack a radiator...

289fia_cobra · #16 (**permalink**) 09-19-2013, 09:20 PM

Good news, the kit came in yesterday, finished installing it late last night. I made sure I gave the alternator plenty of "service" slack to minimize the amount of movement; I have the ring connector facing straight to the floor w/ a 6" radius before it makes it's way to the frame. Prior to that the ring connector was at a 3 or 9 o'clock position and barely and 'some' slack to what I felt should have been ok (guess not). And I'm up to 6ga. wire instead of 8 ga. While 8 ga. should have been enough, the 6ga. wire IMO is stronger because the individual strands are much thicker; something more akin to that of battery wire - the original wire that came with my I-Squared kit looks more like something I'd use for stereo equipment. It's not a stretch to think the thin strands would fatigue much quicker Here's a picture of both cables.

When I got home, the car started right up! Seeing a good 14.3v.

Will probably drive it to work tomorrow to charge up the battery some.