Voltage issue...

[whtknt2]

Recently I purchased a stock 2004 Silver Marauder with 44,000 miles on it. I've had the vehicle about 2 weeks now and the voltage dips from 14 (seems normal range) to about 10/12 when stopped at a light etc. It's especially bad when any accessories are on like A/C or the defroster. The voltage goes back to 14 when I continue to drive. Sometimes when its down low it spikes back up to normal. Ford has run diagnostic tests and found nothing. The battery and alternator appear fine under their tests. Another independent shop ran tests and they too couldn't find anything. To date they're only suggestion is to install a 200 amp alternator and see if that works. There is no cost to me luckily as the car is under a special 30 day warranty. Anyone have any thoughts as if this might solve the problem or what might be going on? Thanks!

[Spectragod]

Diodes going bad in the alternator, high resistance on your battery cables, loose cables, bad ground(s), Mine had the same problem with 16K on the clock, in my case, it was the alternator. FWIW.

[Zack]

Get a tune with the idle raised, that will help right there.

[Local Boy]

Mine did that too...

Re-charged it...

Then it just went away...


ALOHA

[UncleLar]

Maybe the car has underdrive pulleys on it,Zack's suggestion would cure the problem then.

[Spectragod]

Maybe the car has underdrive pulleys on it,Zack's suggestion would cure the problem then.

Assuming nothing is wrong, and it had UD's, yep, that will fix it. My car had a tune, no UD's and had the same issue, bad alternator.

I would suggest measuring voltages at load, at the battery and at the alternator, see if there are differences, or if the voltage at idle is less than 13.9 VDC.

[musclemerc]

Post a pic of the pullies I bet there underdrive's

[magindat]

Classic UD pulley symptom. Raise the idle. Go on with life.

[whtknt2]

Thanks for the info everyone! I'll look into the alternator again and pulley system along with the idle!

[whtknt2]

Well the shop installed a new 200 amp alternator and the vehicle was still having voltage issues. They checked the pulley's and all seemed stock. When I bought the car it came with a new Optima Red Top battery. They now say after checking some TSB on the car that the battery may not have enough energy in reserve, seems fishy? Instead they took that battery out and replaced it with a traditional lead type much cheaper, sometihng to do with the gel type versus traditional...I've been looking at the few TSB's on this car and can't find any battery related info nor any TSB about alternators that they said they looked at. Scam or no scam, you tell me...thanks

[Bulten Rauder]

Well, it's great you have a nice new 200Amp alternator. The Optima Red Top tells me the previous owner was serious about his battery and they may have had issues?

Take this to a GOOD shop and they should be able to diagnose the problem. It appears you don't want to diagnose/test it yourself?

[whtknt2]

Thanks for your reply. I bought the car through CarMax and only had it for 8 days before the issue. Luckily they have a bumper to bumper 30 day warranty so they did the repairs sort of. They couldn't figure it out so they sent it to Ford and neither could they. So in the end the car ended up at a Fleet specialty shop. I took the car in on March 17 and getting it back April 14. Almost a month...

[UncleLar]

I hope they at least gave you a loaner.

[fastblackmerc]

Well the shop installed a new 200 amp alternator and the vehicle was still having voltage issues. They checked the pulley's and all seemed stock. When I bought the car it came with a new Optima Red Top battery. They now say after checking some TSB on the car that the battery may not have enough energy in reserve, seems fishy? Instead they took that battery out and replaced it with a traditional lead type much cheaper, sometihng to do with the gel type versus traditional...I've been looking at the few TSB's on this car and can't find any battery related info nor any TSB about alternators that they said they looked at. Scam or no scam, you tell me...thanks

Fishy??? you bet. Scam??? +1! Sounds like they don't know what they are talking about.

The battery is only used to start the car, once started it runs off the alternator.

"They checked the pulleys and they all look stock". Know what underdrive pulleys look like... you guessed it STOCK. Difference is in the diameter.

Bet it has UD 's on it and all you have to do is raise the idle..............

[UncleLar]

Okay,so how about somebody who has a set of stock pulleys laying around measure them and let him know what the diameters are. I can't measure mine on the car because it's already been moved and is in storage.