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RPM surge and electrical surge; voltage regulator?

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YellowJacket
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Joined: Sat Apr 29, 2017 2:28 pm

RPM surge and electrical surge; voltage regulator?

Post by YellowJacket » Sat Apr 29, 2017 2:46 pm

2005 Freestyle SEL AWD with 196,000 well cared for miles. Experiencing engine RPM surge at idle and low speeds along with possibly related electrical surges that cause dash lights and headlights to brighten and dim, needle gauges to periodically flat-line, and AC motor to sometime shut off. Alternator was replaced at Ford in 2014 and has checked out as OK three times in March and April. Battery was replaced in 2014, and again this month (under warranty) after three dead battery incidents. Throttle body was replaced in 2011. Induction system was fully cleaned and serviced last August by Ford, and PCM reprogrammed after a more pronounced but separate engine surge problem had me close to taking out pedestrians. Removed and cleaned throttle body last weekend, and replaced PCV valve. Local shop says car is experiencing electric surges that reach 19 volts. They tell me that this alternator does NOT have a voltage regulator, but that the alternator output is controlled by cars computer. Local auto parts store seems to back this up by saying they do not show a voltage regulator for this model. Can anyone confirm I cannot just replace the voltage regulator on the alternator (for a cost savings). I don't want to spend $140 on a remanufactured alternator if it won't resolve, or $150-350 for engine control module that has to be coded to my VIN just to see if it will fix. Spoke with local Ford service advisor, who conferred with his shop forman, who did not recommend bringing such a high mileage car in for testing. Said he would have to charge straight bench time for what could be extensive testing that may not point to the cause. I am not getting any check engine or check charging system dash lights, so seemingly no error codes to point to cause.

YellowJacket
Regular Member
Posts: 10
Joined: Sat Apr 29, 2017 2:28 pm

Re: RPM surge and electrical surge; voltage regulator?

Post by YellowJacket » Mon May 15, 2017 10:55 am

Update: I pulled the alternator and had it bench tested at the local O'Reilly Auto Parts. Three consecutive tests all showed it fine. So I ordered a refurbed powertrain control module (PCM) from Flagship One in New York ($228 vs. $1,200 from Ford). It arrived one week after I placed my order, software updated and programmed to my VIN number, with two uncut keys already programmed to the PCM. I've only had it out for one day of test drive, but the problems (RPM surge and voltage surge) both seem to be resolved. The local auto parts tested the voltage output, and it was back in the normal range.

pmassey31545
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Joined: Sat Feb 18, 2017 7:23 am

Re: RPM surge and electrical surge; voltage regulator?

Post by pmassey31545 » Wed May 24, 2017 6:33 pm

Cool. Glad you got it figured out and thanks for the follow up. This thread will help someone out in the future.
2007 Limited AWD
2009 Ford Flex SEL, 2002 F150 Lariat Supercrew, 2005 Kawasaki 1500 Classic, 1999 Toyota Camry

Pete315
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Joined: Fri Aug 10, 2018 10:33 am

Re: RPM surge and electrical surge; voltage regulator?

Post by Pete315 » Fri Aug 10, 2018 10:39 am

Hi Yellow Jacket, I have a 2006 Ford Five Hundred and I'm having similar problems you had. Did that new PCM cure all your problems? I don't know if my problem is the alt,PCM,dash cluster or a combination of them.

YellowJacket
Regular Member
Posts: 10
Joined: Sat Apr 29, 2017 2:28 pm

Re: RPM surge and electrical surge; voltage regulator?

Post by YellowJacket » Fri Aug 10, 2018 11:16 am

No, a week after installing the PCM I continued to have the problem. Even though I had successfully bench tested the alternator, as a last resort (before scrapping the car) I replaced the alternator. THAT solved the electrical problem I was having. Replacing the PCM (at least in my case) was a trip down the rabbit hole. Car continues to work fine as my daily driver to the present day, with 206,000 miles on it.

Pete315
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Re: RPM surge and electrical surge; voltage regulator?

Post by Pete315 » Sat Aug 11, 2018 7:43 pm

that's weird cause I thought the PCM controls the output of the alternator. I know the alt is charging but a couple of times the voltage went higher then 16 volts and all dash, radio, a/c controls, and that limp mode kicked in. once the voltage dropped to normal range, everything worked again. I went to dealership and spoke to their lead mechanic and he said it sounds like the alternator.

Pete315
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Joined: Fri Aug 10, 2018 10:33 am

Re: RPM surge and electrical surge; voltage regulator?

Post by Pete315 » Mon Aug 13, 2018 10:12 am

Well my voltage again shot up yo 17.8 - 18 so I immediately turned off engine to prevent circuits from being fried. This high voltage puts car into limp mode, kills dash and turns off completely the heating/ac display. Yellow Jacket, where did you get your new alternator from? It will be impossible to find a brand new one, they all will be remanufactured. The local guy who rebuilt last alt has been in business for decades and I think it may be possible he installed maybe a defective replacement part even though it's been about 6 months of trouble free driving with this rebuilt alt. My 500 only has 76,000 miles on it.

YellowJacket
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Posts: 10
Joined: Sat Apr 29, 2017 2:28 pm

Re: RPM surge and electrical surge; voltage regulator?

Post by YellowJacket » Mon Aug 13, 2018 10:24 am

I purchased a remanufactured unit from the Advance Auto Parts near my home. Order online for store pick up and you can usually benefit for a 20-25% discount code. I believe it came with a 3 year warranty. The unit I removed had been installed by my Ford dealer just a few years before, and it was also stamped "remanufactured". (Dealer only offered a 2 year warranty).

Pete315
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Re: RPM surge and electrical surge; voltage regulator?

Post by Pete315 » Wed Aug 15, 2018 11:07 am

Well I installed a rebuilt alt in yesterday. The shop that rebuilt my original said it was still under warranty and gave me another alt that he had in stock that was rebuilt. Today car doing exact same thing,volts going above 17 volts when any gas is applied ( at idle it's ok) which basically shuts doing everything and puts car in limp mode. So I'm going to order a new PCM.If problem continues after that the car is getting junked. I just did brakes and rotors all around 3 weeks ago and changed that top engine mount.

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