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Help! Strange charging system symptoms. Bad alt.? #4808768
07/09/18 02:44 AM
07/09/18 02:44 AM
Joined: Feb 2014
Posts: 703
Gold Coast, QL, Australia
19jacobob93 Offline OP
19jacobob93  Offline OP
Joined: Feb 2014
Posts: 703
Gold Coast, QL, Australia
Symptom: washed engine - now alternator intermittently over charging, lights go bright and engine labours every 20secs or so when battery light comes on. Engine power loss under load.

I gave my engine bay a quick rinse down a couple of weeks ago, I've done this dozens of times before without an issue but this time I was heading away and the car wouldn't be started for another 5 days = cold sitting water.

When I came back my battery light was on and the engine sounded slightly labored like the alternator was working over time and I figured it will just be topping the battery up after sitting...
I took it for a drive and the light would go on and off but got less frequent, but now the engine would lose almost all power when under load like setting off from the lights and would take a few seconds to pick back up, which I had to be light on the throttle and fether the revs up. Revved out perfectly fine in neutral/park though.

The battery now showed red or 'replace' so I took it back under warranty but the multimeter test showed it to be fine.
They swapped it anyway and I just fit it but the car still intermittently shows the battery light (every 10-30secs) and when it comes on the engine drops revs a bit like it's laboring and the headlights and dash cluster lights brighten significantly, then back to normal again when the battery light goes off...

Could this random overcharging be a sign of a bad alternator? My guess is water could have sat in it for a few days and caused damage

Car: 2000 Ford Falcon AU2 - 4.0L I6 @330,000km
Oil: Castrol GTX HM 15W50 + LM MoS2
Filter: Ryco Z9
Re: Help! Strange charging system symptoms. Bad alt.? [Re: 19jacobob93] #4808862
07/09/18 07:56 AM
07/09/18 07:56 AM
Joined: Mar 2011
Posts: 1,806
spackard Offline
spackard  Offline
Joined: Mar 2011
Posts: 1,806
It sounds like the regulator to me.

Re: Help! Strange charging system symptoms. Bad alt.? [Re: 19jacobob93] #4809184
07/09/18 12:36 PM
07/09/18 12:36 PM
Joined: Sep 2007
Posts: 966
JMJNet Offline
JMJNet  Offline
Joined: Sep 2007
Posts: 966
In most cases the voltage regulator is part of the alternator.
So, YES, the alternator is bad and needs to be rebuilt.
Depending on the model/type of alternator, a good rebuilder can test it and see if it is just the regulator that needs replacement.

  • 2017 Toyota Sienna
  • 1995 GMC Suburban 6.5L Turbo Diesel

Re: Help! Strange charging system symptoms. Bad alt.? [Re: 19jacobob93] #4809484
07/09/18 06:08 PM
07/09/18 06:08 PM
Joined: Aug 2006
Posts: 9,798
Central Washington
Colt45ws Offline
Colt45ws  Offline
Joined: Aug 2006
Posts: 9,798
Central Washington
You might pull the electrical connector off the regulator and make sure there is no water in there, no corrosion or something messing up the works. Since it was sitting for 5 days, it may have possibly devloped corrosion in the connector if water was forced into it. Might even be worth de-pinning the connector and just checking to make sure.
This is why I dont wash engines ever. Too many electrical items and connectors that can get water trapped in them, more so if you are using a pressure washer, forcing the water into places it shouldnt be.

Last edited by Colt45ws; 07/09/18 06:11 PM.

2002 Ford Crown Vic PI 207k, Ex-Kootenai County, ID Unit #42
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