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Author Topic: Battery light on, 17+ volts at idle, voltage regulator?  (Read 809 times)

RisingTide194

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    • 1994 Mercury Capri Base, 2002 Subaru WRX
Battery light on, 17+ volts at idle, voltage regulator?
« on: April 18, 2021, 04:57:39 PM »

Hello all!
I am new here, my wife has had a 1994 N/A 5SP sitting at my in laws for about 10 years that I'm in the process of slowly fixing up to get back on the road. I've been perusing the forum and already got a lot of great info (most recently to get a gas tank for a Mazda 323!). I am a certified tech (currently a service advisor) so I know my way around a car, but I am not as familiar with older systems and wanted to make sure I'm not missing something.

I recently got the car running again this spring after a battery charge and the tank replacement, and the battery light is on at all times when running/driving. The battery is resting at 12.5, but battery voltage at idle jumps to a out 14.5 then just climbs and climbs as high as 17.4v within a couple minutes of idling (shut it off at this point). When I added some loads (headlights, blower fan, etc) a separate time it seemed to stay under 16v but battery light remained on. From what I've read there is a voltage regulator that is separate from the alternator itself. At this point I'm thinking I need to replace that regulator since it seems to have gone bad. I wanted to check and see if anyone's had a similar problem or has any advice about these cars that I'm missing before I do that since it's a $170 part and I haven't yet found a used one. Thanks for any help in advance, and you'll probably see me around here occasionally!
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Rocketman

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Re: Battery light on, 17+ volts at idle, voltage regulator?
« Reply #1 on: April 18, 2021, 05:38:51 PM »

There's two different alternators for the Capri, make sure you get the correct one. The voltage regulators are internal to both units so you will need to replace the whole alternator.
It does sound like a bad regulator.

A word of warning, the aftermarket & rebuilt alternators come with a pulley that isn't quite correct and will tend to eat belts.
Keep the original pulley from your alternator and install that on your replacement alternator to keep your capri's belt appetite down.

And welcome to TeamCapri!
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1.8L Turbo All Wheel Drive Capri... the "GTXR2"


greywolf27030

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Jack Byrd

RisingTide194

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    • 1994 Mercury Capri Base, 2002 Subaru WRX
Re: Battery light on, 17+ volts at idle, voltage regulator?
« Reply #3 on: April 22, 2021, 09:33:03 AM »

There's two different alternators for the Capri, make sure you get the correct one. The voltage regulators are internal to both units so you will need to replace the whole alternator.
It does sound like a bad regulator.

A word of warning, the aftermarket & rebuilt alternators come with a pulley that isn't quite correct and will tend to eat belts.
Keep the original pulley from your alternator and install that on your replacement alternator to keep your capri's belt appetite down.

And welcome to TeamCapri!

I did see some posts about the pulley - I'll definitely swap that. Thanks for the info! I'm going to get one ordered and that'll be the next fix along with the exhaust (still trying to figure out if I want to register it as Classic or Antique and thus if I really NEED a catalytic converter or not...we shall see)
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RisingTide194

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    • 1994 Mercury Capri Base, 2002 Subaru WRX
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RisingTide194

  • Newbie
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  • Posts: 5
    • 1994 Mercury Capri Base, 2002 Subaru WRX
Re: Battery light on, 17+ volts at idle, voltage regulator?
« Reply #5 on: April 22, 2021, 11:26:07 AM »

There's two different alternators for the Capri, make sure you get the correct one. The voltage regulators are internal to both units so you will need to replace the whole alternator.
It does sound like a bad regulator.

A word of warning, the aftermarket & rebuilt alternators come with a pulley that isn't quite correct and will tend to eat belts.
Keep the original pulley from your alternator and install that on your replacement alternator to keep your capri's belt appetite down.

And welcome to TeamCapri!

I'm not sure if I'm just missing it - but what's the difference between the two alternators? Can I just order one of the remans from Rock Auto or is there more to it?

Thanks in advance.
« Last Edit: April 22, 2021, 11:30:33 AM by RisingTide194 »
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Rocketman

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Re: Battery light on, 17+ volts at idle, voltage regulator?
« Reply #6 on: April 22, 2021, 09:19:21 PM »

The early model Capri came with an alternator with an external fan made by bosch, it is 85A I believe.
The later models came with a 70A Mitsubishi unit, internal fan.

The plugs on the back are different, as is the lower mounting bolt.
They are physically interchangeable but you will need the correct bolt/plug for the unit you are using.
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1.8L Turbo All Wheel Drive Capri... the "GTXR2"


RisingTide194

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    • 1994 Mercury Capri Base, 2002 Subaru WRX
Re: Battery light on, 17+ volts at idle, voltage regulator?
« Reply #7 on: April 23, 2021, 11:09:04 AM »

Okay great, I saw you said in another thread about the fan but I wasn't sure if that was a way to identify the two different ones or not. Didn't know about the plug. I think mine has no fan but I will double check and then get it ordered. Thanks again!
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