MR2 - alternator issue?
MR2 - alternator issue?
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Twincam16

Original Poster:

27,647 posts

280 months

Wednesday 7th November 2012
quotequote all
Hi all,

Just after some technical advice - I have a Mk2 MR2 (1992 Rev2 no less - all the possible '2's) that is otherwise flawless.

However, recently it seems to have problems starting. The starter motor seems sluggish (increasingly so if it's not been used for a while), it's needing a prod of throttle in order to catch, and all the dashboard warning lights are remaining on until I'm halfway down the road. The battery only registers half a charge (if that) until the engine's off the fast-idle cycle, and using any electrics during the fast idle (windows, radio, heater etc) causes the charge to suffer further.

Thing is, five minutes up the road, it'll be fine and registering a full charge. Also, none of the electrical systems seem to be struggling with the engine off (interior lights, key light, door-open warning light and central locking all work with the engine off after a week in the garage so there's no drain), and the battery seems healthy when I check it with a multimeter.

There was a drain on the battery a while back that was traced to the radio amp. This was bypassed to the ignition circuit with a relay so it couldn't come on when the engine was off.

Also, the car has no problems hot-starting. This is purely a cold-start issue, which leads me to think it's the alternator not holding its charge.

Before I look into replacing the alternator, is there anything else I should check?

_Al_

5,618 posts

280 months

Wednesday 7th November 2012
quotequote all
The alternator doesn't hold any charge.

How old is the battery? Personally I'd be inclined to jump it from another battery when cold. If it starts fine, chances are your battery is shot.

Note: batteries can easily show 12V to a multimeter, but when you're trying to pull serious current while starting they can struggle.

geeks

10,985 posts

161 months

Wednesday 7th November 2012
quotequote all
Sounds like a dead battery!

Run a multimeter over the terminals when the engine is running you should see about 14v from memory. The fact that it seems ok when warm and dud when cold also suggests battery, also that it seems ok after a while points to a battery top up...

Twincam16

Original Poster:

27,647 posts

280 months

Wednesday 7th November 2012
quotequote all
I'll give that a go. I suppose the battery could have suffered back when it was suffering the drain from the dodgy amp. Thing is, in between that relay fix and the start of these problems it started regularly most days for a clear month with no issues at all.

Meoricin

2,880 posts

191 months

Wednesday 7th November 2012
quotequote all
It wouldn't be unusual for the alternator to start giving up around this time of year, since water drains through the engine lid directly onto it.

dabofoppo

686 posts

193 months

Friday 9th November 2012
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Check your alternator plug mine somehow fell out the day after i got my 2 and now occasionally it comes loose and causes similar problems. Its quite easy to reach down and push it back in.

clarkson22

471 posts

186 months

Monday 12th November 2012
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mate check battery with multi meter on idle, should be 14.2 or around there if not alternater is goosed,