timf

I suspect my alternator might be on the way out.

On the drive home I noticed the battery voltage on the dash was less than 12V, so when I got home I double checked with my digital voltmeter and yep it was low.

I turned on the headlights to see what would happen but they struggled to ignite and the battery voltage stayed <12V.

Revving the engine had no effect on battery terminal voltage.

No warning lights on the dashboard.

I replaced the battery a few months back as the OEM gave out.

Questions:
Are there any codes I could pull to determine the alternator charging current or lack thereof ?

How difficult is an alternator DIY ?

Looks like I might be getting my hands dirty again after just replacing the spark plugs and coils :-)

One last observation - I did notice that after a restart for a few seconds the battery voltage went up to just under 14V then settled back down to under 12V. Not sure if this tells me the alternator started to charge then gave out.

Might have the battery tested at where I bought it from just in case it's failed - unlikely.

Thanks again guys, Tim

PS posed this same question 6speed - but figure this is the more technical forum :-)

dr90254

IS your turbo a daily driver?
If not how many days in between drives do you do?
What is the distance in miles that you drive each way?
Do you use a battery maintainer or trickle charger?
What aftermarket electronics do you have installed (K40 radar jammer; XM sat; etc etc)??

Macster

Have the battery tested and while you're at it check *all* connections at the battery and at the other end where the battery cables connect to whatever.

Could be alternator but before you do to the trouble and expense of replacing the alternator you want to be *darn* sure it is the alternator that needs replacing.

Sincerely,

Macster.

timf

HI guys,

thanks for the tips and questions - and yes I want to be 100% its the alternator before delving in there :-)

I thought I'd dodged this bullet about 4 months ago when the battery gave out and replaced it.

To answer your questions - I drive it 4-5 times a week to and from work (20 miles each way)- plenty of time to charge the battery etc. Engine cranks vigorously every time I start it.

No need to use a battery maintainer.

All battery connections are good - visually checked - plus it cranks ok.

I keep a close eye on all gauges and I'm pretty sure this issue has just arisen on the way home tonight.

Stock electrical system - nothing which might drain the battery adversely.

I'm an electronics engineer by trade and it all points to the alternator this time....

Any more ideas ?

Macster

Try another battery -- any reasonable sized battery from another vehicle -- to see if the voltage jumps up then falls down again.

Or take the battery out of the car and have it tested for goodness.

As an EE you ought know about infant mortality.

If you can eliminate the battery, and the connections then about all that is left is the altenator and its circuitry. Check all wiring connections for any signs of corrosion or broken pins or missing pins.

Sincerely,

Macster.

timf

Hi Macster,
Yes premature failure of the battery did cross my mind - but as it cranks the engine so strongly and the fault is so repeatable - eg battery voltage goes up to13.8V after a restart when the alternator is cool then drops back to <12V after about 10 seconds and never rises again despite rpm.

I'm having to conclude it is the alternator - either brushes or electronics or both. Maybe even the connector on the rear ? The engine has only done 20,000 miles.

Wouldn't mind having a shot at repairing it myself if I can get the parts :-)

But I'll do a few more tests as you suggest to confirm one way or the other.

Thanks again for your guidance !

Tim

s996

I had the exact sx at 16k miles, swapped alternator out with a new one in less than 2 hours. Great way to spend saturday morning! . There are also great directions/ pics on the site.

timf

s996,

A bit more googling reveals another possibility - it could be that the alternator clutch pulley has failed. I'll check that when I remove it.

I've found the DIY on 6speed - but will find the one here also. Seems none too difficult.

Thanks Tim

timf

So I've removed the alternator - pulley clutch seems ok, but internal connections to rectifiers are corroded. So I figure to time to replace it with a unit from Pelican rather than having it rebuilt locally.

The bolt holding idler pulley in front of the alternator place was really tight - so I'm wondering if anyone knows what the torque settings should be for re-assembly (all the bolts - alternator, idler pulley etc) and if it's worth replacing the idler pulley while I'm in there ?

Guess the real fun begins when I re-assemble later next week !

Thanks again for the help and guidance.

Tim

dr90254

keep us posted! i like the updates

timf

Update - especially for dr90254 :-)

I discovered a couple of things.

First,the regulator can be changed for about $23 it's part number is Transpo IB225 VR BO. Available on eBay.

(A fellow over on 6speed told me the part number).

This is most likely the root of the problem due to the nature of the failure (sudden abrupt total loss of charging current) fyi all bearings / windings seem good.

Secondly - as I've opted to change the whole alternator (just being ****), while I was on eBay looking for the above I stumbled upon a specialist with excellent feedback located in LA who can offer a brand new OEM alternator for about half the cost of a rebuilt unit from other sources with no core charge.

So I ordered one and will be fitting it later this week - in the meantime a chance to polish a few things in the engine bay :-)

I may order a regulator for my original alternator just for kicks and as a potential spare.

Stay tuned - Tim

Macster

Good news. I wonder where the LA source gets his half price OEM alternators from? I have heard/read -- but have not verified this -- that for instance a Boxster alternator is the same one on a VW Passat though I forget the engine size now. (I think I have this info in my notes, though.) (I bought a replacement for the electrical portion of my Boxster's ignition switch from an Audi dealer parts department. In fact the parts counter clerk told me he sells around one per week to Porsche owners.)

Thus I wonder what other make or model of car the half priced Turbo alternators come from?

I do not like rebuilt alternators, starters, A/C compressors, etc., but do not mind using a new one even if I have to buy it from another car maker's parts department as long as the replacement unit is the right size, capacity, etc., and has the right electrical connectors.

Sincerely,

Macster.

timf

Hi Macster,

I agree with all your comments - check your PM's.

Tim

timf

Hope I haven't jinxed myself - fitted new alternator and now getting a healthy 13.8V even with a heavy load (headlights, heated rear window etc).

s996

nice job!!!