Alternator pulley types

[Gold 'N' Brown]

Was just looking at replacement alternators and I see you can get fixed pulley or freewheel pulley with a clutch. What's the purpose of the latter, why is a one used and is there a particular engine configuration that they would be used on?

Just asking out of general curiousity. I will of course check exactly what i have fitted before ordering a replacement.

[Tim Williams]

Early ME7 engines had fixed pulleys and later ones freewheeling pulleys. The freewheeling pulleys are designed allow the alternator to carry on spinning at a higher speed when the engine revs drop quickly. Fitting the wrong type can throw faults codes.

[Harvey]

Here's a video which gives a good bit of info.


https://youtu.be/rXehCcNzq_A

[Gold 'N' Brown]

Checked my pulley today with the serp belt removed. With a screwdriver through the vents to lock it, the pulley does not slip in either direction. So either the clutch mechanism is seized, or it's just not a free-wheel type alternator. What's the chances of a MY2000 Ph2 V70 T5 having the earlier style alt with a fixed pulley?

If for some reason mine came with the fixed style from the factory, I don't suppose it would be an issue to replace it with the free-wheel style, would it?

Also not 100% certain yet if it needs replaced.
- I'm getting some rough bearing hum, which I thought was either the alt or the serp tensioner, but have ruled them out today (perhaps the cambelt tensioner, so will be having the belts done ASAP). That said, when I did the stephoscope test (screwdriver to the ear) on the alternator body it did sound quite noisy with a high pitched whine coming from inside. Problem is I've never done that test on a healthy alt so have no frame of reference :dunce:

- Voltage measured at the +12v terminal on the passenger side of the engine bay was 13.8 with engine running, slight fluctuations downwards by no more than half a volt but never really went above 13.8 either. With engine off battery settled settled just over 12v (12.1 or 12.2 IIRC). So all borderline passable I guess.

- Car always starts OK. I think on the very odd occasion it may have been slightly slower on the starter, but barely perceptible.

- In recent months I've started getting "Low battery voltage" warnings if I leave ignition on and engine off for more than a few minutes.

- Headlights and dash lights brighten if I blip throttle, then dim slightly again when it drops back to idle speed (which is a pretty stable 650rpm). Is considered normal, as it was always pretty normal in some of the older cars I used to own?

[MoleT-5R]

how old is the battery and is it in good condition ?? as it sounds like the alternator is healthy from your tests, so could it be bad electrical connections or a poor/failing battery not storing the charge and giving the Low battery warning you mentioned. A local tyre and battery place could easily test the battery for you ,if you can't test it yourself.

[Gold 'N' Brown]

Not sure on the age of the battery TBH, but I don't suspect it (yet) to be an issue. I can often go days/a week between using the car, and my trips are often very short, so I think it's managing to hold charge OK. I have one of those CTEK trickle chargers that also recondition old batteries (and it works too) and I've used that in the past. Will get it on that again at some point.

[MoleT-5R]

Not sure on the age of the battery TBH, but I don't suspect it (yet) to be an issue. I can often go days/a week between using the car, and my trips are often very short, so I think it's managing to hold charge OK. I have one of those CTEK trickle chargers that also recondition old batteries (and it works too) and I've used that in the past. Will get it on that again at some point.

It was just a thought as you mentioned that the low battery warning would come on if the ignition was turned on and left for a short while when the various electrical systems would be zapping power a lot quicker, than the few low power systems the battery powers when the car is not in use. I do want to get myself a couple of good trickle chargers to keep the MG's batteries in tip top condition as they spend long periods in storage with only few runs out in a year.

[Gold 'N' Brown]

Yep, it's a fair observation, I knew someone would suggest it. It is a possibility but I also suspect the alternator is just not quite charging enough, hence the battery is only just over 12v at rest, it's just not getting a decent charge.

I can thoroughly recommend the CTEK charges that also restore dead batteries. They were recommended to me buy a few people on another forum a few years ago. I figured I could spend £50-70 on a new battery at the time or try one of these. I've revived 2 old batteries that had been run flat numerous times and weren't holding charge any more . Obviously there's always a limit to what you can bring back from the dead and the 2 I've revived might not be as good as new, but they have been given a new lease of life. Had to use one that had been sat in the garage for months (must have been over a year) to jump start the V70 when my little boy left the lights on and ran it flat.

[MoleT-5R]

I like the sound of those trickle chargers, probably could have saved 1 or 2 of the batteries I weighed in on my last clear out... :doh:

Another thought if your alternator is not performing that well is that you could easily change the brush/regulator pack, which are quite cheap and easy to replace. I did this on the Gul when it's alternator failed and it is still going strong after at least a year of daily use, was a pig to get off as the bolts had seized, but once that hurdle was pasted the rest was a doddle.

[Gold 'N' Brown]

Alternator shat itself yesterday. Oh well, I had that coming. Still not got round to doing the PCV yet so will probably do both jobs in a oner.

[jdavis]

The P2s seem to be very heavy on the battery when the ignition is o . Mine would come up with that message occasionally. I replaced the battery, genuine volvo, and it improved a lot. I think they just run a relatively small battery which shows up at the first sign of getting old.

[Gold 'N' Brown]

So to bring this to conclusion, my original (Bosch) alternator was indeed the fixed pulley type and I've replaced it with a Lucas rebuilt unit of the same type from ECP. With their 20% discount offer the other week it cost me £90 (plus a £71 surcharge which I got back this morning when I dropped the old alternator off to them).

Now got a healthy and pretty stable 14.3 volts showing with engine running. I meant to check if the battery had a date stamp but forgot. It's a genuine Volvo battery so would be quite impressive if it's the original 16 year old one. It charges and holds charge fine, starts the car fine, and has done an admirable job of keeping the car going seeing as how the alternator has been slowly on it's way out for quite some time and the battery has obviously not been at a full charge in a heck of a long time.