Thread: sdv6 alternator failure

Originally Posted by DiscoJeffster

I don’t suppose pretty please you have the part numbers for the overrun pulley and tool per chance?

I will dig up my eBay purchase history

Originally Posted by DiscoJeffster

I don’t suppose pretty please you have the part numbers for the overrun pulley and tool per chance?

One of these pulleys JAGUAR XF, LAND ROVER RANGE ROVER SPORT / DISCOVERY III, 2.7, D / TD – Alternator Freewheel Clutch – INA: 535019710 | | Car Parts and Accessories
and a 17mm internal hex impact NULINE OVERRUN PULLEY OAP REMOVAL TOOL 17mm Hex Impact Rattle Tool OAPT002 | eBay

Thanks!

Can I ask a dumb question please?

How does the overrun pulley work and how's it supposed to help? If it's being driven by the engine all the time when does it overrun? Given the load on the alternator will make it break instantly the throttle is released even if allowed to freewheel, I'm struggling with the concept to be honest.

Not sure what causes failures of the alternators in these vehicles - I'm guessing the way they are mounted or something putting strain on them? No idea really, just guessing as it isn't an issue in 99% of vehicles built in the last 4 decades is all.

Not trying to be a smartarse, just can't figure out what they do is all.

The alternator rotor is not a gyroscope,, there are electrical forces opposing its rotation.
If the engine slows, the rotor will corospondingly slow.
I thought the D4 already had a fuel saving process where it only charged on deceleration? (yes? no?)
so when maximum charging occurs you expect the alternator to freewheel?

The over-run pulley is to prevent the alternator from applying momentary extra load on the belt during high rev gear changes. The alternator certainly will not slow as quickly as the crankshaft does.
Note that the 4.4 TDV8 which uses a fixed pulley is fitted with a stretch belt.
The main rectifier diodes in Denso alternators fail over time due to high current, high temperature usage.

Is this momentary load is applicable to all pulleys on the belt Graeme?

Originally Posted by Pedro_The_Swift

The alternator rotor is not a gyroscope,, there are electrical forces opposing its rotation.
If the engine slows, the rotor will corospondingly slow.
I thought the D4 already had a fuel saving process where it only charged on deceleration? (yes? no?)
so when maximum charging occurs you expect the alternator to freewheel?

The way it was explained to me by a long time mechanic who now works for a large manufacturer of alternators is that the over run pulley is to smooth out the load on the serpentine belt caused during gear changes on "not as smooth" engines like V6s - he explained that these engines are more likely to jump the belt, so the pulley even out the belt load.

Also, the D4 alternator charges whenever it needs to - the regenerative braking feature is where it adds extra load to the engine by increasing alternator output whilst braking/engine braking