Looking back through years of posts there are several answers for specifications for alternator for Automatic and Manual transmissions. Attached appears to be a technical sheet showing and describing that the standard pulley (S6 Type) is fitted to automatic transmissions and the clutch pulley (SC6 Type) is fitted to manual. That said, not all posts agree. Also, looking at aftermarket websites, and even sales of used alternators, there seems to be much disagreement. Fast forward to current day and I'll pose the question again: What is the amperage and pulley type for X-Types for automatic and manual transmissions, and does anyone have experience with aftermarket (e.g., Bosch) replacements? Consensus going back from around 2009 to about 2021 seems to be 120 amp standard pulley (S6) for automatic and 100 amp clutch pulley (SC6) for manual. Really need to get this right. Appreciate comments.

 

Mahalo for finding the Forums. Lots of good information here that I think you will find invaluable. We pride ourselves in being a better car group. As part of this, we like to get to know what another. So, please stop by the New Member section and tell us a little bit about yourself and your kitty. This will give you a chance to learn who the movers and shakers are here on site.

As for your question, I am pulling my information straight from the service manual for the X-Type put out by Jaguar. So, if that is not a good enough source, not sure what to tell you. The petrol/gas engines (the 2.0L, 2.5L, and 3.0L) all use a common 120 amp alternator. This alternator uses a charging process that raises the battery voltage up to 15.3 VDC (max) to get a 5 amp charging rate into the battery. As the electrical load is raised and the alternator gets warmer, this voltage is lowered and will ultimately settle out at 13.6 VDC. This system will also compensate for the initial pull from the battery and replace that while the voltage is raised. The diesel engine uses a different alternator (as the mounting torques are different and it uses a different charging philosophy). The service manual does not specify the output of this alternator. I also know that there are different alternators used in the X-Type. So, I feel it safe to say that the diesel variants use the 100 amp alternator vice the 120 one.

With this being said, a 120 amp alternator may be fitted with either of the pulleys as it is dependent on the transmission, not the engine. Same can be said for the 100 amp alternator. So, you have 4 potential alternator/pulley set ups: 1) 120 with fixed pulley, 2) 120 with the slipping pulley, 3) 100 with the fixed pulley, and 4) 100 with the slipping pulley. Most alternators I think you are going to find will have the fixed pulley as this is the more common setup that is out there (especially in the US). With this being said, the pulleys are interchangeable. I can use the slipping pulley on an automatic transmission X-Type. This is not going to affect anything. Kinda like you can use the fixed pulley on a manual transmission vehicle. The downside to this setup is additional wear on your accessory belt from the alternator using the belt to help slow it down from rapid engine RPM changes. Does this mean it will kill a belt in months? Not seeing any big warnings or other similar notes, I feel this wear is minimal and would shorten a belts life by say a month after 5+ years of use.

Is there something that you are attempting to do that raises this question? Maybe we can get to a good answer by knowing what is leading to the question about alternators.

Aloha.

 

Much Mahalo for your answer! Very detailed and very informative. I had an alternator failure and was looking at my best options for a replacement. In researching the various alternator types I kept running across often contradictory information regarding pulley types. Was also interested in amperage, and whether there were any restrictions on amp output of which I should be aware. I just settled on and purchased the fixed pulley and upgraded to a 200 amp output. I chose the high-performance amperage output because many recommended and were pleased with the result. Again, thank you for the very informative information. Aloha Nui.

 

rmannyb, just a caution on the upgraded alternator. Our kitty does not like something that is not stock. I cannot explain it. If others from this site have had good luck, then I would put some faith in that. If you are getting word from people that have put this manufacturer into other brands of cars, do not be surprised if you still have issues. I have seen too many horror stories about people trying to replace an alternator in these cars and spending lots of money on something just to find out it doesn't work in the vehicle. This is why a lot of people recommend getting what you have rebuilt with Jaguar pieces. HOpefully what you got will do what you need. I always felt that a 120 amp unit was a little on the light side for all the electronics that the car has.