I've just got a quick question for y'all. The alternator is acting up on my 87 2.5 XJ. I have an 89 4.0 MJ with a brand new alternator. Will the 4.0 alternator bolt on my 2.5 with no issues? I'm thinking it will, but not 100% sure. Thanks

 

Look online. Search on any auto parts store website for each vehicles and compare part numbers. I'm gunna guess they're different

 

The part numbers are different, but the amps of the alternators is also different. I know the two I have here even have different part numbers, but my 2.5 has something like a 74 amp now, and my 4.0 has a 100 amp. But I happened to notice in my latest Quadratec catalog that the Mean Green alternators have the same part number for the 2.5 and 4.0, the only difference being that listing was for 91+, where both of mine are Renix.

 

I really couldn't tell you for sure. You willing to spend the time to take it off and see if it'll bolt up? I'd assume the 100 Amp alternator is a little larger in size. I can't say without a doubt though. It may require a little modification (grinding) but I dunno

 

Without really knowing, the higher output might only have different windings in the same case. I'd hazard a guess if it, and the connectors look the same it will work. Later they went to having the regulator in the (PCM) ....

Not sure though.

 

Yeah, I'm willing to take it off and try it, I was just wondering if anyone knew for sure. Between the rain we've been getting, and limited time after work, I haven't really had the time to try to swap them yet. I'll try it in the next day or two, and let y'all know if it works though, just have to get the time to do it.

 

Yeah I would think if the connectors on the backside are the same, it'll work fine. So compare the two and go from there. Pretty sure the connectors were the same through 1990 (when they changed to the HO in 91), so you should be fine

 

Btw, my voltage/alt is the first place I "feel it" if my belt is loose. Radi had a great tip. (I'm adding) Start it cold and turn everything you can on high. Run it a minute or two. Shut it off and see if the Alt pulley is hot. It should warm up pronto if its slipping.

I haven't actually tried it, but I know if I rub my hands together they warm up!

 

The belt isn't slipping, I know that. It goes from undercharging to overcharging, and won't charge the battery enough to crank it back up unless I jump it off.

 

Well, OK. I thought the test is easy enough. Huh...it does have an internal regulator, and if it's over charging I suppose you might suspect that! (the regulator). I'm not positive. Cruiser once posted, "do you have voltage at the yellow trigger wire on the alt". I only mention that because I don't happen to know where the regulator sences the voltage. I'd assume it would be right at it's output, but just don't know.

 

From searching they both appear to be cs130 but there clocked different. If there the same you can swap front covers . 87 2.5 on left 89 4.0 on right.

 

The first two minutes of this vid shows how front covers come off .Except DO NOT remove armature leave it in alternator .Screw nut back on ant tap on it so covers come off.