by Ed Young
Last November, the Valeo alternator in my 1988 Esprit died for the third time, with a hair under 90,000 miles on the car. Due to the ground work that several turboesprit list members (A tip of the proverbial hat here to Phil Harbison, Tony Grasso, and Eric Fournier) did, I decided to go with the substitute Bosch alternator this time. The Bosch number is AL49X and it is found on the following BMW's: E30...'86-91, E24...'86-?, E23...96-97, and E28...'86-88 (not M series cars). It's also used on some Audi vehicles, but the AL49X number should be able to get you the correct unit, it was the number that my local Bosch dealer used. Mine came with papers in the box that claimed that the Valeo and Bosch are interchangeable, and how either one (Bosch or Valeo) could be in the box. They are VERY similar, but there are a few minor differences.
According to Esprit Guru and Fellow Lotus Corps member Sanjay Vatuk: 'The Valeo was used 83-95.5 in the US. The '88- 92 book indicates a different 70A alternator was used on normally aspirated cars, but all others are listed as the same 90A part. Before '83 I have no info."
If the alternator in your Esprit is giving you some problems, and if it's a Valeo product it will give you problems... it's only a matter of time, I suggest you consider following the recommendations here......and DUMP the Valeo! According to one of the other people that has done this substitution, the Bosch unit produces more current and charges the battery even at low idle speeds.
The Bosch unit is slightly bigger in diameter than the Valeo, but not enough to cause a problem. I had to struggle a bit more than usual to squeeze it into it's place under the plenum. Since my car is Bosch injected, there is a bit more in the way than 1989 and up cars. The pivot bolt mount was virtually identical to the Valeo, however the adjusting bolt mount on the Bosch casing is considerably deeper requiring a MUCH longer bolt. I think I went with a 3.5" or 4" long bolt to give the nylock nut some threads to grab on. I may in future try and adapt the old special Lotus adjuster bolt to work with the Bosch. That special head sure made it easier to lock the position of the alternator. The distance from the centers of the two mounting bolt locations is a tiny bit further apart on the Bosch and again, shouldn't cause a problem.
The old pulley swapped, also with no problem. I did have to slightly massage the inner diameter of the collar under the pulley nut to get it to fit the shaft on the Bosch unit. In order to get the pulley set up in the right location so the belt will track properly, I only used one of the washers that was used on the Valeo unit under the fan and pulley under the fan on the Bosch unit when I switched them over. The other 'keyed' washer that was under the pulley on the Valeo, I put between the pulley and nut on the Bosch. You might want to measure the pulley position on your Valeo alternator to insure that you get it set up right on the Bosch.
The only thing that might be scary to some was removing the four long screws holding the casing halves together to rotate the back half 180 degrees. If you don't feel comfortable doing this yourself, any mechanic can do it for you easily. This rotation puts the wire terminals in a position similar to the original Valeo unit. In my case, the smaller alternator wire had been hooked to the Valeo using a spade terminal. To hook that wire to the Bosch, I had to solder a ring terminal to the wire, and get an 5mm .80 pitch (metric) nut to secure it.
