how many amps is my alternator i have a 1986 cadilac deville 4.1L

should be 120 amps

There may be two different listed if the heated windshield was available as an option in 86 (it was in 90 but I don't know how far back it goes). Fairly rare though, I don't think I've ever seen a post from somone who has one.

If the alternator is original, then the amp rating is stamped into the case. Should be 120 with rear defog, 100 without rear defog. Sometimes you can see the stamp, other times partial removal is necc. You will see a casting number then a space and either an 80, 100, or 120 stamped in it. If its a rebuilt the numbers usually disappear because the case is sand blasted for looks during the rebuild.