Dave, I took the vocational progam through high school so yeah (switched to computers in college), I agree my '92 Jimmy will not generate 35 V, under normal circumstances. But that's the problem, car parts have been known to fail and cause the most unusual effects.

If I can decipher all the sensor signals as planned, I will be spending a lot of time and energy on this project. I've already invested time and money as it is. If a potential problem only has a 0.01% chance of happening and it DOES occur, I'm gonna be one very ******ed off person if I skimped on a $2 safety component. I can afford a zener, it's not like I'm trying to survive on a student budget living in the boondocks (although that doesn't seem that far in the past ).

I also have ZNRs and a few other types of surge/clamping devices on hand that I've ordered for other projects, I'm just not sure what rating I should use. But since the voltage regulator is supposed to handle up to a maximum of 30V, I assume it would be wise to use something that would start clamping at 15-20V. That way I'd stay away from pushing the voltage regulator to the extreme rating.

Robert