Cruise Control Freakin' Out

[Pomp]

This morning in a heavy rain doing 60 down the highway with the cruise on, the car started surging like every half-second. I cancelled cruise control and it stopped. I re-engaged it and it did it again. It keeps doing this accelerate-decelerate over and over every half-second. What's doing this?
Pomp

[benzboy87]

Mine is doing the same thing. Do a search under "cruise control amplifier" or "cruise control amp." - will give you lots of info.
BTW - I found out the hard way about using the cruise in heavy rain - totalled a brand new (three month old) S600 sedan because I hydroplaned. Needless to say the insurance company dropped my parents because of that one. I was very lucky to have walked away from it with only minor cuts, bruises, and a couple of broken ribs.

[Pomp]

I just drove it. It's not raining anymore and the cruise is working fine. Do your symptons come and go? Or does it consistently work wierdly?

[benzboy87]

At first it came and went - now it is pretty much constant. I need to replace mine altogether (cruise amp.).

What was the temp. there yesterday? It could have an effect on the amp.