Hi. First post here, hopefully someone can help. I've got a 1988 B350 (Xplorer 228 motorhome conversion) with a cruise control problem. When I engage the cruise, it immediately loses 5 MPH (which I expect), then it slowly loses even more speed...about 1 MPH per minute or so. Is this a vacuum leak? Bad transducer? Where can I start to troubleshoot this? Thanks.

 

Factory cruise or aftermarket?

 

Factory cruise. Thanks.

 

There are no adjustments on the factory cruise like on aftermarket ones. This kind of leaves you out of luck and are left with only one option, replace the cruise control module. I don't expect you'll find a vacuum leak, because with a vacuum leak the cruise either works or it doesn't. In your case with the loss of speed, it sounds like electronic components within the cruise module have gone bad.