Have you found a solution to this problem, My truck is the same year and has the same issue, I have tried all of the common sense stuff but I can't figure it out. e-mail me at lengle05@gmail.com if you know how to fix it.
The air blower and the cruise control are completely powered by separate fuses. It is possible that both have blown fuses.
There are several ways to fix the cruise control on your Mercedes-Benz depending on the problem with the cruise control. Make sure the fuse for the cruise control is not blown.
cruise control does not work when headlights are on
Cruise will NOT work if the speedometer has a problem
If the cruise control on your 1987 300ZX does not work, you might have an issue with the cruise control fuse or wiring. You could also have a problem with the switch that turns the cruise control on and off.
E62 is a vacuum solenoid problem with the cruise control. E92 is a heated windshield request problem. E99 is a servo apply problem with the cruise control.
Many times this problem has been attributed to a faulty ignition switch. www.trailvoy.com All the answers for your Trailblazer from true enthusiasts!
I am having similar symptoms with my 99 Buick Regal. The blower motor will run all the time even with the keys out. When the blower isn't working neither will the cruise control. I have researched it and believe it to be the ignition switch. I have not replaced it yet, but feel that is the most logical thing. It's also possible that in your situation it may be either the Blower Control Module or a relay. However, it's likely the ignition.
If the cruise control will not engage, there might be a problem with the Electronic Fuel Injector or the MAP Sensor. There might also be a problem with the Oxygen Sensor. Some autos have more than one oxygen sensor.
According to the manuel... and what i found it's on the drivers side on the wall next to the door under the dash behind the cruise main switch. that's on a 1991 SE. my problem has been finding the diagnostic plug that is supposed to be next to the heater blower on the passenger side.
check the fueses check fueses
There are multiple things that can go wrong with the cruise control, you need to be more specific as to the problem your car is having. While traveling at highway speeds, the cruise control suddenly deactivated itself and would not come back on.