It is an A/C truck but its currently disconnected. I got a new check valve but it does whistle when i shut the truck off. It doesnt act strange,just shuts off and slows down.
The problem, as described above, wouldn't appear to be caused by - or related to - loss of vacuum to the servo. The fact is that the system initially seems to operate as designed, but - after a period of time - it suddenly and completely shuts down. The throttle snaps to the fully closed position and the truck slows way down. That scenario would tend to indicate a loss of input to either the control module or servo.
The servo's vent solenoid is designed to be de-energized - which allows the vent valve to shift to the default (fully open) position if:
1. The brake (or clutch pedal) is depressed,
2. The system is turned off at the control switch,
3. An open circuit exists in the system feed circuit or,
4. There is a loss of input from the servo position sensor.
1&2 would be considered normal operation, while 3&4 are just two of many possible electrically related reasons for a system shutdown.
On the other hand, a loss of vacuum supply to the servo would generally result in a gradual reduction of throttle opening and road speed.
My 83 c10 cruise control has a new servo, brake switches, no vaccum leaks detected. I checked the switch on the column and that still works. The issue im having is the CC works fine for about 15 minutes when I first drive the truck then it disengages. Would that be a bad controller module? Any input appriciated
After a system shutdown, what actions do you have to take in order to get the CC system to re-engage? That might give you a clue as to what the problem is.
Unfortunately, this sounds like you have an intermittent electrical issue. The thing about intermittent wiring issues is that, in order to locate the problem, you have to be in the "right place at the right time". This is especially difficult with cruise control circuits because the system won't activate unless road speed is at least 25 MPH.
Do a thorough inspection of all wiring and make sure all terminal connections are tight/clean.
You might want to start at the fuse block. The power supply for the cruise system will be a PNK/BLK wire plugged into one of the IGN switched sockets on the far left bank:
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The wiring diagram for 1983 C/K trucks with Cruise Master III:
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