Here's my complete diagnostics for the cruise system, step by step:
STEP 1
Speedometer OK? All Brake Light bulbs in tact? Goto #2. Otherwise repair.
STEP 2
Test the cruise first on the road. Once above 30 mph, hit the cruise control stalk in the 'accel set' direction. If it tries to work, engages momentarily, then your problem is
most likely the cruise amplifier, see #3. If it does not work at all see #4.
STEP 3
You can send me the amplifier to repair if you'd like. My service fee is $60 + $6 for return shipping. I might have a unit in stock for your car. If I do, once your old one arrives, the repaired one will ship out immediately. If not, I'll repair the one you sent in and have it back to you within a weeks time. As a precautionary measure, you should check out the health of your cruise control actuator, see step 5.
STEP 4
Test the signals being sent to the cruise control unit. The cruise control stalk might not be working properly or your brake disengage might not be working.
FS: Cruise Control Amplifiers (Repaired)
If everything checks out go to #5, if not, you probably have to replace the cruise control stalk. I've not really seen many broken/bad ones but its always possible
STEP 5
Test the cruise control actuator and make sure the linkage is connected! As the cruise control actuator ages, it will tend to draw more current from the cruise control amplifier, there is a limit on what the amplifier can provide. Should the actuator draw past this limit then there is a good chance that eventually it will kill the amplifier.
Inside the box: VDO Cruise Control Actuator
If this checks out, goto #6, otherwise replace the actuator with one that tests out OK and start back at #1.
STEP 6
Well, if you've tested everything that I've said the only thing left to be faulty is the cruise control amplifier. Like I said earlier, I'd be happy to repair it for you, my service charge is $60 + $6 for return shipping. If I have a unit thats compatible with yours in stock, as soon as your old unit arrives, I will ship the repaired replacement out, if not I'll fix up the one you sent in and have it back to you within a weeks time.