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Not an easy fix, so I hope it helps others with cruise control problems.
Car is a '94 turbo convertible.
Problem was intermittent cruise at first, then no cruise at all.
This had multiple causes -- vacuum and electrical.
Started with more likely vacuum problem. Checked by pulling off line to pump and sucking on it. It would pull throttle in but not hold it. Replaced vacuum line from pump to the car interior, as it's end had swelled so much it wouldn't make a tight fit. Could have chopped off 1/2" and refitted, but decided to replace entire line to eliminate chaffing as a problem. Still wouldn't hold vacuum. Next, I replaced line to accel actuator under dash. Also took 1/2" of slack out of chain from actuator, which was reason for delay in SET speed catching on. Now throttle would stay for a minute, but still slowly creep down. Final vacuum problem was found to be leaking turbo shutoff valve. As others have posted, removed threaded part and applied teflon tape. Sucking on line from pump now pulled throttle and it stayed when I closed line with my tongue. Vacuum problems now solved!!
Still, cruise wouldn't engage, so I must have electrical problem. Cruise control is designed to shut off by both vacuum and electrical routes. Both must be operating correctly for cruise to engage.
As Townsend page suggests, I started by checking plug to cruise ECU. Their page is for earlier model with different pins so I had to adjust for my model. I'll post back with this information when I get more time.
ECU must see certain voltages and grounds from components or it will not operate. I initially thought of a bad ECU from reading other posts, but Jim Dewar, a local indie dealer, talked me into checking brake and clutch switches as these were more likely the problem than the ECU. These switches are in series and must have continuity for cruise to operate. If both are good, they allow ECU to see 12v on pin 9 (red wire) when key is in RUN, cruise is ON and both pedals are released. I wasn't getting 12v. Brake pedal could be checked easily and showed continuity. However, there wasn't room for leads from multimeter at clutch pedal, so I disconnected plug from clutch pedal and jumpered across it using a cutoff safety pin. This gave 12v at pin 9. All other pins were seeing proper voltages, so I knew the clutch pedal was bad. Confirmed this by test drive. With plug to clutch pedal jumpered, I had cruise! Hope this helps others fix their problem.
posted by 64.158.1...
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