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 Topic: troubleshooting ’80s sears autocruise ( Topic Closed)
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jumpjg
Joined: June 17, 2010
Posts: 1 |
| Posted: June 17, 2010 at 1:20 PM - IP Logged |
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New Member, first post. Thank you for the opportunity to "pick your brains".
I am refurbishing an old car (1965 Volvo) and have been updating many systems, one of them being the installation of a cruise control. I purchased a NOS Sears Autocruise that I believe was manufactured by Dana and marketed during the early '80s. It uses a driveshaft pick-up coil, an ignition secondary pick-up, vacuum servo, and the "purple box" with trimmer pots for adjusting pick-up speed, centering, and sensitivity. I have the system installed per the installation manual and all electrical & mechanical systems seem to be functional, but I'm unable to get normal operation - hoping to gain some insight here.
First off, I should mention that the car is not road worthy yet so all of my testing has been done with the car on jack stands. I'm hoping that my symptoms may be due to operation without any load on the engine - keeping my fingers crossed.
The symptoms: When I press & release the set speed button (~35mph as per the speedometer), the servo does not take up slack in the linkage. If I slowly let up on the throttle, the road speed will slowly drop, then the servo will pull the throttle open. Since there is no no load on the engine, it instantly revs up to like 45 mph, then drops off line. If I set the speed as above but hold the throttle steady, then actuate the accelerate/resume switch I get the same response. I have adjusted the trim pots some but I have not been successful in getting the servo to take the throttle from me without getting into the overspeed condition where it falls of line, which I believe is a built in safety feature.
Actions taken: Double checked all connections/ground for correct hook-up, followed the electrical check-out troubleshooting procedures included in the installation manual, double checked the clearance between the driveshaft pick-up coil and the magnet (spec = 3/4" to 1 1/4", set at low side), checked operation of pot on the servo (nominal), checked for vacuum leaks in hoses and servo diaphragm, checked operation of charge & vent valves on servo, checked electrical connections between the harness & the control box. All checks reveal no anomalies.
I would appreciate any insight that someone might have concerning this system. Thanks for your time.
Joe in St Louis |
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91stt
Joined: May 24, 2006
Location:
New Jersey,
United States
Posts: 488 |
| Posted: June 17, 2010 at 3:32 PM - IP Logged |
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The only thing I can think of is that the lack of load is causing an erratic vacuum supply/signal and giving you poor response.
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This information is provided only as a reference.
All circuits should be verified with a digital multi-meter prior to making any connections. |
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sparkie
Joined: November 06, 2003
Location:
Canada
Posts: 1,806 |
| Posted: June 20, 2010 at 2:12 PM - IP Logged |
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You can't check a cruise with the vehicle on jack stands other than to know that it engages when pushing the set button. You must road test the vehicle. The magnet should only be about 1/2 inch away from the head of the bolt that goes through the pickup coil for the road speed sensor. Make sure that the sensor is securely mounted and won't be affected by up and down movements of the drive shaft. You need to keep the distance between the sensor and the magnet constant even while driving over bumps. Set the trim pots in the middle of their range and adjust them while road testing. Sensitivity set to middle. Set the low speed one first and then the centering one. Make sure to use a good vacuum source or add a vacuum reservoir if needed. Make sure your cruise is grounded to a clean, paint free area of the body. There should be no slack in the cruise throttle cable. If there is a over-rev on a spark plug, make sure it isn't closer than a few inches to another plug wire or coil. You can check all these things before you road test, but you will never get to test the cruise until you drive the car and have the drivetrain under the proper load.
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sparky |
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howie ll
Joined: January 09, 2007
Location:
United Kingdom
Posts: 9,709 |
| Posted: April 01, 2011 at 2:12 PM - IP Logged |
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Sparkie, a correction I think, you probably CAN test a vehicle that old on a stand, a modern vehicles anti slip would probably prevent the driving wheels even turning.
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Amateurs assume, don't test and have problems; pros test first.
Read the installation manual, do a search here for your vehicle wiring. |
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