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1966 Cruise Control problem

Started by Gary McKinney, November 10, 2012, 03:10:14 PM

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Gary McKinney

The cruise control in my 1966 Eldorado has always worked well, but yesterday as I was about to start the car, the cruise control started making a loud noise like a motor running (a very noisy motor!).  It does this with the ignition switch in the ACC as well as Run positions, and it does it with the cruise control switch in Off, On, and Auto.  Moving the Cruise Control switch between Off and On makes the sound stop momentarily.  Driving the car a short distance while moving the Cruise Control switch from Off, to On, to Auto didn't make the noise stop.  The noise is loud enough to be heard in the car while driving.  I unplugged the connector to the Cruise Control which, of course, stopped the noise.  Any ideas what's causing this and how to fix it?
Gary McKinney

1950 Cadillac Series 62 Coupe
1966 Cadillac Eldorado

cadillactim

Take the top cover off and look for a broken part. If you unplug the wiring and the noise quits, then it sounds like the motor is running when it shouldn't be, and something has broken, thus making the noise while the motor is running.  Tim
Tim Groves

Gary McKinney

#2
Well, one thing I learned is that the cover can't be removed with the unit in place.  I took out the four bolts and opened it as far as I could, but didn't see anything that looked broken.  Everything inside looks as new, probably has never seen the light of day.  I'll have to unbolt the unit from the bracket to completely remove the cover.
Gary McKinney

1950 Cadillac Series 62 Coupe
1966 Cadillac Eldorado

quadfins

It sounds like the worm gear (on the motor shaft) is no longer engaging the gear that connects to the arm that has the electric point on it. If the arm is at a location which would energize the motor, but the motor does not move the arm, it would run continuously, since the input that it is getting is telling motor to activate.

The receiving gear may have worn down, or the worm gear bushing may have shifted, allowing the worm gear to disengage.

When you have the cover off as much as you can, and you turn on the power, does it sound like the motor is running away? You would be able to very clearly recognize the sound of the electric motor running.

Jim
Jim Eccleston
1961 Coupe de Ville
BATILAC
Senior Crown
DeCou Driving Award x 4

Gary McKinney

I took the power unit (as the shop manual calls it) out and found that everything was connected properly.  The motor was connected to the worm gear, and the arm that's driven by the worm gear was all the way to the top.  It appeared that the motor was not, in fact, running, rather it was TRYING to run, resulting in that noise.  I'm assuming a set of contacts must have been stuck, causing the motor to try to operate.  So, I took the bushing off the top of the worm gear shaft to allow the shaft to separate from the motor shaft, then manually turned the shaft so that the arm was about half way, made sure the contacts were free,  then reassembled everything and the noise is no longer there.  The red indicator lamp illuminates when the switch is moved to "Auto," and goes out when the switch is moved to "Off."  The weather is not good today, so I can't take it out for a test drive.  I'll post more when I know more.
Gary McKinney

1950 Cadillac Series 62 Coupe
1966 Cadillac Eldorado

cadillactim

You might want to take points file and clean the points in the unit. Also, the grease in the unit may be acting like glue by now from age and causing parts to stick together. Really not that difficult to disassemble, clean, and reassemble the unit. If you have a shop manual it's pretty straightforward.

Tim
Tim Groves

Gary McKinney

The weather has been nice enough for test drives, so I've been working with the cruise control unit.  It no longer makes any strange noises, but it no longer operates correctly.  It will lock in and control the speed, but only at one speed, aprox 50 MPH.  Turning the dial has no effect on the speed.  I'm also now getting back pressure on the accelerator pedal, even with the cruise turned off.  I took the cover off and manually moved the  motor feed points, determining that the motor operates in both directions and drives the throttle arm.  I cleaned the contacts, lubricated the moving parts per the shop manual, and reassembled the unit, but it still won't operate properly.  One thing that I did notice is that the terminal block attached to the unit has, at some time, been broken, and an attempt was made to glue it together, but the repair has failed.  Could this be the root of the problem? 

In the event that I'm unable to get this thing to work, is there anyone who repairs these units? 
Gary McKinney

1950 Cadillac Series 62 Coupe
1966 Cadillac Eldorado

cadillactim

Gary

See if the speed dial is moving the cable. With the cover off, watch the shaft with the long spring on it. Have someone rotate the dial back and forth. You should see the spring/rod move as the cable moves. If it doesn't, then the plastic clip that the cable snaps into may be broken. That clip is is located inside the tube at the front of the cruise unit.

I do rebuild these units if you find that necessary. You can email me directly at tagroves@wctel.net, or call during business hours at 864-352-3306. 

Tim
Tim Groves

Gary McKinney

I checked the cable as suggested and found that it was connected correctly.  So, I took the power unit off the car (I think I can now do that blindfolded) and re-cleaned the points.  I noticed that the motor feed points looked like they were way out of adjustment, so I adjusted them per the shop manual, and, miracle of miracles, the thing works again! 

Thanks to Tim and Jim for their input.  And Tim, the next time that unit fails I'll be calling!

Gary

Gary McKinney

1950 Cadillac Series 62 Coupe
1966 Cadillac Eldorado

cadillactim

These units are pretty durable, and sometimes cleaning and adjustment are all they need. Glad you got it working.  Tim
Tim Groves