1990 Cadillac cruise control quits then comes back (not blowing fuse)

SOURCE: 1995 Cadillac concour crusie control will not turn on light for the cruise dont even come on

check the wiring to the servo. i hade the same problem . it was my wiring was bad. also check the fuse under the hood ign3

SOURCE: 1991 Cadillac Sedan DevilleI replaced

On the 91deville there is another relay box under the passanger side of the dash

SOURCE: how to fix the cruise control - won't hold speed

It is vacuum operated. It may currently be disconnected from the carburetor'throttle body linkage.

On the off chance it is connected, it likely has a hole in the diaphragm. So it may be disconnected at the vacuum line to the intake manifold.

There is also a vacuum dump switch which might be stuck open, damaged, or just out of adjustment which is normally pinched off until the brakes are applied and the switch is supposed to dump within the first inch of travel of the pedal. This is a mechanical override of the cruies control, and the brake light energy is supposed to release the control when the brake lights are energized.

There is also a magnet and sensor down either on the transmission speedometer gear housing,where it enters the transmission or on the driveshaft. If the magenr is not there, there is no speed pulse reference for the control to operate from. So it has no reference it can maintain.

It is not a sophisticated system, and it is prone to leaks after 23/24 years.

You can hear the dump valve if it is open, you can hear and see the diaphragm on the cruise control to see or hear if it is damaged when the hood is open. With the right meter, you can ascertain if the magnet is still present in the spot it is supposed to be once you locate the connector for the sensor- it is a hall effect switch usually.

You already know the electrical portion of the system works, so the problem is largely isolated to a vacuum leak or a sensor of unit is still connected. Normally the vacuum unit sits on the inner fender on either side.and the control cable arcs over to the transmission linkage side of the carburator or throttle body, it has one wiring harness connector and one vacuum connection and the cable to the carb, and usually only 2 bolts holding it down.

A wrecking yard might be a source for a good unit used, New old stock may still be in the system although likely aftermarket with the nationalization of GM.

Testimonial: "Thanks for the thorough answer! I will check those out and provide more details if it looks like there's something else."

SOURCE: cruise control is inoperative

It can be faulty cruise control switch. If the switch is replaced, then it can be wiring issue or faulty cruise control board. But as the switch is replaced, get the voltage at the switch tested to confirm the switch is actually receiving voltage. If no voltage received at switch power supply wire then, apply external 12 volt power to the cruise control switch wire and then see if cruise control comes ON. If yes, then you know wiring is issue.

On this case, to troubleshoot this problem, there are solved help links. Click the link directly and refer the details to solve this problem yourself, with help of diagrams: ------

CRUISE CONTROL
http://alltypesofpartsreplacing.blogspot.com/2012/12/cruise-control-not-workingcruise.html


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These will help.
Thanks.