Frequent & Intermittent Cruise Control Failure

[GrandMa]

<!--StartFragment --> Car: 95 Mercury Grand Marquis
Issue: Frequent & Intermittent Cruise Control Failure
Specific: Often unable to engage cruise control for more than 1-2 seconds. As soon as "speed control" display comes on, it disappears from the dash board. Sometime it works perfectly for a while, then I disengage due to traffic condition then it won't able to engage again. Cycle the cruise ON-OFF/Set/Resume does not work.

Does anyone have troubleshooting ideas or know what is wrong with the unit?

[grampaws]

Do you disengage the cruise by stepping on the brakes.
if so brake switch could be sticking and not letting you
re-engage the cruise. I believe it is mounted on the
master cylinder.Some one with a test light or Ohmeter
could check it to se if it's sticking.??

[Richy04]

I notice driving behind Ford/Lincoln/Mercury vehicles that the brake lights flicker on and off, apparently they use a real sensitive brake light switch and if your foot is within an a s s hair of the brake pedal it will flicker on and off. My guess is like the above, get your size 14's EEE's away from the brake pedal and see what happens..

[larryo340]

from what I remember there is a dump valve under the dash that can go out of adjustment and cause problems.
Sorry, but I don't know how it is adjusted.

[grampaws]

I notice driving behind Ford/Lincoln/Mercury vehicles that the brake lights flicker on and off, apparently they use a real sensitive brake light switch and if your foot is within an a s s hair of the brake pedal it will flicker on and off. My guess is like the above, get your size 14's EEE's away from the brake pedal and see what happens..

This is true but usually the switch on the Master cylinder is the one
that terminates the cruise.The one that has the fire hazard recall.
the switches in the column can be defective sticking or a contact
problem at the contact ring under the steering wheel. the wiring
loop in the same location for air bags ETC can become defective..
You really can't go much further until you determine if the switch
inputs are actually working..removing the steering wheel would be
necessary or you have a diag. tool that displays the inputs..
both should be done by someone with experience in these areas..
The wire coil can be damaged removing the steering or the airbag
can explode if not handled properly.

[Advancedautosec]

This is true but usually the switch on the Master cylinder is the one
that terminates the cruise.The one that has the fire hazard recall.


fire hazard recall? care to elaborate on that?

[RCSignals]

fire hazard recall? care to elaborate on that?

That recall does not have anything to do with our cars

[RCSignals]

I notice driving behind Ford/Lincoln/Mercury vehicles that the brake lights flicker on and off, apparently they use a real sensitive brake light switch and if your foot is within an a s s hair of the brake pedal it will flicker on and off. My guess is like the above, get your size 14's EEE's away from the brake pedal and see what happens..

Well not quite that sensitive.
It isn't just Ford/Lincoln /Mercury vehicles you'll see brake lights flicker on and off. It's more of a driver problem, too many people drive automatics with their left foot always over the brake.

There is a thread her from some time back where a member was concerned his brake lights were not coming on soon enough.