[V8] Cruise control under control
m35a1 at juno.com
Sat Aug 20 22:34:50 EDT 2005
Well, I got it working.
Got a tip from Tony that the control unit in the engine compartment is
actually an electric vacuum pump. Don't understand why they just didn't
use engine vacuum, but gotta deal with it.
Tried to get it to run---no luck. No power at the connector plug. Took it
off the car and onto the bench.
I took the top off the housing of the control unit and studied the
wiring; wired it direct and it worked, so that was not the problem.
Went under the dash and starting checking power at all the wiring. Could
not get power to the plug for the control unit at all. Then read the
owner's manual which says that the cruise only works when the car is in
drive going at least 22 mph. Well, that would be kinda hard to do,
sitting in the driveway.
Then I checked the wiring at the switch on the brake pedal. There was no
continuity across the switch, meaning that the switch was open. I thought
that would be normal, as a brake light switch is normally open, and
closes when the pedal is depressed. But it did not close when the pedal
was depressed. Something's amiss here. I checked the vacuum portion of
the switch. With the pedal at rest, the vacuum switch vented to
atmosphere, same when the pedal was depressed. Logic says that something
should change when the pedal is depressed. So I took the switch off. It's
function is that the electric switch is normally closed and opens when
the pedal is depressed, and the vacuum is normally closed and opens when
the pedal is depressed.
I discovered that the switch was not screwed in far enough for it to stay
closed at rest and open when the pedal was depressed. I tried screwing it
in further but it kept popping back out.
Turns out the the plastic grommet that the switch is screwed into had
broken and it would not hold the switch in place properly. I found a
large nut to fit the threads on the switch in my pile of goodies. I
replaced the switch into the grommet then screwed the large nut onto the
switch behind the plastic grommet so now the switch can be held in the
Now the cruise is working again.
That explains why folks don't usually get stuff like this fixed when it
breaks. I spent 6 hours diagnosing, researching, repairing and testing.
With shop rates in the $150/hr. range, that's $900 to get the cruise
Not like I'd pay that kinda money!
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