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>Gentlemen-I would like to trouble shoot/repair the cruise
>control on my 1990 V8. The documentation I have shows there are
>four parts involved:        * switch (on steering column)       
>* control unit (behind dash on passenger side)        * vacuum
>control motor        * vacuum vent valve brake switch The dealer
>said that the control unit is bad, but he hasn't been correct
>about anything yet so I don't want to spring for a new control
>unit until its been properly isolated.     Questions:        1.
>Where is the vacuum control unit located? 

On my car (91 200q), it is located on the driver's side inner fender,
behind the coolant expansion tank, I think. It has a vacum hose that goes
back to it. If you follow this hose, it goes to the little diaphram thingy
that pulls on thottle mechanism. You could locate yours by following this
diaphram that pulls the cable that pulls the throttle linkage, then find
the hose connected to it, then follow it to the vacuum control unit.

Look for cracks in the hose, and to check it for vacuum leaks, disconnect
it at the control unit, depress the diaphram at the linkage (so it's gonna
pull a vacuum on the line), then stick the line with a golf tee and put
pressure on the golf tee so it is less likely to leak. Watch the diaphram
for a couple of minutes and make sure it doesn't relax. If it does (I found
it hard to keep the golf tee from leaking), replace the hose or see if the
diaphram has a hole in it.

       2. Where is
>thevacuum vent valve located? 

I believe it is an intergal part of the vacuum control unit. I believe it
is just some sort of electrically operated check valve.

       3. Can I access the control
>unit without removing the             top of the dash ie from
>under or thru glove box?

Don't know, if I you could, I probably would of, because then you can
troubleshoot the cruise electrically with about six tests from the
connectors. That is one reason why your dealer might not be right, because
he hasn't tested from these connections. (the bently for my car shows these
tests, they are all either resistance or voltage or continuity checks).

         BTW, when I was replacing the
>frontright outside CV joint boot, my son (an ACE Porche Mech)
>was marveling at the UFO brakes on the left side and noticed
>what appeared to be some unconnected wires. These were visible
>looking directly at the engine from the wheel well. We fished
>them up from the engine compartment and they look like they
>mate. I did not connect them because I recall reading a listers
>admonition to resist the temptation. Unfortunately, I lost my
>saved E mail in trying to upgrade my ancient MAC to AOL
>3.0(20Mhz wouldn't hack it and all files were lost in the
>regression ).

Does changing the CV boot correspond to the cruise control not working? If
so, these wires could have something to do with it.

>      * 4. Are these lose connectors (pair male&female) located
>on the left side of the engine towards the firewall for test or
>could they be the reason my cruise control doesn't work?

See above. Need to test, dealer hasn't tested from ECU connections

>Your collective  wisdom on any/all of the above will be greatly
>appreciated.TIA and MERRY CHRISTMAS!!!

My cruise control stopped working after I changed some water hoses and the
crankcase breather hose which runs on the back side of the block. I checked
all the things above and did some road testing of the pedal switches by
pulling them back, but with no sucsess.

My cruise control started working intermetitently a couple of months ago,
now it works just fine all the time. Maybe because I didn't want to go into
the dash. One could only wish.

HTH, if you want more specifics, just ask.


Paul Waterloo
Brookfield, IL

91 200q

EMAIL: 74543.407@compuserve.com