Volvo Repair: 1994 850 Turbo Wagon - cruise control, cruise control system, vacuum pipe

Question
Hello!

I've always wanted a Volvo Wagon.  :)  Finally, at 33, I broke down and got one.  It's got just over 100k miles on it but has been well cared for.  But, to my problem (I actually have two and will submit two different questions).

My cruise control doesn't work.  Self-test shows no faults - either in the after-drive test (I get 1-1-1) or the component-only test (all components check okay).


The tube from the pump to the interior holds a vac seal fine via when sucked on.  Sucking on it moves the throttle and it keeps pressure, so I presume that the backend part of the system is fine.

The pump is getting only .75 volts on my meter.  I replaced the relay with one from the junkyard today and it did nothing - same voltage and the pump doesn't kick on.  Either my original AND the junkyard relay are both bad (unlikely) or it is something else.  Fuse is fine, too.

I also got a pump from the junkyard.  BOTH my original pump and the junkyard pump do not create a strong enough vac to move the throttle when 12v is applied directly from the battery.  They make noise and do create a vac, but not much of one.

So. . .

1. Do I have a short somewhere else in the system since 12v isn't getting to my pump in the first place?

2.  Do I need to loosen my throttle so the vac can move it for when I eventually fix problem #1 and get 12v running properly to the pump?

Oh, lastly, what is supposed to be the proper voltage when the car is on and in park, idling, with the cruise "on."

I need my cruise!

TIA,
John in NH


Answer
I would need to consult the manual for fault tracing the cruise to be sure of the signals.there is more than just power and groun to the pump to make it work.there is a manual just for fault tracing the cruise control system.

most common problem is a bad vacuum pipe from the pump motor.the pipe gets a hole in it under or near the side of the battery tray near the fender.I would still remove the battery and tray and check the vacuum pipe.if bad just splice a piece of vacuum hose from the spot of the hole  to the pump.

also you could try adjusting the brake switch under the dashboard.it is the switch with a vacuum hose attached to it.adjust it so it is closed more when the brake is released.