A 1995 850 sedan I recently purchased and will pick up this weekend has a factory cruise control unit that won't engage. Short of it being as simple as a bad fuse, what else should I be looking for before I break down and take it to my local independent Volvo service center?

Thanks in advance for your help....

*sigh*

The cruise control in your Volvo consists of several discrete components, and several major components. The major components are the controls (the switch and the button), the vacuum pump, and the ECU (Electronic Control Umbrella).

The vacuum pump is bolted to the bottom of the battery tray. I'd remove the battery, pull up that tray, pull off the vacuum hose (the one that DOSN'T just loop back) and suck on it while looking at the throttle drum. If it is difficult and the drum (eventually) starts to move, then the hoses and such are good, which is good!

My next step was testing the pump. The pump is really a pair of units... a motor and a solenoid. The motor creates a vacuum and pulls the gas pedal down. The solenoid releases the vacuum, and lets the pedal up. There is a valve on the brake pedal that also lets the vacuum out when you press the brake pedal.

I pulled it off an connected it to the yellow and black lines of an Apple IIe power supply. The motor ran, which was a good sign... however I was unable to get a vacuum with both of the "nipples" covered. I'm assuming this means my pump is bad.

However... to check to make sure it's not electrical, connect a pair of test lamps to the motor pins and the solenoid pins, and run them to the windshield so you can see them blinking while driving. Pressing SET with the switch ON should result in the motor running at least.

I'll be working on mine within the month, so I should have better documentation and of course... pictures.
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The most common problem is that the vacuum hose under the hood cracks from engine heat. It requires a "bandaid" on the hose.

However, if you get a good mechanic, have him reroute the vacuum hose so it doesn't lay across the engine block. Because it will happen again.

Because there are so many possible answers to your question -- look at the archives, searching under 850 cruise. Have fun.
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95 850, 88 245