1998 V70 Cruise Control Vacuum Pump

adman11 · Post by **adman11** » 16 Nov 2014, 15:43

I am trying to fix non operating cruise control and wanted to bench test the vacuum pump under battery tray. 3 wire plug (Blue/Blk, Wht/Blk and Green/Blk) Question is simply how to connect to 12v battery supply to see if pump itself is bad? Any help would be greatly appreciated. It's hard going 30mph in my driveway... thanks

Post by **polskamafia mjl** » 16 Nov 2014, 17:20

Bump.

I'm curious too.

Post by **Ozark Lee** » 16 Nov 2014, 19:20

Blue/Black to battery positive and common (Battery negative) to the Green/Black will turn the motor on. I would do that with the module unplugged.

...Lee

adman11 · Post by **adman11** » 17 Nov 2014, 07:12

Thanks, Lee. I'll try that to see if I have working pump. Do you happen to know what remaining wht/blk connector is for? thanks again for your help

Post by **Ozark Lee** » 17 Nov 2014, 07:57

The white/black wire controls the pump. The module tells it to turn on and how fast through the White/Black wire.

...Lee

Post by **erikv11** » 17 Nov 2014, 08:35

You can test the whole thing in place in the driveway, using jumper wires.

Download the manual from here: www.matthewsvolvosite.com/downloads/Volvo_850.zip

Unzip and in the file called cruise "control system.pdf" there is a series of tests you can run. The manual is written for a 95 but everything applies to the cruise on your 98 except the parts that use the OBD1 diagnostic box. I've checked out several post-95 cars this way, it works great.

adman11 · Post by **adman11** » 17 Nov 2014, 15:35

Thanks all for replies. With pump disconnected and on bench, I hooked up positive to blue/black and negative to green/black terminals on pump. Took cap off to look inside too. Pump tries to spin a tiny bit when connected but stops. The white/black connector goes to solenoid inside which clicks when power to it. Looks like pump motor is shorted and will try replacement. Thanks again and will keep you posted if that doesn't solve my problem.

adman11 · Post by **adman11** » 02 Dec 2014, 14:35

Ok, working pump installed, still no cruise control. Here's what I've done
1. Checked vacuum lines with pump disconnected from cc unit/connected to battery, pump works,holds vacuum, no leak at servo/brake switch/lines
2. Pulled stalk/selector switch
a. power to yellow/blue on harness
b. when switch ON, power to gray/white
c. when selector set+ pushed, power to red/black
3. Pulled Cruise control Unit under fuse box

adman11 · Post by **adman11** » 02 Dec 2014, 14:59

Didn't finish and hit send by mistake...
3. Pulled cruise control unit under fuse box
a. with ignition off, ground to 3S, got 1.3 ohms (not 0 ohms....)
b. with ignition on, ground to 1S, got battery voltage
c. with ignition on, ground to 9T, no battery voltage.....
d. with ignition on, selector ON, pushed SET+ and got voltage at 4T....
e. with ignition on, selector ON, pushed Set- and got voltage at 8T....
f. with ignition on, selector ON, pushed Resume and got voltage at 6T....

4. Brake/Vacuum switch has power going in and not exiting when brake not depressed

I don't know if I'm reading manual correctly, but it looks to me like manual says to replace stalk switch if you show voltage to 4T, 8T or 6T when relevant set or resume buttons pushed. Is that correct as it seems backwards??? Shouldn't voltage be present at those terminals when buttons pushed? The backprobe test on the stalk switch delivers momentary power to each of the relevant wires and if those wires are connected to 4T, 8T and 6T shouldn't those correctly be showing that same momentary voltage? As you can tell, I've spent far too much time in diagnosing what I had thought would be easy fix....

My pump motor is just not getting power to turn on

Any help or hints would be greatly appreciated...

Post by **phils94850** » 03 Dec 2014, 06:06

I went through the procedures as you were doing and got confused just like you. I decided to do some more research and found where a guy fixed his with a piece of double sided tape. I figured what the heck and tried it and it now I have cruise control again.

On the brake pedal you have two switches .. on my car the upper switch was the culprit. There is a plunger that sticks out and when your foot is off the brake pedal that switch should have current going through it. A lot of times the switch gets out of adjustment and it wont close causing your cruise control not to work. Take a piece of double sided tape and put between the plunger and the brake pedal ( closing the gap when your foot is off the pedal ) and see if your cruise works again. If not.. put a piece on the other switch there as well..