98 S70 cruise control not working

steveroof · Post by **steveroof** » 21 Nov 2012, 20:24

Hi everyone,
About 3 months ago I bought my first car, a 98 S70 GLT. My friend was getting rid of it just when I needed a car for a new job. Let me say that before I bought this car I never really heard of Volvo, but I think that along with the car, I also bought into a pretty cool community of dedicated owners.

Anyway, I knew the cruise didn't work when I bought the car, but I'm interested in getting it working.
My symptoms are that when I set the cruise to the on position, the "+" side of the "set" button on the end of the stalk makes noise, and I can feel a slight vibration in the gas pedal. The "-" side does nothing. The manual says that cruise doesn't work below 22mph, and indeed, when below 22mph the "+" side does not make any noise. This leads me to believe that
-the car knows what speed it's going (no noise unless above 22mph) and
-there is some kind of complete linkage between the cruise system and the pedal (hence the vibration)
-something may be wrong in the stalk (noise from "+" side but not "-" side)

Any thoughts would be appreciated.

Post by **rspi** » 22 Nov 2012, 03:54

Vacuum leak somewhere. You'll need to check your vacuum lines and repair/replace any bad ones.

Post by **precopster** » 22 Nov 2012, 05:48

There's a diaphragm near the gas pedal. Remove and check for a hole. A torx driver is needed to access the linkage attached to the upper part of the pedal bracket. The pump for the diaphragm is located under the battery tray.

Post by **cn90** » 22 Nov 2012, 05:52

1+,

Usually there are 2 culprits:

1. Broken vacuum lines.

2. The brake switch above gas pedal.
Kneel down and look up above the brake pedal with a flash light.
There are 2 switches: 1 for braking and 1 for cruise.
You may need to adjust the cruise switch.
I posted info on how to do it in the forum.

Post by **Volvoforlife2** » 22 Nov 2012, 06:58

You may also want to check the brake pedal position sensor. If it is bad then you wont be able to engage cruise control until its fixed.

Post by **rspi** » 22 Nov 2012, 08:56

I was about to say that I have had just about every cruise failure know but I won't, don't want to ginks myself.

Post by **erikv11** » 22 Nov 2012, 11:43

vacuum lines as suggested, specifically start by checking the rubber elbow on the cruise pump under the battery tray. It is usually the first cruise problem.

steveroof · Post by **steveroof** » 26 Nov 2012, 17:26

Thanks everyone. I tried resetting the switch by the pedal, it did not solve the issue. I depressed the brake and pressed in on the switch's plunger. It popped out, and then I let the brake pedal back to press the plunger back in.
Next I will try the lines beneath the battery tray. Is the battery tray easy to remove?

Post by **erikv11** » 26 Nov 2012, 20:55

You can actually see the cruise pump, and the offending elbow, peeking out from under the tray if you stand in front of the car. Or get the car up on ramps and look at it from below.

But yes it is easy to remove if you want to: Remove battery, remove tray, be careful not to stress out the vac lines on the attached cruise pump.