RWD - brake pedal height and brake light switch adjustment with booster installation

Volvo RWD 900 Forum

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brake pedal height and brake light switch adjustment with booster installation 900

Bending the brake pedal bracket to get the brake light switch to work properly is incorrect. There are adjustments.

The yoke that attaches the booster push rod to the pedal is threaded for adjustment to make for the proper pedal height. I imagine the yoke got turned in during your booster overhaul. There is an adjustment spec. As I recall, with the pedal disconnected, you measure from the far end of the yoke (or the center hole of the yoke, I can't remember) to the center of the where the pin goes on the pedal. I don't have the service manual and it's not listed in the pocket data reference, but from notes I've found on-line it's something like 1.8". You may be able to adjust it by turning the rod within the yoke, but I rather recall doing it by pulling the booster back out a bit to be able to turn the yoke on the rod. For those with a manual trans, the clutch and brake pedals are to be set at the same height. You didn't list your 940 model and year. There are different boosters for NA and turbos in the 700s/900s, but the yoke-pedal adjustment spec is likely the same for both.

Presumably you didn't change the push rod protrusion into the master cyl end, but that would also affect brake pedal height. That's also adjustable and should be checked whenever you install a new/rebuilt booster. Using a depth gauge or suitable short rod, you measure what would be the clearance between the end of the push rod and end of the master cyl shaft. As I recall, you loosen a lock nut and turn the push rod to adjust it. Notes and specs are in the 700/900 FAQ. There are different specs depending on year and presence of ABS.

There are also two different brake switches used with 700s/900s. The early and traditional style is adjusted with jam nuts on a threaded shaft. There is a spec for adjustment (something like 8-14mm of pedal travel before the lights go on), but trial and error works well, just don't set it anywhere near the threshold so your brake lights flick on going over a bump. The later style (1994-1995) is a tab mounted rectangular black plastic switch that is supposedly self-adjusting. Once mounted in place, you push and hold the pedal down, extend the switch by pushing the housing all the way out (click-click) then let the pedal come back to set the proper switch extension (you can pull the pedal back harder to get an extra click and a bit more brake light sensitivity). That later style switch is a real pain to remove/install -the mounting tabs are quite stiff and difficult to push in, you can't get your hand in, you're working half-blind (use a mirror if needed), the plastic tip can jam to the side of the pedal and break if you're not careful, knuckles easily get skinned, totally frustrating.
Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now


New ANSWERED brake light on [900]
posted by  volvo426  on Sun Jun 23 01:14 CST 2019 >

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