zachtyler

I know there are a few threads like this, however I felt I needed to clearly detail my issue. I just had back surgery so I had my mechanic buddy help me with this one. He got the WJ booster and master cylinder installed on my 1989 Renix XJ. Brakes work great. However, we are having a hard time with the brake light switch. We even tried a new one. Didn't change much, got a bit better, but no complete fix. We ground the rod down as instructed in the various write-ups. We did not use a .25" spacer or washers between the booster and firewall. We just notched out the pinch seem a bit for clearance. The pedal is a little higher than the gas pedal, but doesn't feel like a big issue. Would that make a difference? Today we must've taken the booster off 7-8 times and tried messing with the rod more. Even welded on some more material since we were afraid we ground down too much. As it sits right now, the lights don't want to come on unless I press down pretty hard on the pedal. Even then, it's pretty finicky. Does this indicate any specific problem we should address? Trying to picture how the switch even functions, does it just press directly back and compress the spring? Or does it rotate/rock a bit? Is there any advice/tips you can give when it comes to how the switch should fit on the rod? Should there be any movement at all? Should the spring be slightly compressed in order to get the retaining rod through the hole? Sorry for all the questions, just trying to get some ideas as we aren't totally sure what direction to go.

TwistedWrench

The later XJs have a plunger style switch, but iirc the early ones had the rocker style switch, much like the old mustangs, etc. If so, yes it rocks and compresses the spring on one side. The brake pedal rod should be kinda squared off on the back, where it contacts the switch's rocker pad.

Check the switch for play. It must be tight, no side to side or front to back play. This is what the bushings/washers are there for.

Other possibility, the spring is just to stiff for your newly softened pedal. Ive run into this on the old mustangs when upgrading to modern power boosters. I just swap in a foxbody switch, as the use a lighter spring. Unfortunately i dont know what switch youd need to swap for your application.

bad_idea

On the Renix jeeps the brake switch presses up against that flat spot on the booster rod when the brakes are applied. The distance from the flat to the center of the rod hole needs to be EXACTLY the same as the old one. I ground too much off of mine. Switch would only work when slamming the brakes. Shimmed it with a chunk of coke can. Slice a piece of the coke can the width of the switch contact area and twice as long as the flat. Bend a 90 a quarter of the way down the 'shim', slide it between switch and flat spot, now bend the other end of the shim to capture it in there. Should fix your problem. Fixed mine. Been rolling strong for two years now.

Trick I picked up for grinding the flat spot: cut the end of the rod off of your old booster, clamp it to the new booster, grind the new one down to match the old one. Takes the guessing out. Considering you have already ground it, that ship has sailed. But may be useful to cut your old one and compare it to the old one to see where you are at.

zachtyler

Thanks for the information. Yeah we actually welded on a bead just to get more material on there to start over. We just can't get it right. Maybe a caliper on the old one between the hole and flat edge, and grind the new one according to that measurement. I'm trying to picture your coke can trick. So you slid in the piece of coke can when the switch was attached to the rod, correct? I'll have to try this before taking the booster out again.

zachtyler

I just went outside and I can get under the dash and I can move the plate on the switch just a tad and hear the relay engage. However, when I press the pedal there is no movement on the switch. I just don't know if that means I ground off too much, or not enough.

bad_idea

Coke can goes between switch and rod, with switch installed. I THINK (read guessing) that if you had not ground off enough material the switch would be engaged at all times.

cruiser54

Is the pedal to booster hardware installed correctly?

zachtyler

Hey Cruiser, glad to see you here. The one thing that we don't have is the pieces labeled "bushings" on the bottom picture. Mine is an auto by the way. The only thing we have is the two plastic spacers and the sleeve. When we install the switch on the rod, the sleeve goes thru and the plastic spacers on both sides. I'm not sure my mechanic still has the bushing pieces. I recall in a write-up that somebody did say to SAVE the small plastic sleeve/bushing. However, in the write-up there was only one. So, that goes in the booster rod and the switch fits around it. I do not have that, will have to find one. Last night I crawled under and I can get the relay to engage by pressing down on the spring plate on the switch with my finger. But, when I was pressing the pedal, the switch doesn't show much movement, thus not compressing the spring or engaging the lights. Hopefully the lack of bushing is causing the issue?

Edit: Getting the sleeve in the hole of the new booster rod is quite a tight fit. Have to force the sleeve in, and then it is secured via the plastic spacers on each side. Perhaps opening the hole up a bit more to allow for a little play? I found a bushing online, however it appears to be for the upper part of the pedal, not where the booster rod connects. Crown #J3225981. I found a bushing from a mustang that also utilizes the same style switch HERE.

zachtyler

Thanks to Cruiser, I now realize I am missing the bushing that was on the old booster rod. I believe that the lack of bushing is preventing the switch from having any movement, thus not engaging the brake lights. Trying to find a suitable replacement. Might have to try my luck at the junk yard, unless anybody knows of a part number that would work.

cruiser54

Yup. And you have to drill out the later booster rod to accept the bushings.

zachtyler

Thanks! You have any idea where I can get one? Might have to try my luck at the junkyard, I suppose. There are similar style bushings you can buy online that come out of older Fords since they utilize a similar switch design. Not sure if it would be the same diameter, however.

cruiser54

Junkyard first. I may have some.

zachtyler

I'm going to go tomorrow and cross my fingers. I'll let you know if I find one.

bad_idea

I have an 89 in my backyard right now I am parting out. If you want to pay for the shipping, then I will send you the whole switch assembly still on the booster rod. I'll just hack the brake pedal and booster rod off with a grinder to fit in a small box. That way you will have it fully assembled to have a better understanding of how it should go together.

zachtyler

Just got back from the junkyard. No renix-era Cherokees, or anything close. However, I looked at a Ford F250 squarebody and it had the same style switch, so I took the bushing out of that. The outer diameter of the bushing is indeed 5/8. It should work, I'm hoping!