I'm in the process of swapping the body off of a '94 F-150 onto a '93 F-250 chassis. The '93 never had cruise control but the '94 donor does and I want to keep it. In this regard, I have ran into a little issue.

The infamous cruise control pressure switch on the '94 F-150 was located like most on the master cylinder above the port for the front brakes. The '93 F-250 has got a master cylinder with a larger bore and no port for the pressure switch. Due to the difference in bore size, I can't just use the master and booster with the switch port off of the F-150. I checked with the parts store, and they don't show a master for the F-250 that has the correct bore size and a port for the switch, so I can't just go buy the right one. There's nothing wrong with the one that I have anyway.

For some unknown purpose, the F-250 does have a factory tee fitting attached to the frame in the the line for the REAR brakes between the master and the ABS valve. One port of this tee is plugged. The port is the same flare size and type as the cruise switch, so I just screwed it in there and considered the problem solved. But now that I'm thinking about it, I'm not so sure this is the correct solution. The switch was originally located in the master in a port tied to the FRONT brakes. Here it would have been exposed to actual hydraulic line pressure at all times. Where I have it now in the REAR brake hydraulic circuit, I believe that it is downstream of the residual pressure valve in the master for the rear drum brakes and that residual pressure might keep the switch made up all the time and not allow my cruise to work.

So here's my questions: Does anybody have an F-250 of this vintage with cruise and if so, where is the pressure switch located? Is there a residual pressure valve in the master for the rear drum brakes or is it incorporated in the ABS valve? If there is, do you think this residual pressure is enough to keep the switch made up?


I really want to get this right the first time because I HATE bleeding brakes. I can put a tee for the switch somewhere in the circuit for the front brakes if I need to, but it's just so dang convenient to just screw it in to the unused port in the rear circuit. Thanks for any help!

 

FWIW, if you don't mind losing the redundancy that that the switch provides, you can just jumper it....

Steve

 

That's what I would do, the older trucks like mine don't have the switch.

 

This probably won't help much... But I do remember working on a truck where I swore I saw the switch down there where you put yours. I don't remember the year or model though, but I'm curious now and I'll keep an eye out for it.

I do know for a fact that the newer F-250's (96 for sure) have the switch on the master cylinder. So if nothing else, maybe a newer master cylinder, if the bore size is the same, would work.

 

This doesn't exactly answer your question, but...

My 93 F150 has the pressure switch at the frame rail similar to what your describing.

Maybe someday I'll be able to get the new recall pressure switch installed

I'll take a picture if your interested.

 

Thanks for the input, guys! I've been scrounging through parts catalogs and looking at underhood pictures of trucks on fleaBay doing a little research. Near as I can tell, the pressure switch was first installed on the master cylinder on all light F series trucks in 1994. When I was looking for a master cylinder before, I didn't think to look it up for any year besides the '93. I haven't found any pictures of the frame rail area where I found this factory tee on earlier models, but at least now I have two sightings of the switch in this location. I also noticed tonight that there is an unused wiring pigtail clipped into a blank plug attached to the frame rail in the vicinity of the tee. I pulled it out and took the cap off and it's the correct connector and wire colors for the cruise pressure switch. It sounds like I guessed right. I'm going to go ahead and try it. Worst case, I'll have to replumb it if it doesn't work.