Hello,
i have a snapped switch with the metal section stuck in the master cylinder. I also have a problem with the rear brakes over heating after about 20 miles, even though its had all new calipers, rotors and flexi hoses, could the 2 problems be related? Thank you. ( Robert Longford, 05/23/2022 )

Hi Robert,

    Without your VIN I am just guessing you have a W-Series Workhorse chassis based on the part you are asking about. I don't think the two issues are related, but you can pretty easily remove the broken plastic threaded end of that switch from the master cylinder to install a replacement.

    As for the rear brakes hanging up, where were the calipers purchased from? If you have installed calipers that are not from Workhorse then they do not have the correct bore diameter, and are known to do just what you are seeing.

    The calipers for your chassis look just like other calipers you can buy, but the ones that you need were modified by Bosch for Workhorse so they wouldn't do that. Here is a link for the calipers you need https://www.workhorseparts.com/W8007383-W20-W22-Brake-Caliper-Asm-(66mm)

    If you have already installed Workhorse calipers then I would look and see what side of the pads are hanging up. If it is the outside pads then make sure the guide pins are not tight in the bore and are well lubricated. If it is the inside pad, then I would attach a pressure gauge to the caliper and press and release the brake pedal a few times and see if it is dropping all the pressure when the brakes are released. If it is releasing all the pressure then you have a failed caliper, if it is not then it could be many things such as the master cylinder or brake booster and so on.

I had my RV in for brake repair. When I picked it up, I noticed the switch had been broken off during the repair. The shop claimed that it was not used because one of the wires had been cut before I brought it in. I can verify that that is correct. However, it broke off at the master cylinder. The threads are still in the body of the cylinder and a steel pin is stcking out. I read on your question page that the master cylnder will not leak and the pin sticking out is no problem. Should I just leave it as is, or get the shop to easyout the switch and replace?

My vehicle is a 2002 Fleetwood Southwind RV.

Thanks for your consideration
David Cole ( David Cole, 09/22/2021 )

Hi David,

    I would have that extracted, it is not too bad to get out since it is plastic. I have had good luck just driving a flat head screwdriver in there being careful of the threads in the master, then just turning it out of there. That switch warns you if your brake pedal is traveling too far, so you should have it operational.

My pressure switch broke off at the edge of the master cylinder. The metal rod is sticking out. The plastic threads are in the cylinder. If I do nothing will brake fluid lead out? If I glue the pressure switch to the
master cylinder will it still work? If I do not use it should I cap off the wires running to the switch? I'm afraid to change the switch because I don't want something to go wrong and have to replace the master cylinder. ( Patrick, 12/17/2020 )
Patrick, no brake fluid will leak out , if the contacts are in position glue may work. The switch is a safety item and we recommend keeping the brake system completely operational due to potential liability concern . 
i replaced the pressure switch and the brake failure light came and stayed on. i read previous answer so i went out to clean any debris and found none..now the question.how deep is the hole that the switch pin goes into? i have the threaded part,then a machined face and a hole in the middle of that and its only about 1/4-3/8 deep, it looks to me that master cylinder did not reset,is that possible?i have never had a brake failure light before. i have had abs light come on and then go back out 10 min later.other then that the brakes have allways worked good ( gregory BROWN, 10/21/2020 )

That master switch is activated by a groove in the rod inside the master, when that groove lines up with the switch the brake failure light comes on with the buzzer (if the speaker is not blown) sometimes that rod gets stuck and you cannot unstick it so you have to replace the master cylinder

 That groove lines up with the switch when the brake pedal goes down too far, like when you bleed the brakes

My w8000130 pressure switch broke off clean with just the pin sticking out of the master cylinder.

What is the purpose of this switch and what will happen if I don't replace it. ( Gary Moore, 07/13/2020 )
The differential pressure switch reacts to a loss of master cylinder hydraulic pressure in either side of the split hydraulic system and can illuminate a warning light at the instrument panel. When pressure is lost in either the primary or secondary circuit of the master cylinder, the switch closes. The electrical switch will remain closed until the malfunction is corrected. When both systems develop normal pressure, the switch will return to center and open the electrical switch circuit. A mechanically latched connector is attached to the switch. The switch has two tabs on a common terminal (positive) and is grounded through the master cylinder.

In most instances, you can continue operating the vehicle without this sensor being used but it won't alert you to a pressure issue in your master cylinder.