Brake pressure differential switch leaking

My sons 72 leaks from the inside of the plastic switch on the proportioning valve. Does the plastic screw in switch hold back the brake pressure or is it the o-rings inside the proportioning valve that seals it?

We found the switch leaking after rebuilding the proportioning valve and replaced it. Now, the new switch is leaking again.

Could it be that the fittings are not tight enough. Had that happen before. Have to be really tight.

Well, it’s leaking thru the switch and out where the electrical contacts are… not sure how tighter would help? I can wipe dry, the base touching the valve is dry, but the contacts are wet.

(Yes, its frustrating me!)

The o-rings inside the proportioning valve provide the seal.

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The new reproductions are known for leaking there.

Crappy Product Link

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Thanks Mike. I was afraid of that.

Thanks for the Link, Royce!