[marcel27208]

OK heres some background info.... i was DOT'ed in VA about 6months ago, i was shut down because DOT said i had a bad tractor protection valve, he had me push both brakes in with red airline unhooked and let air leak out, and the buttons were suppose to pop out, only the trailer brake did, so i had TA come out and give me new tractor protection valve and i was on my way............. i havent been DOT'ed since but the other day i went to test it and it still didnt work.(only trailer would pop out) I bought a rebuilt MV-3( i think thats what it is) and replaced the tractor valve and the seal... Now they both pop out, but when i press just the tractor brakes button pump down air, the button still doesnt pop out(although the buzzer does come on) my question is, is it suppose to???? and any suggestions on how to fix?

[bob h]

Originally Posted by marcel27208

OK heres some background info.... i was DOT'ed in VA about 6months ago, i was shut down because DOT said i had a bad tractor protection valve, he had me push both brakes in with red airline unhooked and let air leak out, and the buttons were suppose to pop out, only the trailer brake did, so i had TA come out and give me new tractor protection valve and i was on my way............. i havent been DOT'ed since but the other day i went to test it and it still didnt work.(only trailer would pop out) I bought a rebuilt MV-3( i think thats what it is) and replaced the tractor valve and the seal... Now they both pop out, but when i press just the tractor brakes button pump down air, the button still doesnt pop out(although the buzzer does come on) my question is, is it suppose to???? and any suggestions on how to fix?

there is no logic behind both buttons popping at the same time =(

i have been unable to find any evidence in the 121 that indicates that the yellow button must pop out. the red button must pop between 20 and 45 psi, although it seems as though exceptions do exist

[One]

Im under the impression that the yellow button is supposed to pop out, but ive only checked once or twice and found the yellow one to pop almost at 0 pressure. Maybe this helps.

[marcel27208]

you see thats the thing, a few people say yes it has to pop out and others say only the red has to pop out.............. NC scales were working VERY hard today and was gonna ask but didnt want to go through a DOT...!!!

[naterosy]

The whole point of the Tractor Protection Valve is to protect the air in the tractor in the event of a trailer breakaway.

Hence the only button to come out would be the red trailer supply valve. You would want to apply the parking brakes while your driving on the tractor. Now the PP1 yellow valve should pop out when the air gets low because they want you to be able to stop..

Before the air drops to that point though, the trailer supply valve would pop out and close and the air would be saved. (Normal operation for truck service brakes) ------ So if what your saying is true, then it is now working normally.

[yoopr]

I never had a DOT inspection where they take off the airline itself. Normally they have you pump the brakes to see when all the bells and whistles start yelping and at what PSI

[marcel27208]

Originally Posted by yoopr

I never had a DOT inspection where they take off the airline itself. Normally they have you pump the brakes to see when all the bells and whistles start yelping and at what PSI

Well thats what everyone else tells me they never had A dot like that, but i guess thats just another way of letting the air get down,

And NATEROSY, yes both do pop out at the same time when hooked to a trailer BUT, when i just press in yellow and pump down, it doesnt pop out, I looked at DOT reg book and it doesnt actually give the specifics about what needs to happen actually, so im still confused???????? :shock: :shock: :shock: :shock:

[bob h]

quote="naterosy"]The whole point of the Tractor Protection Valve is to protect the air in the tractor in the event of a trailer breakaway.

the tractor protection valve is not part of the dash valve/module, it is a separate valve usually mounted near the rear of the tractor cab

the TPV will shut off air supply to the trailer irregardless of what the dash valves are doing... i.e. - the red dash valve can be pushed in, and the trailer spring brakes could be applied because the tpv has blocked trailer supply air... the point being; the 2 operate independantly of each other

Hence the only button to come out would be the red trailer supply valve. You would want to apply the parking brakes while your driving on the tractor. Now the PP1 yellow valve should pop out when the air gets low because they want you to be able to stop..

you will be stopped by the springs (overcoming air pressure) long before the yellow button ever pops

Before the air drops to that point though, the trailer supply valve would pop out and close and the air would be saved. (Normal operation for truck service brakes) ------ So if what your saying is true, then it is now working normally.[/quote]

[bob h]

Originally Posted by marcel27208

Well thats what everyone else tells me they never had A dot like that, but i guess thats just another way of letting the air get down,

And NATEROSY, yes both do pop out at the same time when hooked to a trailer BUT, when i just press in yellow and pump down, it doesnt pop out, I looked at DOT reg book and it doesnt actually give the specifics about what needs to happen actually, so im still confused???????? :shock: :shock: :shock: :shock:

if you can tell me exactly what valve you have, i can certainly tell you what it should do

line set ticket, or dealer can find it with the vin #

[marcel27208]

OK i got it straight now...... yeah i know that Tractor protection valve is located at rear and that was what i had replaced ............... but here is the deal......... during a DOT inspection they can check your TPV a few different ways, one way is push BOTH buttons in and pump brakes(or is u have a trailer unhook red airline) until between 20-45 psi they BOTH should pop out..... another is just press in YELLOW and pump down and it should pop out before 0psi.... now my thinking was if i press in just the YELLOW that it should pop out between 20-45psi. But its actually suppose to pop out b4 0psi, which in testing today it did.!!!!! YES im DOT legal :lol: i replaced the valve itself(that u push in) behind the dash(had to take dash board off), IM GOOD TO GO!!!!!!!!!!!!!!!!!!!!!! thanks guys for all your help!