New Holland and air brakes

[mushnt grummmble]

The trailer will release over about 4bar in the red line
Use the trailer suzy and coupling to test if theres any pressure on the tractor like i described above

 

[Mursal]

Well I didn't know that the release pressure was so low, thanks @mushnt grummmble

I was over complicating the thing using a pressure gauge .........

 

[Lincsman]

FFS the tractor isnt making a noise when the handbrake is taken off, trailer or no trailer... theres the fault then!

 

[cosmagedon]

That's all our T7s go up to so you have plenty of air. Plus they won't be spring brakes so you don't necessarily need the air to lift the brakes but that's complicating matters.

I will have a look through the drawings now and see what relays are used. You any good with electrics? You could check to see if your getting power at the solenoid, I think the handbrake one will be 12v when the handbrake is off.

 

[farmerman]

Just pull the yellow line
Then undo the yellow coupling off the trailer and plug it in and see if air comes out when the handbrake is down

We haven't done this but it dies pump up the trailer all ok and no problem just not releasing the brakes of the trailer

Well I didn't know that the release pressure was so low, thanks @mushnt grummmble

I was over complicating the thing using a pressure gauge .........

Sounds like you've learnt something new @Mursal at our expense hahah inleast you'll be a happy every day's a learning day

FFS the tractor isnt making a noise when the handbrake is taken off, trailer or no trailer... theres the fault then!

And yeah I think there's the fault to how to fix this fault though? Change sensor?

That's all our T7s go up to so you have plenty of air. Plus they won't be spring brakes so you don't necessarily need the air to lift the brakes but that's complicating matters.

I will have a look through the drawings now and see what relays are used. You any good with electrics? You could check to see if your getting power at the solenoid, I think the handbrake one will be 12v when the handbrake is off.

And that's interesting to know sounds like getting up to the rite pressure all ok

Yeah thanks very much for that it could be very useful and yeah not the best but can text with a voltmeter we tested the line to the solenoid that I uploaded picture to earlier and that had power to it fine but didn't check the other two for power on top of were air fittings are. But is the handbrake one the one rite next to handbrake lever?

 

[Chuckie]

We haven't done this but it dies pump up the trailer all ok and no problem just not releasing the brakes of the trailer

The red line pumps the trailer up, the yellow one operates the brakes. The yellow line should not have any pressure in unless the hand brake is on or the brake pedal is pressed. As @mushnt grummmble has said, you need to see if there is pressure all the time at the yellow coupling, if there is, that is your problem.

 

[Mursal]

Had a bit of a head scratch ...............
Would it not be better to just connect the Red line and see if the trailer brakes comes off first, before connecting the yellow?
Or am I still missing something?

 

[Tech-15]

Looking at the position of the trailer air brake relay us must be an early t7. 200 as they ended up fitting the relay the other way around to stop water ingress into the relay causing Ur problem. If u can work out which of the two solenoids is the one for the handbrake pull the plug off and put an earth and 12volts to the solenoid. If it then releases the air off the trailer than solenoid is ok. I'm still thinking it will b the relay. U could get one and try it if u have a nice local dealer who would have it back if it didn't cure it.

 

[farmerman]

Thabkyou for advice everyone!!

Had another play this morning quickly we plugged in the red line which therefor pumped the trailer suspension up and filled the air reservoir.

We then plunged the yellow brake line of course brakes were just locked. We then unplugged yellow brake line and it dumped trailer pressure and released the brakes.
We then proceeded to test the yellow brake line side and pushed in the yellow brake coupling on tractor side and was just pushing air out all the time with handbrake of and no footbrake so went over to the Fendt tractor and that was pushing no air out until handbrake was on or foot pedal down so therefor we think the tractor yellow brake side has an issue and just continuasly
Pumps the air which is causing brakes to lock and not release. Does anyone know next step to stop it pumping air continuasly?

If you fill the trailer up with air and the brakes are on pull the yellow line off with the handbrake off.the trailer should dump its brake pressure and release
The tractor will probably have pressure in the yellow coupling to see press the center with a dowl of some sort.
If things are correct then there should be no pressure in the tractor side with handbrake off and foot pedals up

Basically done this and found out the problem we hope so getting there slowly lol

 

[farmerman]

Are these the solenoid that could be faulty on top near the cab and back of air brake couplings?

 

[farmerman]

So this is what we done and what we left coupled in and took out and found out was still pumping air out

 

[e3120]

As a few(!) times above the tractor thinks the handbrake is still on and is pressurising the yellow line. The clue was the lack of hiss when the handbrake is released, trailer or no trailer. Post 48 suggests how to narrow down the cause to the relay/solenoid. If both these OK, then it could be the handbrake switch but you'd likely see other symptoms.

 

[Mursal]

Might I suggest in the absence of those that know .............................
If you disconnect the electrical connectors one at a time on the pictures above to see if you can control the air flow to the yellow line? Just don't mix the connectors up.
Then with the connectors back on, go to the relays and see can you remove one to give the same level on control over the air. Replace this relay.

 

[Chuckie]

So this is what we done and what we left coupled in and took out and found out was still pumping air out

Why is the yellow line on the trailer coupled to the red one on the tractor?

 

[Mursal]

Click here to double check

 

[Lincsman]

Why is the yellow line on the trailer coupled to the red one on the tractor?

I think its yellow pretending to be red, and the black with red ends is pretending to be yellow! Perhaps the OP might like to get 2 spanner's and put that right to start with!

Picture 2 showing the screwed on wire connector is where the issue is, its the yellow tape marker-ed one, ether wire or solenoid.

 

[dave7840]

Don't know if this is of any use. from t7000 manual, should be the same as on a t7. Edit fuse is no 16 its not that clear

 

[cosmagedon]

Just had a quick look through the schematics I've got, they're for a long wheel base T7 with sidewinder but I presume they would be the same? Check fuse F51 (25amps) F16 (20amps) first, if they are OK check relays K047 and K011 are clicking when you put the handbrake on and off. Let me know how you get on.

 

[farmerman]

Sorry yes I've realised the pipes are back to front but not been used to air brake systemsfor long but Will rectify tomorrow

it all seems to be pointing to a handbrake circuit fault.
I'll check the fuses And relays in the fuse box tomorrow. Any other areas I should be checking ?? and areas I can run tests on to rule them out ? But think there's enough to be checking for now lol Could that relay under the cab on the photo also becauseing the problem? On The trailers brake relay assembly

Thank you all for uploading your diagrams and general help much appreciated .The tractor is a short wheelbase with sidewinder so should be identical for the wiring and other peoples diagrams too will have a good look tomoz at all
That everyone has said and let you know if we get any further.

 

[8100]

Will the handbrake plunger/detent switch be electric now? It must be stuck either way on the handbrake on off circuit.