Community Forums

dpinvidic · 09-22-2014, 11:55 PM

I am having a problem with my newly installed AF1 brake system.
It now looks like something is wrong on the coach side.
I am not getting proportional control, it is full on or full off.
Here are some pictures of the pedal movement I took during testing.
I hooked up the air compressor to the air input connector on the TOAD.
Then I applied zero, 10, 15, & 20 lbs of pressure. the pedal moved in a little more with each additional increase in pressure. The last picture is when the air hose is disconnected and the breakaway switch is pulled.

Looks like the toad side is working fine, now I need to measure pressure coming from the coach at different pedal positions.

This might help someone in the future.
Regards,
Dan

Ray,IN · 09-23-2014, 08:26 AM

Great diagnostic work! I wonder if the installer tied-in to the compressor output side instead of the air-brake line?

waroland · 09-23-2014, 04:44 PM

I would guess that you are not tied to the metered air output of the brakes.

1mainiac · 09-23-2014, 05:08 PM

Plumbed wrong in coach. Get it to someone who knows what they are doing. Follow your air line from the back of the coach to the service valve or relay valve. Bendix 102626X R-12 Relay Valve with Vertical Del Ports, 4 PSI Crack Pressure, 1/2" NPT Del Ports: AnythingTruck.com, Truck & Trailer Parts and Accessories Warehouse

It should look something like that with a line coming from the air tank or supply that should be check valve protected. The service line should come from the brake pedal but likely comes from tying into the service side of your rear brakes which is where I would do it.

dpinvidic · 09-23-2014, 10:58 PM

Thanks for the comments. I exchanged some e-mails with SMI support, and sent them a picture of the lines where I made the connections. They confirmed the connections are correct.
My next step is to put a gauge on the actual metered air line going into the SMI coach air assemble (the SMI relay valve) and confirm that the coach is sending out a proportional pressure.
My understanding of these air relay valves is that they are supposed to mirror the control input pressure on their outputs.

My coach brakes "SEEM" to be working correctly. The metered air actually comes from the output of the service brake relay valve (not the treadle valve). So it is likely that one of two things are happening.
1. The output of the service relay valve is not linear...it jumps from 0 to around 20psi.
2. There is a problem with the relay valve in the SMI assembly...it might not be mirroring correctly.

[1maniac] - you are absolutely correct, and that is where SMI says to make the connection....the output of the service brake relay valve.

I won't get the coach home until 2 weeks from now...then I will take the measurements and post the results.
Hee is a video of the test.
. To make the video, I put a walkie-Talkie next to my phone so I could narrate the pedal pressure that was applied in the coach and if the dash light was on/off.

Dan