Pacbrake

Pretty much everything on the bottom side of the coach: Steering, wheels, tires, brakes, suspension
oldcobia
Posts: 109
Joined: Thu Jan 27, 2022 7:56 am
Location: N. Florida

Pacbrake

Post by oldcobia »

Pacbrake system already installed on my 95 Safari. Not working now. I understand that compressor should come on when ignition is turned on and foot pedal is used to activate system. I have 12v to one side of pressure switch when key is turned on but compressor doesn’t come on. Suspect pressure switch but test good according to their website. I can turn compressor on by jumping wires but that’s it. Any help would be appreciated. Compressor only runs brake system and air horn. Thanks
1995 Safari Sahara 35’ 5.9 Cummins MD3060
05wingrider
Posts: 104
Joined: Sun Oct 27, 2019 7:26 pm
Location: Spokane, Washington

Re: Pacbrake

Post by 05wingrider »

Oldcobia,
If you can activate the compressor by jumpering around the pressure switch, you've answered your own question - regardless what the site may say. Pressure switches do fail! To test your pacbrake, put a piece of tape onto the cylinder (since the only way to test them is either direct air to the cylinder or activate the system while driving - you can't test it otherwise).
Duane
96 Sahara 30', 250hp Cat 3126
Allison 6spd MD-3060
2015 Jeep Cherokee Trailhawk "Toad"
Spokane WA
oldcobia
Posts: 109
Joined: Thu Jan 27, 2022 7:56 am
Location: N. Florida

Re: Pacbrake

Post by oldcobia »

I’m guessing you mean by putting tape on cylinder it will be pulled lose if it had been activated. When replacing pressure switch do you recommend a pacbrake switch or another after market one with same pressure activation requirements. Pacbrake switch is very expensive but will use if needed. Thanks
1995 Safari Sahara 35’ 5.9 Cummins MD3060
05wingrider
Posts: 104
Joined: Sun Oct 27, 2019 7:26 pm
Location: Spokane, Washington

Re: Pacbrake

Post by 05wingrider »

I believe that as long as you find a pressure switch with the same cut off settings, you should be fine (and the same thread pitch, of course). One other thing to check for the operation of your system is the Humphrey Valve, also referred to as a Super Quick Exhaust valve (SQE) and make sure that the rubber diaphragm is intact and hasn't had anything like oil sprayed on it (chemicals will mess up the rubber and it will stop working). If you see problems with that valve, replace it! I found a place online (Cleanersupply.com) that has the valve for $16.45 (their part # PRT440).

I operated under the assumption that my pacbrake was working on my 96 only to discover that the diaphragm in mine looked like a rolled up chunk of gum (and it felt about like it, too). Used my compressor to test the air cylinder after lubing it and everything worked, just the valve was bad. Got a new valve and put it on, then took RV out for a test drive and the change was noticed almost immediately when I tried using it, thus my suggestion to double check the condition of that valve system. Its a super simple valve - an o-ring and a rubber diaphragm, and a repair kit is almost as much as just buying a totally new valve.
Duane
96 Sahara 30', 250hp Cat 3126
Allison 6spd MD-3060
2015 Jeep Cherokee Trailhawk "Toad"
Spokane WA
oldcobia
Posts: 109
Joined: Thu Jan 27, 2022 7:56 am
Location: N. Florida

Re: Pacbrake

Post by oldcobia »

Thanks again for your info.
1995 Safari Sahara 35’ 5.9 Cummins MD3060
stuplich@ymail.com
Posts: 1146
Joined: Mon Oct 28, 2019 8:51 am

Re: Pacbrake

Post by stuplich@ymail.com »

05wingrider wrote: Mon Feb 07, 2022 10:24 pm Oldcobia,
If you can activate the compressor by jumpering around the pressure switch, you've answered your own question - regardless what the site may say. Pressure switches do fail! To test your pacbrake, put a piece of tape onto the cylinder (since the only way to test them is either direct air to the cylinder or activate the system while driving - you can't test it otherwise).

Duane (05wingrider)
When/if the Pacbrake air is pumped up the Pacbrake operation can be tested without the engine running, or the coach moving, by momentarily applying a 12V jumper to pin #86 of the Pacbrake cube relay.... (which on my coach is the center relay in a row of 3 relays located on, mounted to, the inside of the bed foot board)....

BTW, on my coach the left, street side, relay is for the 12V Pacbrake air compressor and the right, curb side, relay controls the auto retract function of the Kwikee steps.

Image
CUBE RELAY
Image
CUBE RELAY WIRING DIAGRAM
Mel
'96 Sahara 3530, mine since '01
250 hp 3126 Cat, MD3060 Allison
wolfe10
Posts: 222
Joined: Sun Oct 27, 2019 4:12 pm

Re: Pacbrake

Post by wolfe10 »

OK this post concerns a 1997 Sahara, so yours MAY be different.

The OE set up was "not the best".

Our compressor (terrible location over the rear axle) was frozen up.

New compressor to protected area in driver's side rear compartment.

And totally rewired so the pressure switch was only the "trigger" to close a relay (rather than all the power to run the pump going through the switch.

Not a difficult "rework".
Brett and Dianne Wolfe
Ex: 2003 Alpine 38'. Ex 1997 Safari Sahara. Ex 1993 Foretravel U240
Moderator, FMCA Forums 2009-2020
Chairman, FMCA Technical Advisory Committee 2011- 2020
Moderator, http://www.dieselrvclub.org/ (FMCA chapter) 2002-
1Lotosrggp
Posts: 51
Joined: Sun Oct 27, 2019 6:08 pm

Re: Pacbrake

Post by 1Lotosrggp »

Here is the pacbrake updated wiring diagram.
PacBrake wiring update 177.pdf
(123.89 KiB) Downloaded 216 times
Tom
97 Sahara 3550
3126 CAT 300hp
oldcobia
Posts: 109
Joined: Thu Jan 27, 2022 7:56 am
Location: N. Florida

Re: Pacbrake

Post by oldcobia »

Thanks for all the input. Will try to track down issue and repair this weekend. Work keeps getting in the way. Also found my vacuum pump is a Gast pump located behind right rear wheel. Terrible location. Sending it for repair if possible.
1995 Safari Sahara 35’ 5.9 Cummins MD3060
wolfe10
Posts: 222
Joined: Sun Oct 27, 2019 4:12 pm

Re: Pacbrake

Post by wolfe10 »

oldcobia wrote: Wed Feb 09, 2022 8:31 am Thanks for all the input. Will try to track down issue and repair this weekend. Work keeps getting in the way. Also found my vacuum pump is a Gast pump located behind right rear wheel. Terrible location. Sending it for repair if possible.
Verify this is a vacuum pump-- suspect it is used in that application as a PRESSURE pump.

And, at least on the 1997 Sahara, I was able to relocate the pump to the driver's side rear bay-- out of harms way. Added a 12 VDC muffin fan that ran of the same relay as the pump to cool the pump head. Relay used, so pressure switch only closes the relay with larger gauge wire (fused) to run the pump-- far less voltage drop and not hardtiming the points in the pressure switch with high-amp loads.
Brett and Dianne Wolfe
Ex: 2003 Alpine 38'. Ex 1997 Safari Sahara. Ex 1993 Foretravel U240
Moderator, FMCA Forums 2009-2020
Chairman, FMCA Technical Advisory Committee 2011- 2020
Moderator, http://www.dieselrvclub.org/ (FMCA chapter) 2002-
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