This summer I made a decision to get my dash AC working in my 1990 Regency. I looked at all our on line information and found that there was nothing which showed how the basic Acme system was wired in a Barth pusher chassis. This is the first thing which must be sorted out before getting to the mechanical issues. I completely traced the whole system in my coach, and a schematic will be made soon up which will be posted on Barthmobile.

For now, I thought I would post my findings verbally as they may be of interest to some of our members.

First, my coach is a 1990 Regency with Spartan chassis and 8.3 Cummins with front mounted rad. It has only front chassis AC - none in the rear as some of the coaches do. The front AC evaporator is an Acme unit with thermostat,expansion valve and high and low (separate) switches. The condenser is an ARA unit remotely mounted in the right rear fender well adjacent to the engine. My unit is heavily corroded and fans are seized. I estimate that the ARA unit had no more a rating than 15000-20000 BTU. The AC pump is a Seltec unit of 6 cubic inch displacement (too small) and appears to be in working order ie not seized. Screw clamps are used throughout and the existing hoses are not brittle but are rated for R12 only. My system is still closed -no open hoses.

The dash controls are Bi-level standard Acme which is the commonly seen unit used on Chrysler vehicles in the 1980s through 1993 with the last few years in the Dodge trucks only. My unit caught on fire this summer and I was lucky that the wire burnt off before flames could erupt. I purchased a new unit and installed it. Incidentally, all aftermarket suppliers of this switch have stopped supplying it at least here in Canada. I had to get mine off Ebay. They will be in short supply in the future. The current capacity of this switch is marginal when new and after corrosion builds up, they make a perfect resistor.

The AC harness for the Acme unit was factory made by Acme and supplied with the unit. It wires up the Chrysler control, the blower relay and the blower motor and its resistors. In the Barth application, it does not wire the low and high pressure switches. These are part of Barth,s wiring in the next paragraph. When you select AC on the control unit power is extended in three directions. First 12 volts is sent to the thermostat which is mounted on top of the Acme unit (outside). Second 12 volts is sent to a relay in the front wiring compartment which operates the vacuum pump( AC off- pump doesn't run). Third 12 volts is sent to the the blower motor via the blower switch and resistors. For low and medium speeds, the blower relay is not used and the resistors control speed with all current used passing through the Chrysler control. I estimate that this might be up to 8 amps or so at medium speed. When you select high speed, the blower relay kicks in and the blower gets is power direct from supposedly a 30 breaker source. I found that in my coach the latter feed was wired with 14 gauge wire (should be 10). I haven't validated the original breaker size but it should be 30 amp to match the 10 wire. I upgraded mine to the 30 amp and used a separate breaker.. Also found that the factory harness wired the power from the relay to the motor with 12 gauge and it was miles too long. Left the 12 gauge and took 2 feet out of the length to reduce voltage drop.

The above concludes all of the Acme wiring harness., The rest is Barth made. Picking up at the thermostat in the above paragraph, 12 volts goes from the thermostat to the front wiring compartment where it energizes two relays. The first I call the AC compressor relay and the second I call The AC condenser relay. Each of these relays sends 12v to the rear of the coach- the first one turns on the AC compressor and the second starts the condenser fans. The 12v relay output for the AC pump is routed in series with with the high-low pressure switches on the Acme evaporator. ie if the system pressure is too high or low, the signal will not get to the AC pump thus protecting the system. This is all done by routing wires all over the place on the term strips in the front wiring compartment. One thing Barth really bungled was the power to the condenser. In my coach, the condenser power (estimated at least at 10-12 amps) is supplied from the front compartment via the relay 35 feet to the rear using 14 gauge wire which is rated at 15 amps. There would be excessive voltage drop reducing the life and efficiency of the motors. Another relay should have been used at the back to supply power directly. This has now been added to my coach. Another incidental item to note is that Barth used type TEW fixture wire in my coach- all red in colour. This is high quality insulation wire rated for 105 degrees C- still in perfect condition in my machine.

This concludes my writeup- long winded but I hope this helps others. I suspect Barth used this arrangement in other pushers. I will do a separate report on the mechanical issues later.

Here is a good site for Acme AC parts. The person who runs this place worked for Acme for many years and has a lot of good information. Notice the links at the bottom of the page. One of them links to a book of schematics. It takes a while to decipher the book but once you do it has a lot of useful information also.

http://soldbyrichard.com/rvacheaterparts.php

Lance:

I am very familiar with this site. Purchased my replacement expansion valve and drier from them. Richard emailed me a copy of my schematic for the basic Acme system. I could not find any access to schematics on the actual site, I am sure Richard would have told me to get the information off the site, if available, instead of taking time to send me an email. Just checked again and cannot find any icons to take me to documents.

Thanks for your comments

Clint

Clint and Lance - Thank you for this posting!

This is very useful information. We have a 1994 Breakaway XL with the exact same dash HVAC. Ours actually works and blows both hot and cold - but - 90% of the output blows up through the defrost vents. It appears to be vacuum operated and stuck in that position due to no vacuum. It has a small vacuum accumulator inn the front, but I have yet to locate any vacuum pump/source. It is an 8.3 Cummins pusher with banks stinger and Allison 3060. Would love to get a copy of the HVAC schematic when you get it finished. Also any clues about what Barth did to generate vacuum on this coach would be much appreciated.

Thanks,
Richard & Penny Farr - Tulsa, OK
richardfarr@cox.net
918 645-1514

Rich:

I have been very busy as of late and haven't had a chance to make up a proper schematic that would be readable. Will get to it this week and post accordingly. On my coach, the vacuum pump is located in the right front fender well in front of the tire up on the front bumper superstructure. My unit is working and is controlled by the Chrysler AC dash control unit via a relay in the front wiring compartment ( as outlined in my write up). The vacuum output of the pump goes to a vacuum reservoir which is round and the size of a softball. It is located in the front behind the access door to the front mounted rad and above the top of the rad. It has an output hose which runs to the Chrysler control. My vacuum pump is quite audible when running. You should be able to hear yours if it is original. You could also go your reservoir and slip off the supply hose and see if you have a draw. If there is a draw, the problem is either a degraded vacuum line off the Chrysler control, the control itself or a bad vacuum motor on the evaporator. If you have vacuum to the control and the vacuum lines feel pliable, it most likely a vacuum motor. The motors will all have to be checked with a vacuum hand pump (typical unit made by Mityvac)

If you have done the above checks, you will find the problem. The vacuum motor is most likely at fault and will have to be replaced. Lots of information on our forums about a replacement.

You are lucky that your system still works. Keep it maintained as best you can.

Clint

Many Barths used a vacuum venturi generator like this one, they are NLA and most people as I have replaced this with an electric vacuum pump.

venturi vacuum generator

If you have a vacuum operated cruise control there are probably two of these, one in fron to poperate the vacuum control on the HVAC and one in the back to operate the cruise.

Thank everyone for the replies and good info. Our coach has a king electronic cruise control so the only place vacuum is required is for front HVAC. It is raining here, but as soon as get a nice warm day, plan to use your suggestions and track down the vacuum source. Guessing a small inop electric pump. Great suggestion to disconnect the hose from the softball size reservoir and trace it back.. This is our 4th coach and all in all it is the best we have ever owned. Got solid 10 MPG at average 55/60 MPH on recent trip to Texas. Always plenty of opportunities for 'improvements', but a man needs a project.. Changed all the relays and the DC power solenoid. which solved several intermittent electrical issues. Next project is to change clearance, marker and dash lights to LED. Will make the light switch a lot happier :-)..
Really appreciate this site..

Rich and Penny Farr
Tulsa, OK
1994 Barth Breakaway XL
8.3 Cummins with Banks Stinger
Allison 3060