My dash ac compressor was replaced about three years ago along with new ac lines filter dryer etc. Over time freon as leaked out where I now need to add. I purchased some freon 134a in a can with a gage. I turned on AC and followed instructions. The compressor clutch is not engaged because freon level is to low. Now this is where I need some help. How do I get the system to draw in the freon on the low pressure side. The compressor has one red wire connection. I assume the case is grounded. Can I jumper the compressor by disconnecting the red wire and bring a seperate 12v to it. And will the compressor running will this pull in the freon. Suggestions please. the gage reads about 100 on the supplied gage.
The can will provide enough pressure to clos the low pressure switch. It might take a little time and more than 1 can. When you hooked it up and opened the valve did the can pressure drop?
craneman, The low pressure connection is at the front of my coach and I cant get the gas to travel. Would putting the can in warm water help.
Also to your question no change in pressure on guage.
I won't guarantee that it is OK on yours, but I have "hot wired" many compressors over the years to get the freon in and it always seemed to work fine.
Warming the can always helps.
Dave looking at the compressor there is only one red wire which I assume is 12v. Would it be wise to start by warming the can before jumping the compressor.
If the can pressure didn't drop the Schroeder valve might not be getting depressed. The collar has to be pushed down and locked on the hose and usually opens the valve. Also the can has to be punctured with the valve on the can. Warm the can as suggested and if the pressure still doesn't drop jump the compressor.
Craneman that sounds good will try this weekend. I'll bring a 12v wire right from the battery to the compressor if I have to jumper. I might buy a can of AC Pro . Its more expensive than the one I have but it may have a better connector. I'll keep you informed. Thanks Craneman and Dave.
My compressor is running with the low side at 15 lbs. and the thermostat shuts it off when the dash register gets down to 40 deg. That is why the can should provide the needed pressure. Does the gauge read pressure when the valve on the can is closed? If so what is it.
I've never tried to warm the can first but worth a try. Warming it while the freon is going in speeds things up. The can will get VERY cold.
It takes several pounds to fill the system.
I think the capacity of my system is over 10 lbs. I'm not home and can't look it up but check your owner's manual.
I had to replace my compressor clutch. Then I took my coach to the local goodyear service center and they did a normal AC service for just over $100. Took them about an hour and two cans of coolant to top off the system. It did take a little convincing that the coach system was just like a cars only bigger. They had a much more reasonable labor rate than any of the coach service places and were very close to home.
Hope this helps,
Rich
First off If you are going to work on your A/C you need a proper set of gages.
Readthrough this
Troubleshooting with Gauges FAQ (http://aircondition.com/tech/questions/82/Troubleshooting-with-Gauges-FAQ)
Craneman the reading on the el cheapo gage is around 95. Trying to reduce number as stated earlier but dont seem to have enough pressure to push gas. Thats why I will try another brand of can freon warm it in water and maybe jumper compressor to engage clutch. When I release valve pressure on guage does not change.
What should the pressures be at 70 F for our A/C systems when full? Jim
2002 U320
First off just because the compressor won't come on does not necessarily mean you are low on refrigerant. The low pressure cutoff shuts the compressor off at about 20 psi. If you are showing above that on your gage the compressor should come on if only for a instant until it pulls down below 20 psi and shuts back off. You really need to have someone else turn on the A/C while you are under the back looking at the compressor to see if it tries to engage. Check fuse or circuit breaker and even the relay if it has one.
At an ambient temp of 70 degrees with the system off. not running pressure should be 70 or 71 psi for 134a refrigerant.
With refrigerant pressure changes with temperature.
Here is a temp pressure chart for 134a
Pressure - Temperature Chart for HFC-134a (http://www.pacificseabreeze.com/tech-library/heat-and-insulation/R134a-PT-Chart.htm)
Stump, I believe it has a 15amp fuse, but I havent found it . Its not in the fuse panel . It must be inline somewhere. Nothing up front however I will look in the area behind guages .
There is usually a high pressure cutoff switch also and it could be a combined switch that runs the condenser fans and controls the compressor cutoff This is usually located on or near the condenser itself. It will be in the liquid line from the condenser to the expansion valve,could be in the accumulator/reciever dryer itself. It would have 4 wires if it controls fan and compressor.
The different years and models change the A/C set-up. On mine the high pressure cutoff is on the drier-filter at the condenser. With what you are reading on the gauge the low pressure cutoff is not stopping the compressor just as Stump stated. you can jump the compressor with the pressure you are reading just to get the charge correct, but you still have another issue stopping the compressor.
On my 96 U320, there was a bimetal type 15 amp fuse on the sheet metal behind the driver rear tires. It was corroded so it did not pass power through to the compressor clutch. This type of fuse is very common, inside a small can with two small bolts for electric wires.
The dash air in my 96 U320 quit working a couple years after I recharged it using four or five 1 pound cans of 134a. I had to fix the fuse I spoke about in my previous post before the recharging could be done. When it quit the second time, it would not take 134a, even though I could see the compressor clutch was engaged and the compressor was spinning. The problem was that the compressor had quit compressing and had to be replaced. Determining a problem with the compressor requires a set of two gauges (a low pressure and a high pressure) and some knowledge. I bought the new compressor on eBay but had it installed at an shop in California.
Note that 134a works at higher pressure than R12, puts higher loads on your A/C system, and often causes failures after converting from R12. Also 134a will not provide as much cool air as R12. There are other better refrigerants available today.
One more thought.
Are you sure the clutch is not engaging because the pressure is low?
My clutch was bad. I did a post on changing it out.
Rich
Well I could have taken my coach in and had it repaired as someone has suggested. But I'm one of these guys that knows nothing and asks for help. Well ok I know a little. Anyway I think Wyatt has hit on something. First I checked voltage at compressor and there is none. I then checked voltage at sw. on the accumulator and there is none. And I did find the fuse Wyatt is talking about and mine is very rusty also. After the fuse it feeds a relay that feeds the AC compressor and thermo dash ac. My fuse is hanging by its wires. I will get my fat self under the coach and change out fuse. then we will see what happens. You are never to old to learn and I am learning alot from all of you.
Checking the clutch is very easy:
With engine OFF, disconnect the wire going to the clutch (there is only one).
To the A/C clutch side, apply 12 VDC positive from any source (the remote start switch is an easy place to use as a source).
You should hear and see the clutch pull in.
This also works (only use temporarily) if you think your low pressure switch is preventing you from adding Freon/134A.
Thanks Brett, but I think based on Wyatt's post I'm hoping it will allow me to add freon after I replace the fuse. I will check the fuse before replacing but based on its condition its probably shot. If fuse proves to be good I will then put a 12v source to the compressor clutch. I will report progress.
Source for the fuse?
FYI,you can get a 30lb can of r134 from amazon for $120,will last a lifetime,but you will need
Gauges,those small cans add up quick.Plus you can use it for your car.
You can get a 30lb tank of R134A at Rural King for $99.99 if you have one near you.
R134a Refrigerant 30 LB Cylinder 6330 by Technical Chemical for .99 in... (http://www.ruralking.com/r134-r134a-refrigerant-30-lb-cylinder-6330.html)
Also;
Auto A/C Manifold Gauge and Hose Set, R12 R22 R502 R134A - Walmart.com (http://www.walmart.com/ip/163545704?wmlspartner=wmtlabs&adid=22222222222055892569&wmlspartner=wmtlabs&wl0=e&wl1=o&wl2=c&wl3=10372864484&wl4=kwd-1105717116914&wl12=163545704_10000000420&wl14=harbor%20freight%20ac%20gauges&veh=sem)
Well here is my update. Replaced 15 circuit breaker that Wyatt spoke about and then jumpered out compressor as Brett suggested. Freon flowed freely and put in about 22ounces of freon . With compressor jumpered out the discharge air is ice cold but as soon as I pulled jumper off, the compressor disengaged. There is no voltage at the compressor. I don't know where the low pressure sw is. It appears that as someone earlier said this may not be a freon or leak issue. By the way I purchased the 15 amp breaker at a local Car Quest. Where should I go next?
What was your pressure with the compressor jumpered ? This is an electrical issue you will have to follow from the a/c switch to the compressor on the schematic for your coach. There is a relay, the a/c switch and high and low pressure switches to check out.
Craneman the pressure was 25 with compressor running. The circuit breaker gets its feed from a solenoid. Then it feeds a AC comp. relay. One side goes to ground. One side goes to AC compressor and one side goes thermo dash ac. Don't know where high and low pressures swiches are dwg. doesn't show. High and low fill ports are at the front of the coach behind passenger side head lights. There are numerous relays at the rear of the coach I will have to find the right relay. Its a wiring nightmare.
Howdy joeszeidel,
Since you think it may be an electrical problem, maybe this print will offer some help. The date on print is 1995, so hopefully, applies to your coach. Note: there is three pages to this .pdf.
Good Luck, Dave A
Dave Thank you for that PDF. I believe I know where those high and low sw. connections are. The fact that one is red and one is black will help. My checking will go on later this week. Bad weather is headed our way. These drawing will make sorting the wiring a little easier.
You can jumper the switches one at a time to check them or buy a tool which I have three of, one for my crane and one for the motorhome and one in my shop. This tool will save a lot of trouble shooting time. It lets you apply power or ground to whatever you are checking. This comes with a 20 extension cable which I use in the motorhome to make it easier.
Power Probe 319FTC-RED Test Light and Voltmeter - Walmart.com (http://www.walmart.com/ip/Power-Probe-319FTC-RED-Power-Probe-III-Test-Light-and-Voltmeter-Red/29937543?wmlspartner=wlpa&selectedSellerId=550&adid=22222222227019767589&wl0=&wl1=g&wl2=c&wl3=75569392114&wl4=aud-273067696302:pla-175622185954&wl5=1014273&wl6=&wl7=&wl8=&wl9=pla&wl10=112354493&wl11=online&wl12=29937543&wl13=&veh=sem)
Craneman with the dwgs I got from Dave I think I know where the high and low pressure sw's are and I have a very good volt meter. With the engine running and the ac switch on. I could check for voltage at each of these switches. If there is voltage then switch is bad. If no voltage the I have to find source. Am I correct?
You have to check that the power passes through the switches. Start at the A/C power switch and go from there. I am assuming your coach has a separate A/C switch for the compressor that starts the condenser fan and the compressor clutch. That is how my '99 is wired. You don't need to run the engine to do these checks, just ignition switch on.
Yes I have a seperate ac sw. on my dash which is easy to get to. Never thought that, that sw. could be bad.
Check your temperature switch that is mounted to the outside of the evaporator box. It has a capillary tube that inserts into the evap coil.
check for voltage there and if present only on one side then temporarily jump it out. With a set of gauges hooked up you will see pressure drop on the low side and increase on the high side almost immediately, no need to run to the back of the coach for visual.
Contacts were bad in mine and got a new one from Napa.
Dave the high and low pressure switches are not behind my compressor. I have a cat maybe thats why. The wire leading to the compressor is numbered 6310 but I dont have a diagram. Craneman I checked front sw and it has power I even jumpered out but no change. Weather is declining will continue later this week. Getting to the evaporator will be a pain. Oh well its beer and football later whats wrong with that.
Looking at Dave's schematic, make sure you have power coming out of both relays.
Went to the coach today and discovered I have 4 relays at the rear on the drivers side. Also found a red wire broken off of one of the relays. Replaced the plug but not the relay. Hooked back up but still no compressor running. There is 12v at both the pins marked 86 and 87. Will purchase a relay and start swaping them out. The relay I rewired may not be for the compressor. I don't know why I would have four relays.
Howdy joeszeidel,
Not sure about 4 relays, but this attached electrical print, shows 2 relays associated with a/c system. See the dashed line outline near the bottom center of print. The devices (relays, isolator, solenoids, self-resetting 12vdc breakers, etc,) on this panel is located under the bed, in the front of the engine compartment, on driver's side. The print date is 1992, so hopefully, close to what your system may be.
Good luck, Dave A
Hi Dave I will certainly check under the bed. I really have 4 relays all seem to be the same all mounted in about a 4 inch square area. I plan to buy a standard 5 blade bosch relay and start checking each one to see if I can get power to the compressor. thanks for your help
Well I am in a funk. I said yesterday I had 4 relays. Turns out only 3. Dave none under the bed, they are all bunched together. Today I bought a relay and started switching them out to see if that would help. No help. I checked voltage at low pressure sw. on dryer and jumpered out the sw. Still no compressor. The condenser fan does run. The two 15amp breakers are fine. Don't know where to go next. Maybe the repair shop.
Howdy joeszeidel,
If you're thinking of having a tech look at the problem, one of the very best is in the area. Might be worth a call.
Paul Yasbeck
(Foretravel Savvy with multiple recommendations)
813 382 0869
120 Ice Cream Rd.
Leesburg, FL
Good luck, Dave A
Thanks Dave, I know Paul have worked with him before.
Check back in if you get it solved, good information for possible future problems.
Joe you've fought the good battle. It may be time for the repair shop. Try to pick one where they will let you watch and educate you while doing the repair. The knowledge will serve you well down the road.
see ya
ken
Did you check to see if the thermostat in the evaporator is calling for the compressor to run?
Well Ken you may be right. But I'm a stubborn Hungarian who doesn't quit. Before I do quit I have to check the sw at the evaporator. My question is can I see by pulling the panel off at the passenger seat and lifting the dash or do I also have to remove the center piece as well. Can someone give a good location. I will try a jumper out to see if that works. I cant quit when everyone has taken time to try and help me.
I look forward to seeing what resolves the problem. I have had Cummins shop, MOT, Bern'd, and FT all try their hand at fixing the A/C with no success. Replaced the compressor and dryer Bern'd, replaced the condenser at FT. still not working. Like to know of anyone that can fix it instead of throwing parts on my dime.
Trying to figure out ,are we talking about Zeidels ac or John/pats?If John/pats start from problem and explain, we love to help but
need info.
I have been following this and it about joeszeidel's problem. No power to compressor.
John did not say specifically what his problem is just that the air doesn't work.
Well folks I tried to locate the temp. sw outside the evaporator. And I am not having any luck. I can lift the top section of dash and remove the panel to the right of the evaporator but can't figure out how to remove the front. But looking down fro the top I dont see anything like a sw. with two wires to it. Am I on the right track?
Joe, on our 1999 U270, I believe I saw the evaporator switch on the left side of the Airbox. I could be wrong, because I wasn't looking for it while I was doing the heater core and the floor in our coach. You might try removing the panel in front of the gas and brake pedal's and turning into a pretzel to have a look.
Don
Thanks Don, I have removed duct fro airbox on that side and will try and remove that panel. Actually I can get down there pretty easy for a 70 year old.
We have a U280 GV so I cant advise you where the T-Stat is located in a U320 coach, but both are a 95 model so I would think the switches are very similar or the same. I have attached a photo of mine of the back side after removal.
Hope it helps,
Thanks now I know what I'm looking for. Now I just have to remove the front panel infront of the evaporator box. This thing is really on there.
I thought I would update everyone on my AC issue. With the help of a forum member I have been making some progress. I was able to find a dwg. that better showed how its wired. First I verified that I had 12v coming into and out of the ac switch on the dash. Then I went the rear of the coach and unplugged the compressor. I connected a wire to the compressor source wire and then ran a continuity check to the plug wire going to the relay. I found that the wire was on the relay that was supposed to go to the condensor. I also verified that I had voltage on both sides of the binary sw on the drier. One wire from the binary sw. feeds the relay for the compressor. I now have three out of four wires identified. One wire to the compressor, one to ground, and one from the binary sw. The last wire should be coming from a 20amp. breaker that I have not found and it should be carrying 12v. I have found two 15amp breakers which are hot. Once I find the 20amp breaker and get 12volts. I then believe the relay will kick in and my compressor will start . John/Pat I hope this helps.
Do you have the 20 amp breaker on the panel under bed as we do?
johnH
John there is nothing under the bed. Its interesting to note, that one of my drawings shows two 15 amp breakers and another dwg. shows two 15amp breakers plus a 20 amp breaker . What ever the case I will trace wire from relay back to a breaker somewhere. Since my coach is such an early build who knows what I'll find. I believe everything is right there behind left rear tire its just that its very dirty and with primus everything is jambed in.
What is the build number of your coach? Mine is 4726. I wonder how close they are.
David build number 4558 April 94
OK Joe then it may be on the board behind tire. It will be one of those little metal elongated with 2 studs and is carried in most parts stores.
JohnH
John, is the relay you are mentioning under the bed on or near the isolator panel?
Don
my is there.
JohnH
Interesting! I wonder if it was one of the very first U320 models. Ours was built in February 1995.
John relays, solenoids and breakers are all bunched together. I just need to sort it out. David according to Foretravel I have the first unicoach sold
That's neat! You own a piece of History!
Well I am happy to report my compressor is running and the ac is blowing cold. The 20amp breaker I was searching for was hidden behind the relay I was working on The relay was actually attached to one of the breaker studs. I removed and replaced the breaker, and reconnected the wires and compressor is running fine. Thanks to all who helped me through the process and special thanks to Stump who helped behind the scenes. You dont need to know alot about AC but a little DC knowledge helps and a wiring diagram is a must.
Where in the coach are that particular breaker and relay located?
I'm glad you found it!! My pleasure helping you out. ^.^d
David on my coach all the relays and breakers are located on the drivers rear behind the rear wheel well. If yours is like mine the breakers are little rusty rectangles with two studs on them. The relays are black and should clustered close to each other.