Re charging dash AC

Topic: Re charging dash AC (Read 2022 times) previous topic - next topic

Re charging dash AC

January 19, 2017, 06:24:43 pm

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.

Re: Re charging dash AC

Reply #1 – January 19, 2017, 07:52:17 pm

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?

Re: Re charging dash AC

Reply #2 – January 19, 2017, 07:56:30 pm

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.

Re: Re charging dash AC

Reply #3 – January 19, 2017, 07:58:05 pm

Also to your question no change in pressure on guage.

Re: Re charging dash AC

Reply #4 – January 19, 2017, 07:59:35 pm

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.

Re: Re charging dash AC

Reply #5 – January 19, 2017, 08:00:53 pm

Warming the can always helps.

Re: Re charging dash AC

Reply #6 – January 19, 2017, 08:05:34 pm

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.

Re: Re charging dash AC

Reply #7 – January 19, 2017, 08:07:12 pm

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.

Re: Re charging dash AC

Reply #8 – January 19, 2017, 08:25:06 pm

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.

Re: Re charging dash AC

Reply #9 – January 19, 2017, 08:38:36 pm

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.

Re: Re charging dash AC

Reply #10 – January 19, 2017, 10:25:33 pm

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.

Re: Re charging dash AC

Reply #11 – January 19, 2017, 11:02:25 pm

It takes several pounds to fill the system.

Re: Re charging dash AC

Reply #12 – January 20, 2017, 12:40:38 am

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

Re: Re charging dash AC

Reply #13 – January 20, 2017, 07:02:55 am

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

Re: Re charging dash AC

Reply #14 – January 20, 2017, 08:10:25 am

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.

Re: Re charging dash AC

Reply #15 – January 20, 2017, 08:15:20 am

What should the pressures be at 70 F for our A/C systems when full? Jim

2002 U320

Re: Re charging dash AC

Reply #16 – January 20, 2017, 09:06:00 am

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.

Re: Re charging dash AC

Reply #17 – January 20, 2017, 09:11:26 am

Quote from: Jim Frerichs – January 20, 2017, 08:15:20 am

What should the pressures be at 70 F for our A/C systems when full? Jim

2002 U320

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

Re: Re charging dash AC

Reply #18 – January 20, 2017, 09:31:28 am

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 .

Re: Re charging dash AC

Reply #19 – January 20, 2017, 10:01:27 am

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.

Re: Re charging dash AC

Reply #20 – January 20, 2017, 10:19:42 am

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.

Re: Re charging dash AC

Reply #21 – January 20, 2017, 02:21:42 pm

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.

Re: Re charging dash AC

Reply #22 – January 20, 2017, 02:34:15 pm

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.

Re: Re charging dash AC

Reply #23 – January 20, 2017, 02:40:31 pm

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.

Re: Re charging dash AC

Reply #24 – January 20, 2017, 03:25:00 pm

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

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