A/C Cooling Problem

Elvecinopoli · 4-12-10, 22:10

The car is an 1989 MX-6 LX . Non-Turbo with Automatic Transmission. The car does not belong to me, it belongs to a friend who has lent it to me as I am w/o a vehicle.It's A/C system has been inoperable for some years. I hope to repair his A/C as a thank you when I return it shortly. Though I have some experience working on cars (shade tree mec.)Any help is appreciated.

The car has been converted to 134a prior to this. My friend says the compressor would engage momentarily, it no longer did. I checked the schrader valves and they were loose. I tightened the schrader valves and vacuumed the system. It held -25 hg vacuum for 3 hrs before i disconnected the gauges.

I then opened the lines to the compressor and added about 6 oz.(read on a post it needs 8 oz and 2lbs freon)As some assurance I replaced the schrader valves and repeated the process with equal results.

After starting the car, turning the A/C on and fan to high(4) i added 12 oz of freon and the compressor engaged with slight cooling at the vents then it turned warm. The freon slowly entered the compressor as if it was full.I stopped the car and these are the readings on the gauges.

Readings as I charged the system
Low side: 10
High side: 88
I then turned off the car and these were the readings:
Low side: +95(pegged on gauge)
High side:95
I turned on the car and then the A/C and nothing happened.
I pushed the ECON button and the compressor engaged.These were the new readings:
Low side: -5(vacuum)
High side: 126
Through the sight glass some freon visible(able to see better as I added uv dye from can of freon) though bubbly. I was able to add another 12 oz can.

The thin line with sight glass was cool and the thick line was warm(both that lead from compressor to evaporator) Shouldn't it be the other way around?
Also the low and high side lines where the gauges are connected close to the condensor were very hot.

I suspect a blockage but not sure. maybe the expansion valve as the evaporator line temps are reversed?Also do these cars have orifice tubes and where are they located.

Also is the problem that the a/c button, econ button work intermittenly with the fan controls.(compressor would engage in 1 and 2 but not 3 and 4 sometimes just 1.) I suspected the resistors I had seen in another post but then after turning off/on the car and pushing the econ button the compressor would work on all 4 fan speeds. Very strange(ECU just popped into my thoughts)Don't know.

But first I would like any thoughts on verifying the blockage and where it might be. If I left any info out that may be useful let me know.

I Thank everyone in advance for taking a look. Thank You.

**fez626** · 4-13-10, 0:25

hey im not 100% about ac stuff but here is the shop manual chapter for the AC system. they have a bunch of trouble shooting info that might help you. also check out the FAQ for other chapters of the WSM. and also Keeloh did the Training Manual which is a sticky in the general forum.

and don't worry because its for the 90-92 b/c they are so similar, although take that with a grain of salt b/c it might be different. Good luck

http://manuals.wibla.net/mazda/90-92WSM/ChapterU.pdf

FF

**chief tool** · 4-13-10, 2:25

Yeah, it sound like a blockage to me....it could be a moisture blockage...if any moisture gets into the system it tends to freeze in the tx valve (which is not the ofrice type in these cars)

When it thaws it moves around the system until it re appears in the Tx valve again.

I would reclaim all the gas, change the receiver dryer and vac the system down for an hour and put the gas back in and see how you go.

it could still be dirt in the system......but its unlikely if the pipes have not been disconnected anywhere recently.

Elvecinopoli · 4-13-10, 9:15

Wow Thank You for the quick reply and thanks for the link. The scans will be indispensable. I have already printed them out. From the diagrams and from what i have seen physically, they appear identical. Again Thank You.

Elvecinopoli · 4-13-10, 9:18

Can't edit. The reply was to fez626.

Elvecinopoli · 4-13-10, 9:32

After further gauge readings I am sure the blockage is in the Txv thermostatic expansion valve(whether it is electrical or moisture or dirt is another matter). I believe the dryer is fine as the pressures equalize some what after sitting for a few moments. However since I am going to open it up after doing electrical diagnostics ,thanks to the scans from fez626, I am going to replace it(probably new o-rings too). The manual indicates moisture or dirt as you mentioned off the bat when an low side gauge indicates vacuum. Thank You as well for the quick response chief tool.

**SinCity** · 4-13-10, 12:09

Wait. The car was converted to R134a and now you are trying to fill it with R12? And you added 6 oz more oil to the system?

Elvecinopoli · 4-13-10, 12:42

Quote:

Originally Posted by SinCity

Wait. The car was converted to R134a and now you are trying to fill it with R12? And you added 6 oz more oil to the system?

No I am not trying to fill it with R-12. As per my friend when I asked to find out some info on the system, it was converted to R-134a about 8 years ago. it has not worked for the last 2years. I was using R-134a. I was able to add two 12ounce cans. 24 oz all together, short of the 32 oz specified.

After tightening the valves, I vacuumed the system for about an hour and 30 minutes. I let it stand with the gauges for 3 hours and the vacuum held at -25hg . I then decided to replace the valves as assurance and added 6 oz. of oil.(keep in mind that this was prior to reading a post that specifies 8 oz. of oil and 2 lbs. of freon) I figured 6 oz. more or less as there was oil in the lines of the reading gauges and vacuum pump outlet. I vacuumed the system again with equal vacuum results. Followed by the trouble I ran into.

However after reviewing the scans fez626 directed me to,and the cause of the symptoms that were spot on by chief tool, it appears i will have to open it up again. This time with the correct amounts specified.

Thank You for your reply and will appreciate any other input or advice.

**fez626** · 4-14-10, 12:25

Hey glad i could help

have you gotten to opening it up?

Elvecinopoli · 4-17-10, 17:08

Quote:

Originally Posted by fez626

Hey glad i could help

have you gotten to opening it up?

No not yet. I have been reading the scans for the third time. I intend to go through every electrical diagnostic step to make sure all sensors , switches, etc. work before opening it up. I intended to do it on my days off but now I have to unclog the sunroof drains as a priority as I got drenched a couple of times these past few days. Ironically I read a thread on here that covered that before it started raining and thought to myself , "that's good to know in case it happens". I'll report back when I find the A/C problem. Thanks again.