Air Conditioning Trouble - Help

[firecap100]

I have an '04 Mazda 3s and am having some air conditioning trouble.

The compressor was short cycling so I suspected it was just low on refrigerant (r134a). I added a 12 oz. can but the short cycling persisted. I added another 6 oz. with the same result.

I connected a manifold gauge to get high and low readings.

The low side reading is going up and down as suspected thus the cause of the compressor short cycling. The reading rises to 50 PSI at which time the compressor engages and I get really cold air from the vents but then steadily drops to below 20 PSI at which time the compressor shuts off and the cold air goes away. The pressure rises and the cycle repeats.

When I first connected the maniold gauge I was seeing a high side pressure in excess of 400 PSI. Way too high I know, so I removed some refrigerant until the high side was around 250 PSI with the compressor running.

But even with the high side running at 250 PSI with the compressor running the low side is fluctuating up and down between 20 PSI and 50 PSI causing the compressor to short cycle.

I am a new owner of this vehicle but I'm assuming that it is not normal for the compressor to continually short cycle.

Both the evaporator and condenser fans are running normally and the engine temperature is where it should be.

So... any thoughts on what is wrong and where I might start? Are there any common issues with the Mazda 3 air conditioning system that I'm unaware of and should be?

Thanks!
Tom

 

[flatlander937]

Step one: take it somewhere with an HVAC machine to have the system evacuated, vacuumed, and then properly charged.


Step two: there probably won't be a step two because you have it way the **** overcharged. It has an 18oz capacity TOTAL. You added 18oz. It was working beforehand(just not well), so it was probably about 4-5oz low by a guess on my part. So you now have probably 22+oz in it. It probably had a slow/small leak and it may have even been sucking in air causing the bad performance.


Having the A/C overcharged is even worse than undercharged. Keep running it like that and you can kiss your compressor goodbye.





I am a tech and do this everyday for a living... I am not allowed to work on my own cars at work and have to actually pay to have someone else work on it at my work place(kinda sucks... company policy). I never use those stupid rechargable cans that all the backwoods ***** buy to get the A/C working in their piece of s*** Monte Carlo that they claim has 600hp so they can sell it on Craigslist for $12000 with a big rebel flag headliner. It is always worth it to just have the system vacuumed out and recharged with a machine that can measure it accurately.





Oh and welcome to Mazdas 247 Sorry my first post is a bit abrasive.. but seriously those stupid rechargable cans cause more problems than not... I replaced a compressor in a Grand Caravan late last week because the owner didn't want to pay to have someone charge the A/C in it... he overcharged the piss out of it, and burned it up. So by saving $70... he got to benefit of paying roughly $1400 to replace the compressor, the thermostatic expansion valves(front and rear), the receiver/drier, and flushing out both evap cores and the condensor... the compressor bits started eating themselves up due to excessive effort needed to build pressure and sent metal shavings throughout the entire system.

Stepping over dollars to pick up dimes...

 

[firecap100]

WOW... are you a little sensitive or what?

If I thought it was simply overcharged I wouldn't have posted. I will agree that more (yeah way more) refrigerant was added than needed. But... even being overcharged the low side pressure shouldn't be dropping below the low pressure cut off. If anything, it would be higher just like the high side. And as I stated... some of the refrigerant has been evacuated to the point that the high side is running close to the expected pressure.

In reading other posts etc. about Mazda air conditioners I see all kinds of information. There is apparently a TSB out there for some type of diffuser plate to be added to the coils. Other reports indicate the compressor cycles be design.

As the new owner of this particular car... and it being my first Mazda I'm trying to sort through the misinformation and other minutia and figure out what is going on with this system.

I really don't care about overpriced Monte Carlos or damaged Grand Caravans. I realize I overcharged the system... I'm not a moron. I've had some of the refrigerant evacuated to the point where I don't expect there will be any compressor damage until I can figure out what is causing the low side pressure to fluctuate thus making the compressor short cycle. This is why I'm posting... To see if anyone has experience with the Mazda 3 air conditioning system. I'm leaning toward a stuck TXV or other restriction but would like some confirmation before I dig into this any further.

What you don't realize because it isn't germaine to the situation is that I just rebuilt the engine after the previous owner had the unfortunate pleasure of having the oil cartridge housing crack thus relieving the engine of its vital oil. Nothing a new block, piston rod, machined crankshaft, new bearings, new pistion rings, new oil, new coolant, new spark plugs, new seals (front, timing cover, differential), new differential oil, and new belts didn't fix. So I'm not stepping over dollars to pick up dimes. I'm just able to do some things for myself (aka $1000-$1200) to get this car back on the road versus paying the mechanic who quoted the poor guy I picked up the car from $4600 for a used engine and $6000 for a new one.

 

[flatlander937]

WOW... are you a little sensitive or what?

If I thought it was simply overcharged I wouldn't have posted. I will agree that more (yeah way more) refrigerant was added than needed. But... even being overcharged the low side pressure shouldn't be dropping below the low pressure cut off. If anything, it would be higher just like the high side. And as I stated... some of the refrigerant has been evacuated to the point that the high side is running close to the expected pressure.

In reading other posts etc. about Mazda air conditioners I see all kinds of information. There is apparently a TSB out there for some type of diffuser plate to be added to the coils. Other reports indicate the compressor cycles be design.

As the new owner of this particular car... and it being my first Mazda I'm trying to sort through the misinformation and other minutia and figure out what is going on with this system.

I really don't care about overpriced Monte Carlos or damaged Grand Caravans. I realize I overcharged the system... I'm not a moron. I've had some of the refrigerant evacuated to the point where I don't expect there will be any compressor damage until I can figure out what is causing the low side pressure to fluctuate thus making the compressor short cycle. This is why I'm posting... To see if anyone has experience with the Mazda 3 air conditioning system. I'm leaning toward a stuck TXV or other restriction but would like some confirmation before I dig into this any further.

What you don't realize because it isn't germaine to the situation is that I just rebuilt the engine after the previous owner had the unfortunate pleasure of having the oil cartridge housing crack thus relieving the engine of its vital oil. Nothing a new block, piston rod, machined crankshaft, new bearings, new pistion rings, new oil, new coolant, new spark plugs, new seals (front, timing cover, differential), new differential oil, and new belts didn't fix. So I'm not stepping over dollars to pick up dimes. I'm just able to do some things for myself (aka $1000-$1200) to get this car back on the road versus paying the mechanic who quoted the poor guy I picked up the car from $4600 for a used engine and $6000 for a new one.

Sorry dude, been a looong week at work + other stress from buying a house and all that good stuff(jerkit)

Anyways.

If your system was open for any considerable length of time(more than a day)... then I highly recommend you get the system vacuumed down because there is probably a relatively considerable amount of moisture in the system. When this happens, it will have higher pressures than normal, even with the correct amount of refrigerant in the system. So if you evacuate enough out, then you'll end up with just mediocre cooling ability, plus potential damage to stuff down the road.

Also... do you have the manual HVAC system or the automatic HVAC system?


And to clarify... what exactly are your gauges doing now in the following situations:
-Overall pressure with compressor not running(should be same pressures high and low side)
-How high does the high side pressure climb before it cuts off(and how long does it take to do so)?
-Same thing but with low side... how low does it go over how long of a period of time. Is this when it was "fluctuating?"




When a TXV goes bad, it will generally be relatively OK or even stupid-cold for a while, but run the A/C for 15-30min straight and the evaporator will freeze over.

Without knowing anything else, it sounds like your compressor is going bad... this is assuming it is properly charged and no moisture in the system though. When the compressor stops being able to pump, the low side readings will be a bit higher than usual because the compressor can't pull a good suction on it to turn it into high pressure on the other end.


How hot is the line coming off of the A/C compressor? It should be very hot to the touch after a few cycles. How cold is the line going into it(low side)?

Areas of low pressure will be cold, areas of high pressure will be hot. Feel around on the A/C lines to see if there are any places that a temperature change happens where it really shouldn't(or if it should... where it doesn't).

I still think you really need to have the system vacuumed for 30min + and have it properly charged... because either A) it fixes it or B) you can see what the pressures are with a known good system charge and then diagnose accordingly. I know because I've wasted a fair amount of time before trying to diagnose weird A/C issues without confirming the system charge.