Air Conditioning

[smokinmyman]

This is a question you will either know or not know. Cannot guess at it.

1998 Avensis 1800 pre VVTi.

Does anyone know the weight of R134a to fully charge the Air con system?

Cheers

[Solunauk]

I just had my 2.0 CDX AC recharged this morning. The guy at the AA service centre put in 970g, plus some dye (not sure how much dye - could have been 30g). The system was empty (see below) and this was a full charge.

As a follow-up question, does anyone know where the dessicant is? I heard that some Toyotas have a tube of it on the side of the condenser. Is it easy and cheap to change or are we looking at a new drier unit? Also the AA mechanic pointed out a leak around the joint in the sight-glass block that was shown up by the dye he put in. He said there might be a rubber seal in the joint that needs replacing (cheap) or it could be the whole pipe (expensive, no doubt). I'm not sure what to do now - get the leak sorted and definitely have to pay for another recharge, or leave it and see how it goes over the summer. Any advice?

[smokinmyman]

First of all,

thanks Solunauk for your info it was just what I needed to know.

I not an air conditioning expert but I was a refridgeration engineer a few years ago so i understand the principles.

If the AA man is right in that the desicant is in a tube on the side of the condensor then you will need to look in the region of the radiator (the condensor is the bit of the system that gets hot whereas the evaporator is the bit that gets cold and provides the cooling aspect.). My avensis actually has 2 rads, one for the water and one for the air con. They are both the same size and are one in front of the other as you look at the front of the car.

Most other sources on the net seem to suggest that the desicant in more normally in the accumulator which is a container roughly about the size of a coffee mug in the low pressure line(at least on my avensis it is).

I was speaking to a garage mechanic today who recharges air con systems. He showed me a little jar on the side of his machine in which evacuated oil was stored and there was very little in it. He told that the amount in there was from many recharges. The long and short of it was hardly any oil if any is lost in a recharge he says. Hmm I thought , Interesting.

[smokinmyman]

First of all,

thanks Solunauk for your info it was just what I needed to know.

I not an air conditioning expert but I was a refridgeration engineer a few years ago so i understand the principles.

If the AA man is right in that the desicant is in a tube on the side of the condensor then you will need to look in the region of the radiator (the condensor is the bit of the system that gets hot whereas the evaporator is the bit that gets cold and provides the cooling aspect.). My avensis actually has 2 rads, one for the water and one for the air con. They are both the same size and are one in front of the other as you look at the front of the car.

Most other sources on the net seem to suggest that the desicant in more normally in the accumulator which is a container roughly about the size of a coffee mug in the low pressure line(at least on my avensis it is).

I was speaking to a garage mechanic today who recharges air con systems. He showed me a little jar on the side of his machine in which evacuated oil was stored and there was very little in it. He told that the amount in there was from many recharges. The long and short of it was hardly any oil if any is lost in a recharge he says. Hmm I thought , Interesting.

[Solunauk]

Thanks Smokinmyman.

Considering our cars are both 1998 pre VVTI, I imagine the aircon systems are identical. Where exactly will I find the accumulator - I've no idea which bit is the low pressure line? And can the dessicant be changed by the average user, or is it a job for a professional? If the latter then I may have it done when/if I have the leak fixed.

[smokinmyman]

Hi

If you look down on the rad from above to the right between the rad and the Battery but lower down you will see a silvery looking cannistor with a tube going in one end and out of the other, this is the accumulator which i beleive will have the dessicant in it. This is in the low pressure line that then goes along the right hand side of engine compartment into the passenger compartment to under dashboard where the cooling takes place.

It isn,t a job that you can do without the right equipment because if you break into the system in any way air will get in and with the air moisture, when the a/c is running and this moisture get to the evaporator it will freeze and block the system. When servicing the equipment used actually creates a strong vacumn in the system to the point that any moisture "boils" off at room temp because of thr low pressure and is removed. Then the sealed system can be recharged with gas and no air gets in.

i would suggest that if you have just paid to have yours recharged you use it until you notice the coooling effectiveness reduce and the consider having the leak sorted, that way you at least get some use out of your charge and who knows it may be 12 months or more down the line. One other thing when the gas gets below a certain pressure (due to leakage) a pressure operated switch will prevent the compresor clutch from operating and the cooling will cease all of a sudden. So the aircon light is in but the pump is not pumping. Then you definitely will have to gaertit looked at!!

[Solunauk]

Thanks for the advice and information. I will leave it well alone as long as its working!

Sol

[hallsteg]

I have always wondered if my AC (2000 pre VVTi 2.0L) was working OK or not. I find the effectiveness of it very poor in comparison to my Lex GS300. Early on I asked Toyota to check it and they said OK but I was never really convinced. Is there any way for a mechanical numpty like me to check if it is fully charge? How much of a difference does charging make? How much does it cost to get it charged?

[smokinmyman]

Hi Hallsteg

I am going to be recharging my aircon soon , waiting for gas to arrive, and i intend to measure output temp at the air vents when complete, so i will let you know what it is as a comparison.

In the mean time, it costs about £75 - £100 to vac out and recharge at a garage. Car aircon is different to home refrigeration in that a home fridge or freezer has all metal pipework (no leaks) and the compressor is completely sealed to the outside world again = no leaks. Cars on the other hand have some rubber hoses that gradually weep gas and the pump has a seal around the shaft that is belt driven another point of potential leakage. Net result is that a small amount of leakage over time is deemed to be "normal". Most places recommend having a system recharged every 3 years.

Symptoms of a system with reduced gas in it are reduced cooling effect until the system pressure drops below a certain point where a pressure switch prevents the compressor clutch from engaging and the system running.

It is best to have system looked at if there is a noticeable drop in cooling as the gas going round also takes the lubricating oil with it. Reduced gas means reduced lubrication to pump and risk or premature wear.

[smokinmyman]

1998 Toyota Avensis 1.8 Petrol Pre VVTI engine

Ok

I have vac'd out my aircon system, drawn down for 30 mins +, recharged using the guide of 970 grams gas (see previous comment, actually put in 1000 as this is the canistor I had). Slightly overcharged possibly but not by much.

when i turn aircon on clutch engages for less than a second then cycles off and on very rapidly. For diagnosis purposes bypassed pressure switch and almost immediately the compressor vented gas from what i am assuming is a over pressure vent valve, (on back of compressor body). I believe the figure of 970 grams for this model might be an error. Have evacuated small amounts of gas out, the compressor runs for slightly longer now (approx 10 seconds initially, then cycles at about on = 3 secs, off = 10 secs.

When I look into sight glass I cannot see liquid flowing. ( Originally clutch would not engage, but on bypassing pressure switch, ther was no cooling but i could see liquid flowing in sight glass.)

I know for accurate diagnosis I need some guages to measure high and low running pressures, am trying to acquire some as we speak.

What I really need is if somone has access to autodata or similar resources, can you possibly tell me if

1. 970 grams is correct for full charge

2. The running pressures (high and low)

3. The static system pressure.

If anyone can help would be really really gratefull

[smokinmyman]

Just going to add this post for completeness sake so that if in future days somone looks at this they won't be misled.

Previous post stated 970 grams full charge of gas. DO NOT use this amount it is incorrect.

When running the air con with this much in it blew the high pressure relief valve on back of compressor and continued running would have soon killed it.

have found out from an american site dedicated to air con issues that 450 grams is correct and indeed this works fine in my avenses.