[eternalck]

Originally Posted by anupmathur

There is merit in what they are saying. A larger or more efficient condenser will help to a significant degree.
It is important to know the type of evaporator/expansion valve that has been fitted in your car. Is it designed, capacity-wise, for deploying with R12 or R134a?
When you say 'rear shift' of the condenser, where exactly is it going to be located? You should not lose the 'ram' effect of oncoming air with the vehicle travelling at normal speeds.

yes, you are right and to preserve this effect i have decided i will have a 'double condenser' setup, not losing the front cooling of the coil. i've seen the tubes and they are of bridgestone r134a type. the condenser is as big as the radiator and looks just like that of a santro. about the evaporator, well i can't really say anything about that cause i cant have a proper look down there.

but i will only invest in this double setup after i confirm what type of oil, if any, has been used.

if the guy says that he did not put any oil and that the said oil is already in the compressor, i've had it with him and will just demand the money back, since the oil that will be in the compressor would be mineral oil for use with r12.

now about the oil inside the new compressor, when i had looked at he label, i did not find any specifics of any oil inside it, but maybe i wasn't looking properly.
does somebody know here whether this sd507 compressor is sold dry or with oil inside??

[anupmathur]

Found a rather reassuring site:
Sanden (Sankyo) Compressors

Do check; maybe you'll be OK with the one you've got.

[eternalck]

Originally Posted by anupmathur

Found a rather reassuring site:
Sanden (Sankyo) Compressors

Do check; maybe you'll be OK with the one you've got.

hmm, that would solve all my problems!! thanks for searching the site! and it is specifically mentioned that

" charging ports - it IS NOT an indication of compressor compatibility.

^^ The R12 written on the compressor which i saw.

[anupmathur]

Originally Posted by eternalck

hmm, that would solve all my problems!! thanks for searching the site! and it is specifically mentioned that ^^ The R12 written on the compressor which i saw.

Good for you!
Just confirm that the compressor is the 'new' range and not one from old stocks lying with some dealer!

[eternalck]

Well i just checked... and found that it was probably sold dry. its made in japan. on it is written 'oil:.......5GS or equiv.' with no quantity or anything else about it mentioned.

so that just leaves me with the option to go and have the ac taken apart and then filled up from scratch with the refrigerant and the oil.

[eternalck]

so i called up that bloke who installed the damn thing...turns out he doesn't even know that the previous oil is incompatible with r134. what he did tell me before the heated argument that ensued, was that the compressor already has oil.

i went to the other shop i had visited yesterday... he appeared to be much more in terms with all this information and told me that we can take it apart and check out what is wrong.

now on the double condenser part, he told me that the method involves 'jugaad'.. and that they would have to cut and weld tubes to achieve it.

but then now i think how on earth does a normal configuration cool then (as in stock) without the condenser being at the back, which i think is a worse spot for it to be?


but i did have him remove some gas from the system after we found that the low pressure side pressure was reading ~70 on the gauge, whatever its unit is, it started cooling a bit after that. so will removing more gas be of any help? at the end of the removal the low pressure value stood at 60. it was at the time when the ambient temperature was at about 38C.

and i inquired about r12 at many places, and they all say its not available anymore so filling that is out of the question i guess.

[Trust_In_Thrust]

This is for all those who says that M800 condenser at back gives good cooling.
When the condenser is at the back the air ram effect goes for a toss when vehicle is moving .Also the air is blown only from the fans at the rear.Also due to the long distance of refrigerant piping the cooling starts late after AC is switched on.Also compressor has to work harder to pump the refrigerant for such a long distance .This also leads to pressure drop .This all leads to very low efficiency of AC .
I have done everything on my 800 to make the car like a fridge .
So i have decided if time permits i will be fitting a radiator and condenser combo from some other car like accent with slight body modifications in front .Perhaps then the car will be fridge.
I really do not know why the 800 AC do not work like a big car AC .
Wish you all the best with you AC.

[eternalck]

yes trust in thrust the length of the hoses will be quite long and the loss of the front air flow, and the front 120 watt fan replacement going useless are all turning me off to the idea.

anybody know what is the correct way of telling whether a system is overcharged with refrigerant?? is measuring the high/low side pressures the only correct way?

none of the ac mechanics ever checked the high side reading.

and to think that some days ago i was thinking the problem was an undercharge

[anupmathur]

Originally Posted by eternalck

anybody know what is the correct way of telling whether a system is overcharged with refrigerant?? is measuring the high/low side pressures the only correct way?

Measuring the suction pressure when plant is operating at steady state is the best way to ascertain optimal charge.
Discharge pressure fluctuates widely depending on condenser ability/efficiency at that moment.
Though I am not very familiar with typical LP values of R134a, I'd say that 40 to 50 psi seems to be about right.

[eternalck]

ya, after the research and your views anup, i've found that when its 40C outside, the pressure on the low side should be about 40-45psi on the low side and about 250 on the high side.

now i've made an interesting observation, that all these so called 'ac mechanics' are nothing but illiterate joes with little to no information about ac systems, at least around the dwarka area. when i did not know so much about this all, and had gone to a 'mechanic' to have it checked,

1) one of them said that the compressor is 'wrong' (of the r12 type) and will NOT ever cool in the heat with r134a. little wonder that i was feeling like crap then thinking i've sent my money down the drain. whereas now i've found that its only the charging ports which are different (in fact not present on the compressor at all), rest is fully compatible with the new gas. he went on to say that BECAUSE of this compressor there is high pressure all over the system and so it won't cool.

2) one said that the cooling coil (evaporator) is of very low quality, probably trying to sell his stuff. yes it would improve cooling no doubt, but high pressures can't be explained on this basis.

3) 2 others said there is low gas, even the installer, even when the pressure on it was 60psi on the low side, he was filling gas into the system!

4)even day before yesterday's mechanic was no different but he did say that the pressure is too high to cool so why the hell didn't he release some pressure to see what happens (i had to get him to do it)? instead he was just telling me to have the condenser fitted on the back to probably make a quick buck as it would cost me about 4k to get that job done. ok it won't cool that much in bumper to bumper traffic (its 10% lower than R12), but won't be affecting the overall cooling so much.

All of the above observations and conclusions were made after checking the low side pressure that top either on idle or on an insanely fast rpm (i think they would ruin my engine if i go to them a few more times) instead of a steady rpm of 1500.

is getting an ac to work at its optimum such a hardship for all in Delhi, or am i the special one? you can see that i've constantly reported that it was never exactly 'chilling', the only chilling was when the outside temperature also dropped to ~32C.

i've also found that r134a is filled about 15-20% less than r12 would be charged. the reason is what you stated Mr. Anup, that it works on higher discharge pressures and this is done to compensate for the higher pressures. the tubes and coils are all meant for r134a so they would not be stressed out by the higher pressures (and the compressor is the same).

and since the installer was filling gas at 60psi, its no wonder that he already overfilled when installing, thinking 35-40psi is low gas, but anyways he was not checking the pressures when he charged the system for the first time!

now i'm seriously considering buying those gauges and checking everything for myself .

[Trust_In_Thrust]

Well if you want to come to Rohini for the AC there is a very decent AC shop here and it is the biggest here .Turn towards Sector 7 from Madhuban Chowk , Go straight and turn into the bylane next to Gittaratan Jindal Public School.While coming from PeeraGarhi turn left at Madhuban Chowk .On the fourth red light you have the school and the guy has a shop right next to the school in the lane.

[eternalck]

thanks for the tip Trust.. i think i'm gonna go there if things don't work out tomorrow. its judgement day . i will have the man check both the readings after i've pulled the choke a bit (to increase the rpm), then will check the ambient temperature outside the grill, then acording to it will have the pressure adjusted and then cross my fingers if the pressure falls to the correct values, which i firmly believe they would.

[anupmathur]

Eternalck, a car AC operates at constantly varying rpm (capacity) and this makes it rather difficult to ascertain optimal charge status.
That is why makers work on filling a measured quantity of gas by weight.
Could you not check with Maruti how much gas charge is recommended for the M800?

Having done so much of research yourself I dare say you'll be on top of the problem very soon!
Best of luck!

[eternalck]

Originally Posted by anupmathur

Eternalck, a car AC operates at constantly varying rpm (capacity) and this makes it rather difficult to ascertain optimal charge status.
That is why makers work on filling a measured quantity of gas by weight.
Could you not check with Maruti how much gas charge is recommended for the M800?

Having done so much of research yourself I dare say you'll be on top of the problem very soon!
Best of luck!

, thanks...i hope so. i will make sure the rpm stays constant at just above idle to prevent the readings from varying a lot.

I forgot to mention one of their practices, they pour water on the condenser screwing up the readings even more (apart from increasing the engine rpm to insane levels)...and then still when the pressure does not fall to the required range, they do nothing.

the problem with finding out the weight of the gas added by the service centers is that this compressor is bigger than the stock along with the condenser and the evaporator. hence the gas required would probably be more.

[eternalck]

and i found this chart

A/C System Pressure Readings
Ambient Temperature Low Side Pressure High Side Pressure Center Vent Temperature
Low Hi
60 °F 28-38 psi 130-190 psi 44-46 °F
70 °F 30-40 psi 190-220 psi 44-48 °F
80 °F 30-40 psi 190-220 psi 43-48 °F
90 °F 35-40 psi 190-225 psi 44-50 °F
100 °F 40-50 psi 200-250 psi 52-60 °F
110 °F 50-60 psi 250-300 psi 68-74 °F
120 °F 55-65 psi 320-350 psi 70-75 °F

So measuring the ambient temp is very important along with holding the right rpm. and checking only after 10 mins starting it up.