too much r-134a ?

[Hoot]

hello all, it has been a long time since i have posted and knock on wood a long time since i have had any problems with the disco, but just as i thought that. BINGO. AC is acting weird. I usually don't even turn the thing on but we have a new little in the house and when on the road we need to keep her and the wife cool. So in an effort to be proactive i bought a can of AC coolant refill. the r-134a kind. ( i have a 96 Disco SE by the way) and that recharge can did not do much it was the small can so i figured it was not enough as i have owned the disco for 3.5 years and not added any r-134a to it and i doubt the last owner did either (she was a soccer mom)

so i figured i should try another can. i bought one of the cans that have the attached pressure gauge so that i could be sure that i did not over do it. I turned the truck on and the ac on high and had a hell of a time getting to quick release refill hose to attach to it, it drove me nuts. and then a i dropped the cap to the low pressure coolant cover behind the washer fluid reservoir never to be seen again. so as i am refilling it i hear the compressor motor click on and off a bunch of times and then i go to the front and watch the ac compressor clutch click on and off and now the ac is blowing warmer then when i started. wtf.

i consulted the D1WorkshopManual.pdf and it said to be careful of adding too much pressure to the system as it could cause "excessive head pressure" do they mean the cylinder head? am i stupid? what head?

does anyone have any suggestions on what the heck might be wrong here? The compressor unit may well have been doing this for along time and i never have the AC on when i am under the hood and you an not hear it click on and off form inside the cabin.

It is hot as hell here in Oakland, CA and my wife and baby are going to suffer and thus I will suffer. Please help me and my baby girl out any suggestions would be appreciated.

 

[jhmover]

Excessive head pressure I believe is enough pressure in the system where the piston can't cycle in the compressor. I just converted my son's Volvo to R134, they caution not to put too much in it, the guy I had charge it put in about 90% of full, he said anything more would cause problems, but didn't elaborate. That's probably why.

 

[Phototone]

The air conditioner compressor has pistons and a "head" where the R134a is compressed. That is the "head" you have to worry about. The A/C compressor compresses the R134a, and then it goes to the evaporator coil inside the car where it expands thru an oriface, it is the rapid expansion of the compressed gas that absorbs heat from the air in the car that is circulated over the coil by the interior fan. The refrigerant (now expanded and carrying the absorbed heat) goes to the condenser coil (in front of the radiator) where the absorbed heat is radiated into the outside atmosphere by the forward motion of the car and the electric fans that blow across the coil. The R134a then returns to the compressor and gets compressed again. It is a continuous cycle. So actually modern air conditioning is just a process of moving heat from inside the car to outside the car. I am not a big fan of "top up" kits, because the act of trying to attach the hose to the system can cause a lot of air to be sucked up inside the sealed system, thus radically lowering the efficiency of the cooling. A/C shops do not charge very much for a service, and in fact, Wal-Mart used to do A/C service and may still. Your Disco a/c is not "special", as they all work the same. By having an A/C shop put their test guages on the car, they can immediately tell if it is low on R134a or if there is another problem. If they have to do any repair, they pump out and capture your R134a for re-use, and you only pay for the additional R134a needed to "top up".

As an additional comment...My 99 Cadillac, which I purchased new in 1999 has never needed any R134a, and it still cools like new. It is not wise to just "assume" that when Auto A/C doesn't work that it is the R134a needing "topping up."

 

[Ed Cheung]

If u need to re-charge the r-134a, don't you know there is a leak somewhere, as it suppose to be a close system.

 

[p m]

If u need to re-charge the r-134a, don't you know there is a leak somewhere, as it suppose to be a close system.

It is a "close system" all right, but time does wonders.
FWIW, my 96 D1's AC still works, never been serviced, although it could probably use some more R134.

 

[Phototone]

It is a closed system, and can work fine for decades "IF" you remember to cycle it on once a week to lubricate the seals. If you do not use the A/C for months, the compressor seals dry out and will gradually seep R134a. Also, due to the nature of the compressor being mounted on the engine, it has to have rubber hoses to connect it to the frame and chassis mounted parts, due to engine flex, and these rubber hoses, even though they are very robust and designed for the job, do leak at some point in their life, particularly as they grow old. It is fairly safe to say that if you have enough of a loss of R134a to compromise the cooling capacity of the system, then you really need to renew the compressor seals and rubber hoses and "O" ring pipe fitting seals.

My particular Disco1, a 1994 which I purchased a few months ago as a "fixer-upper" hadn't been licensed since 2005, yet it only needed 1/2 pound of R134a to be fully charged.

I should mention that all the perishable parts on any auto air conditioning are common and can be replaced or renewed by any shop that does Auto A/C work. Nothing is Rover specific in the R134a system.

 

[Ed Cheung]

My thinking is that will the re-charge last a season if there is a leak as 134a is in a pressurize system.

 

[Hoot]

update. i think my problem was that i had over pressurized the system with the DIY recharge canister. So i had to go in and just let some of the gas out using the Low side access valve, much like you would let air out of the tire. I know that this is a shit way to have done it and a hack job and i will get it serviced this week but i figured it was better then running her with too much pressure and frying the compressor unit out.

thanks for all of your help.

 

[Phototone]

My thinking is that will the re-charge last a season if there is a leak as 134a is in a pressurize system.

That is totally dependent on the size of your leak. If it was leaking thru compressor seals due to NOT running it briefly every week during the winter, then it is possible that the constant running you would be doing in the summer months would re-lubricate the seals and the "leak" would be minimized, at least for the summer.