A/C problems

sicksteve

Active Member
In my '73 Riviera GS, the previous owner had the A/C system entirely replaced with a retro-fitter 134a system.

When I had last used it, it blowed ice-cold air (on max-cool)>

Now it just blows ambient-temp air.

I tried charging it to the proper psi (45psi max). When I did, flowing the recharge kit's instructions, I filled it up to 45 psi.

After that I could hear the compressor clutch engage and disengage repeatably--with the psi switching between 25 to 45 psi.

Should the compressor be doing this??

I re-charged another '76 Riv--- with what I believe is the original A/C system, the compressor never engaged/disengaged continuously like the '73's. After charging, it blowed cold.

And though I hate to bring up this car (because many people, including me, are not fond of it), I charged up a Lexus LS400 with the same 134a refrigerant, and it blows cold- w/o the compressor continuously cycling off/on like 1x every second.
 
Where does the 45psi come from. 134a usually is just above ambient air temps depending on temp. and humidity. A 45 psi would have an ambient air temp of about 50 degrees. Is this how cold it was when you were doing it? click here.

When you compressor cycles too quickly, it is usually low.

It is sometimes spec'd that a system should site for up to 12 hours!?!?!? before equalization is sure between the high and low sides.
 
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sicksteve

Active Member
On the can, it mentions the proper range of pressuizations for refrigerant (134a)-- 45pis max, 25psi min.

Why the compressor cycles on/off every sec still alludes me.

And when I accelerate, the air-output stops. I had thought at one time that was du to a slipping compressor belt; it's not--there's a new belt properly tensioned.

Would this be a compressor clutch issue??
 

sicksteve

Active Member
Where does the 45psi come from. 134a usually is just above ambient air temps depending on temp. and humidity. A 45 psi would have an ambient air temp of about 50 degrees. Is this how cold it was when you were doing it? click here.

When you compressor cycles too quickly, it is usually low.

It is sometimes spec'd that a system should site for up to 12 hours!?!?!? before equalization is sure between the high and low sides.
That's for the info. The 45psi cam for the 134a can's requirements for a 134a system. Normal refrigerant pressures are between 25-45psi. It stated to NEVER add more refrigerant to increase psi over that amount.

Also, I read where r12(?) was a much better refrigerant.

When I recharged the system--the air temp outside was ~ 50's F--but even so, Ive had it on max cool at those temps and received freezing cold output.

And why is the compressor cycling on/off every second?

This system was completely re-done using all rebuilt/new components and seals too take 134a refrigerant in 6/06 at a GM dealer by the past owner.

And why would accelerating stop airflow out of the air-conditioning system?

It just seems weird that a compressor clutch would cycle on/off every second, and on my pressure gauage thepsi swings between 45 and 25psi. Should the compressor be replaced?

So, before i start replacing all the parts again, I was wondering what a logical place to begin.

This is bizarre because my '76 Riv--with the original A/C system works well with just one re-charge (i think I stashed a bunch of old cans of the other "environmentally damaging" refrigerant when the Fed's outlawed the good stuff).

But I do need help on this new 134a system. I see that the compressor is marked rebuilt. The inlet and output heater hoses, controlled by a vacuum-controlled restrictor, both seem hot--even with the max cool on. This vacuum-controlled restrictor does seem to work properly: in the Winter, I could adjust different degrees of heat.


Thanks for any help. ( I highlight things because I tend to ramble, and highlighting key questions shows some more respect for the readers who have to read me posts).
 
If it were mine, I would put in another can.

Did you look at the chart I linked to? If the day you charged it was 55 degrees, your static charge should read 58.1 pounds on both sides. It takes time for charge to move and there is differences in the readings of the two gauges so just give it time.

On the high side, 134a often runs at much higher pressures than r12.
 

19RivyRob68

Active Member
:shifter: HI

You will find a switch with wires on the A/C line close to the firewall just before the evaporator----this is why the system cycles. That is normal and is supposed to do that. It cycles because of two reasons---1)if you are too low on refrigerant, then the compressor will not operate (because too low of refrigerant would not circulate the oil in the system thus prematurely wearing out the compressor)----2)to maintain a certain pressure. Once it reaches a certain pressure-it will kick out, then start back up when the pressure is too low for proper cooling. Usually it cycles every few seconds 5-20 depending on the temp. It cycles also for better gas milage, but mainly so it is easier on the system(old systems without the cycling switch would reach pressure of 275 psi on a hot day). The switch is more likely to be faulty.

The reason why the airflow seems to stop (it actually is not stopped) is becuse the vacuum storage tank (for the doors that control vent vs floor vs defrost ) has a one way valve built in which stops the vacuum from leaking when at wide open throttle or even just accelerating half aggressively, which, yours is not working properly. So just replace the vacuum storage tank (usually a small round black container with one larger hose to it (thats from the intake source) and another hose(usually smaller,but not neccessarily) to the vacuum part of the heater/air conditioning switch. Sometimes this one-way valve is just inline on a vacuum hose coming from source(manifold vacuum).

If you are having some vacuum issues, make sure that your temp door is on full cold and you have air coming out of your vent ducts. This may be why you are not having cold air.

If you have any more questions, u can email me at rubberto@shaw.ca

RivyRob :waving:
 
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sicksteve

Active Member
Thanks for the informative help:thumbsup:

Today was change the radiator day. I forgot I had already removed the trans cooler lines and drove 2 blocks over on this abandoned street to work on it. The the car just stopped and wouldn't back-up.

(I can't work on my Buicks at my Loft , but I do late at night in the underground garage)

So I reconnected the lines and got a gallon of trans fluid. Jeez... sometimes I wonder where my mind is at.

Luckily the new 4-core radiator had OEM dimensions ( this was the 3rd--which all listed stock dimensions, but the first two came with completely different dimensions.

It would be cool to have one of those aluminum ones with 1" tubes. 2 rows of that type are more efficient than the regular rectangular row-type.
 

sicksteve

Active Member
:shifter: HI


The reason why the airflow seems to stop (it actually is not stopped) is because the vacuum storage tank (for the doors that control vent vs floor vs defrost ) has a one way valve built in which stops the vacuum from leaking when at wide open throttle or even just accelerating half aggressively, which, yours is not working properly. So just replace the vacuum storage tank (usually a small round black container with one larger hose to it (thats from the intake source) and another hose(usually smaller,but not necessarily) to the vacuum part of the heater/air conditioning switch. Sometimes this one-way valve is just inline on a vacuum hose coming from source(manifold vacuum).

If you are having some vacuum issues, make sure that your temp door is on full cold and you have air coming out of your vent ducts. This may be why you are not having cold air.

If you have any more questions, u can email me at rubberto@shaw.ca

RivyRob :waving:
So that's what that round black thing is for. I noticed most of the vacuum ports capped off. the air only comes out of the top vents when the A/C or MAX A/C are on. With VENT, it blows from below.

The engine runs absolutely great, but when I was waiting for the thermostat to open, putting in 30/70 coolant/distilled water, that compressor cycles at least 1x/sec. I guess I can try to put more in. But why wouldthe pressure gauge say 45psi and drop to 25 and the 45 again?
 

19RivyRob68

Active Member
you definitely are having some vacuum issues---because that water valve that is inline with the heater hoses is to shut the flow of hot coolant to the heater core for max air conditioning----this could be why its not that cold and for the air coming through the ducts inside the car not proper. Rob :waving:
 

sicksteve

Active Member
I did feel the heater hoses (inlet and outlet), and they are both hot with the temp to cool. The vale with with vacuum hose may not be working

But last winter, the hot air was adjustable.

Supposedly,and there are GM stickers and receipts to prove it (along with most of the underside of the dash being empty to facilitate easier access to the new A/C stuff. The old owner won't respond, except to say that, "THAT car cost me way too much!! It was done a GM dealer on 8/2006."

Today, after putting in an new 4-core radiator, I tried adding more coolant--but the PSI needle still kept cycling between 25 to 45 psi. The can stated 45 psi on the low pressure side is the max allowable PSI for coolant.

I would like to know where to get one of those vacuum storage tanks and the check or one-way valve.

There must be something I can do, w/o having to take it to an expensive A/C shop

Thanks for any help,

steve
 

19RivyRob68

Active Member
I did feel the heater hoses (inlet and outlet), and they are both hot with the temp to cool. The vale with with vacuum hose may not be working

But last winter, the hot air was adjustable.

Supposedly,and there are GM stickers and receipts to prove it (along with most of the underside of the dash being empty to facilitate easier access to the new A/C stuff. The old owner won't respond, except to say that, "THAT car cost me way too much!! It was done a GM dealer on 8/2006."

Today, after putting in an new 4-core radiator, I tried adding more coolant--but the PSI needle still kept cycling between 25 to 45 psi. The can stated 45 psi on the low pressure side is the max allowable PSI for coolant.

I would like to know where to get one of those vacuum storage tanks and the check or one-way valve.

There must be something I can do, w/o having to take it to an expensive A/C shop

Thanks for any help,

steve


hi
the water temp valve is not what moves when you adjust for hotter or cooler temp inside the car----that valve gets vacuum to close off the circulation of coolant to the heater core only. do not confuse "coolant" (water/antifreeze) with "refridgerant" R-134 or whatever.

go to any auto salvage yard to get a vacuum storage tank---you can still use yours as long as it isnt cracked, if the one-way valve is not working, just add one inline just before the tank on the hose coming from manifold vacuum source. make sure all vacuum lines are not split at the ends, etc.

You are confusing the engine coolant system with the air conditioning system. The new rad is fine, but has nothing to do with the cycling of the air cond compressor. the more load is put on your air cond system, the longer the compressor will stay running, such as hot days. Since your new to these things---dont worry too much about the numbers ( but that is normal for the pressure to change--thats why they put in the pressure switch in the system, which seems ok)

make sure there is vacuum to your air cond system(I'll call it 'the brain' of your air cond system) to check this--- have the car running and the controls on max air and med or hi fan speed-now go under the hood and pull off the small hose to your water temp valve inline of your heater hoses, and put it to your tongue and feel if there is vacuum there-there should be. that at least tell us if the vacuum to the brain is there, and that it has travelled the distance of its travel to supply vacuum yo the water temp valve.

:waving: Rob
 
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sicksteve

Active Member
Thanks for the help, but no I am not confusing radiator coolant--which was a different issue--not involved with A/C. But the cooling system is working great (all that--EVERYTHING--except for the radiator was replaced last Autumn)

The engine runss so smoothly, I love driving this car. After the ACCEL 71105 e electronic distributor/35366ign moddule/OLD Jacob's Ultra Coil, 300+ wires, and yes (I know, but next year with HEI, it was 0.060"-and my modeule and coilo are much more powerful than stock GM HEI), 0.065" gapped R45TSX plugs

I was putting R134a refrigerant--sorry if I wasn't clear-- to the low-pressure side of the cooling system. Do I need to evacuate the system as I am doing this? It seems not as that the can's directions were clear and I did the same thing to the Lexus--and got cold air back in that car. Some local garage jerk said he wouldn't touch the car, because I had added my own refrigerant (R134a)--and didn't evacuate the system, which was entirely new in 8/06/06.

Anyway, I need the vacuum storage tank. It look fine, but the one-way (check ) valve must be missing, because your info seems right-on. one side looks like it was for a hose, but it seems closed. the other side has the vacuum liner out of it. All vacuum lines are okay. Because almost all are capped--except to the HVAC system, and brake booster.

Thanks again
 

sicksteve

Active Member
I have loooked at all vacuum,lines--which were all replaced when a GM dealer did this "new system" in 8/06/06. The compressor is a "rebuild".

ona different subject, the heater vale (which the vacuum hose does receive vacuum). going on to maxc cool puts the fan on max--like it should, and recroculates inside air--only it is not cool; it's ambient temp.

I think over the winter the fittings contracted and expanded, causinga leak, because the system will not stay ssteading after 2 cans of refrigeant (switching from 25-45psi every second)
 

guyopel

Active Member
Steve your sys. cap. was about 3.5lbs with R 12 and a can was 16 oz . Now they sell R 134 in 12 oz cans . when you convert to R134 you will use less to fill the sys. ( 58oz is now 38 oz ) or 2.5 lbs in the range based on the pressure readings 2.5lbs would be about 3.1 cans of R134 . Your A/C sys. will run at a higher Operating temp. ( Cond. will be hotter so air in front of rad. is hotter ) You can fill your sys. on the low side and it should cool but it is best to have a A/C gauge set so you can read the high and low side pressures to be sure you donot overfill . HTH
John
 
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