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Discussion Starter #1
I'm a little low on my freon level so i need to add about 1 can's worth to my system. Thing is i couldn't find where the low side port was? I Assume it's the port mounted to the accumulator on my '93 Mark?

If so, i noticed when i turned my A/C on and the clutch cycled intermittently small air bubbles were coming from the area inside the mouth of the port past the check ball. Guess i found the source of my leak.

Thing is if i remove this port my entier system will discharge correct?

If so i'm just gonna dump a can in because i plan on selling the car soon/
 

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if u got a small leak and u just want it to run for when u sell it ,
we did 2 conversions at school 2 old cars that had R-12 and we drained thouse systems one had a small leak and put the R-134 in , they have in that kit one can so it seals small leaks or whatever all i can say is try it i am not sure where it is on a mark 8 but if u have any pics i could point u out or i can check out my friends mark
8 and let u know.


Jurgen
 

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Discussion Starter #3
Thanks. I actually found it today. It's the one located on the accumulator (only fitting my charge hose fit actually)

But i have a problem

I found the A/C clutch cycling on and off a while back. I jump out the low side switch and the clutch stays on continuously. OK, so i must be low on freon.

I hook up my hose to add r-134a and it has a pressure gauge. With the car off i see the pressure in the red at 80-90PSI. Not good. I start the car and turen on the A/C while watching the gauge. Each time the clutch kicked in the pressure would drop and drop down to around 10psi when the switch would cut the clutch out. Then the pressure would climb. Once it got to about 45psi it would kick the compressor in and the pressure would drop again. WHen i shut the car off, the pressure rises to about 60psi and slowly creeps up. If i jump the low pressure switch out and run it continuously, the pressure drops to around 0-10psi and stays there

I've never seen this before. Can anyone ellighten me? Why is the pressure so high when the A/C isn't on but drops like rock when it kicks in.

Do i have bigger problems other than needing a recharge or is this normal and I should look at the pressure when the A/C kicks on.
 

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hey mustang, check your pms would ya? :tongue:
 

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Mustang5L5 said:
Thanks. I actually found it today. It's the one located on the accumulator (only fitting my charge hose fit actually)

But i have a problem

I found the A/C clutch cycling on and off a while back. I jump out the low side switch and the clutch stays on continuously. OK, so i must be low on freon.

I hook up my hose to add r-134a and it has a pressure gauge. With the car off i see the pressure in the red at 80-90PSI. Not good. I start the car and turen on the A/C while watching the gauge. Each time the clutch kicked in the pressure would drop and drop down to around 10psi when the switch would cut the clutch out. Then the pressure would climb. Once it got to about 45psi it would kick the compressor in and the pressure would drop again. WHen i shut the car off, the pressure rises to about 60psi and slowly creeps up. If i jump the low pressure switch out and run it continuously, the pressure drops to around 0-10psi and stays there

I've never seen this before. Can anyone ellighten me? Why is the pressure so high when the A/C isn't on but drops like rock when it kicks in.

Do i have bigger problems other than needing a recharge or is this normal and I should look at the pressure when the A/C kicks on.

Sounds good... if your hooked to the Vapor side ( low pressure side) when the compressor is on the pressure is gonna drop "duh" thats why "refridgerant" (NOT FREON, freon is a name brand of refriderant) works...... The pressure drop is what makes the coils cold, and gives you cold air... When the Compressor stops the entire system goes back into equilibrium and and pressure rises back up...

Some things... What kind of "gauge" are you using does it show pressures or does it have a backplate on the needles to show "temperature" of the refrdgerant..... There should also be 2 pressure switches on the Refridgeration system in your car... A high pressure switch and a low pressure switch... The low pressure switch will activate when there is not enough refriderant in the system to work properly and there should be a high pressure switch so if there is "too much refridgerant" or if there is a blockage the compressor wiil not operate.. .. I've never seen a system with too much refridgerant but I have seem pleny with too much to make "cool air" too much refridgerant in the lines means there isnt as much of a pressure drop across the coils and they dont get as cold.....

And as far as R12 being colder than R134a, i'm not to sure about that the pressures between the 2 are relatively the same... except 134 has no chlorine in it...

You could be like me an run some 409 in there... it is a little cooler :) especially in traffic :)
 

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Discussion Starter #7
Well heres a little more info. I was out on a drive for about 2 hours doing some errands (getting a can of R-134a and picking up some parts for the stang) and it was about 60 degrees out and i was out stetching the DOHC's legs out on the highway so underhood temps were slightly high. The exact static pressure was 80 PSI on the low side under these conditions.

The high side fitting was a little different and i couldn't fit a gauge on it so i only have the low side readings.

Like i said, when i jump out the low side switch to force the compressor to cycle, the pressure drops to 0-5PSI.

After doing a bit of reading, i found the static pressure will always be higher. SO i took a chance and put 1 can in.

After I took readings again after 30 mins or so. Underhood was still warm and my static PSI was still about 80PSI...same as before.

WHen i run the A/C the compressor kicks in for a longer duration of time and holds in the 30-25PSI range. Eventually it drops under 25 or so PSI and the compressor kicks off. So i'm thinking i need a ad bit more refrigerant. WHen i jump the low pressure switch and run it, the pressure is about 20psi and holds. Inside the car i get freezing cold air.

SO i'm thinking i'm fine and need to add maybe 1/2- 1 more cans. It was 60 degrees out and i was inside the car with the windows up freezing my *** off. I'm just worried about my static pressure reading being so high.
 

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I'm far from being an expert but I was curious... and this may help it may not.

The AC test procedure from the Mark manual... paraphrased to save typing errors.

With the system on and stabilized

low side should cycle between 23 and 47 psi. As low pressure drops, high pressure should rise when clutch is engaged. With clutch disengaged high drops, low rises.

Determine clutch cycle rate. 1 cycle = on time in secs+off time in secs.

Record clutch on and off times (seperately)

Record center register discharge temp and ambient temps (seperately)

Then compare all your reading's on the appropriate chart(s). The intersection of the temp and reading lines should be "in the zone".


I know it took me a while to get there but my point was they don't mention the need to check any "static" pressures. I think as long as you don't hear any hissing from lines when the car is off you can probably treat static pressure in this system only as a general indicator. Sounds like maybe you've got it pretty close... and can stop freezing for a bit, if it's low summer temps will let you know it.
 

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It sounds like you are close now. Since you don't have a high side gauge, hold off adding any more, you don't want to run the head pressure up too high. Put a thermometer in the center vent, and let it idle with the blower on LOW(it will be colder this way). If you're around 40 degree outlet temp, you're good.
 

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Discussion Starter #10
Well, i checked again with the car cool and found the pressure to be about 60 PSI now after cooling down to abient temp. The outside temp was about 55 degrees.

If the pressre should be 23-47 PSI then i am just a little low. The cycles are longer but it still kicks off. I'd say i get a good 15-20 seconds befoe the compressor disengauges when the pressure slowly drops below 23psi. If i force it to cycle by jumping the low side switch it hovers around 18-20PSI.

SO maybe i should add 1/2 can to a full can tomorrow? It doesn't get cold enough when it cycles but if i jump it out it's nic and frigid.
 

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Don't force it to run through a cycle..... It cuts on and off to keep the temperatures from getting too low... Plus you gotta remember the outside temp varies from day to day... the compressor will run off and on and keep the air a constant pressure ( temperature ) if it has too much it will not produce good AC if it has too little the compressor will cycle tooo much.. cause the pressures drop too low.. On a VERY hot day the compressor may run different cycles than on a cooler day.... Also make sure you let the engine run for a good while when your doing your testing... dont just power it up and test things...

Also as the inside of the car cools off the pressures will drop. THe more heat that is in the car the more pressure the system will have ( cause its pumping more heat out) when the inside temps get colder the less heat is in the air the lower the pressures will be.... Also you get a better cooling effect when your actually driving down the road... The High pressure side the will go down a lot when you are driving.... 60mph air flowing in the front will cool the condensing coils better than a fan ever will....

I guess what I'm getting at is there is no absolutely correct number... you should shoot for.... Thats what they have high and low pressure switches it keeps the coolent in a range of pressure that work. Drive it down the highway a bit and see how she cools, if it cools good leave it alone.....

another thing you need to consider is that you have a leak! leaks never get better they only get worse... I suggest finding the leak because it wont be long you'll be puttig more refridgerant in that system :(
 

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Discussion Starter #12
Jason said:
another thing you need to consider is that you have a leak! leaks never get better they only get worse... I suggest finding the leak because it wont be long you'll be puttig more refridgerant in that system :(
Yeah, normally i would troubleshoot that but like i said i plan on selling the car within a month or two so i just want to get it cold and ran a little stop-leak
 
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