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high reading on low side, cant charge

RitcheyAuto on Fri May 23, 2008 12:45 PM User is offline

Year: 1991
Make: Dodge
Model: truck
Engine Size: 5.9
Refrigerant Type: Freeze 12
Ambient Temp: 85
Pressure Low: 90
Pressure High: 120
Country of Origin: United States

Truck had same symptoms before we replaced the expansion valve and compressor. I first put the gauges on it and it had around 85 on the low and 110 on the high side but I only recovered about 1 Lb of refrigerant. Put on a new (not reman) C171 compressor and a new expansion valve. It only pulls down to 25 in vacuum but does hold it. I can only get 1 can of refrigerant in there and then the low side pressure gets up too high to pull in any more. The pressures do NOT change with RPM. Stumped, any ideas would be great! Thanks, John.

TRB on Fri May 23, 2008 4:20 PM User is offlineView users profile

Sounds a lot like a restriction. Anyone add sealer to this vehicle? Compressor failure in the past?

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RitcheyAuto on Fri May 23, 2008 5:46 PM User is offline

It did have a reman compressor on it and it smoked the clutch. Wouldn't a restriction make the high side high and the low side low? I am not sure if anyone has added sealer.

TRB on Fri May 23, 2008 6:04 PM User is offlineView users profile

Depends where the restriction is located.

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RitcheyAuto on Fri May 23, 2008 6:24 PM User is offline

I see. So with these symptoms, where (and how) is the best place to start looking?

TRB on Fri May 23, 2008 8:56 PM User is offlineView users profile

I would start by disconnecting each component and blowing nitrogen trough the item checking for a restriction. If you have some cooling, you may want to check the different sections of the condenser for cold spots before pulling the refrigerant.

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Dougflas on Sat May 24, 2008 8:27 AM User is offline

If you have an "H" valve TXV, give it a smack with the back of a large screwdriver while the compressor is pumping. I had a new TXV stuck shut. It worked forever after that.

Chick on Sat May 24, 2008 9:21 PM User is offlineView users profile

Did you change the drier? feel the lines going into and out of it, should be the same temp..

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

iceman2555 on Sun May 25, 2008 12:02 AM User is offlineView users profile

"Ya kant pump,what ya aint got".
Seems as if there is insufficient refrigerant in the system...try 'forcing' refrigerant into the system....place the cans into a container of warm water....raise the internal can pressures to force refrigerant into the system. Correction...this method is not such a good idea with Freeze 12....see statement below about liquid charging.
The best and true method would be to use a recharge machine to meter the correct amount of refrigerant.
Especially since....Freeze12 should be charged as a 'liquid'.....charging as a vapor may result in an imbalance of chemicals and possible cooling/lubricant problems.
If my memory serves me correctly....are the service ports near or at the compressor manifold?
Since the condition existed prior to the compressor installation and the system only had 1lb of refrigerant....recovered...how....a separate recovery machine....hopefully a dedicated machine for this blended refrigerant .......and Freeze12 can not of should not be recycled.....use only once.....possible imbalance problem again.
The size of this system will 'hold' a can (1 lb ?) and not have sufficient refrigerant to function.
Get the thing charged correctly....think 134 would be a better refrigerant choice....and it should work well with this vehicle.....large condenser....good cooling....at least you can use the stuff over and over.....why the decision for a blended refrigerant?
Do not think there is a restriction.....could be...but the condenser on this vehicle is a large tube 12 type....very difficult to severely restrict refrigerant flow....the evap may not be subjected to sufficient refrigerant to result in any cooling....thus the TXV can not begin to operate...thus no or very little high/low side pressure differences.....the screwdriver tap...may work.....but the system should be properly recharged first.
Also, wonder how long the system has been operational with a possible lubricant flow problem.....does not take very long for a compressor to suffer serious internal damage due to lack of lubricant flow.....and lubricant flow is dictated by the amount of refrigerant within the system......how was the system cleaned prior to compressor installation...how was lubricant added to the system.....what type and how much.......

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RitcheyAuto on Wed May 28, 2008 9:45 AM User is offline

I somtimes use the freeze 12 because a decent portion of the the r134a conversions I have done in the past just didnt get cold enough. This vehicle recently had a reman compressor on it with no conversion fittings so I asssumed it wasnt R12 or R134a. I did smack the TXV a couple times but no improvement. This compressor is actually down by the frame rail and the fittings are up by the condenser inlet and the TXV. You can see flow through the sight glass and it actually was dripping water from the evap. None of the other lines were sweating.

CCWKen on Wed May 28, 2008 6:28 PM User is offlineView users profile

What kind of "flow" do you see in the sight glass?

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Ken Kopsky

Custom Car Works
"Rules are for the guidance of wise men and the obedience of fools."

RitcheyAuto on Wed May 28, 2008 6:31 PM User is offline

It looks cloudy but you can see it moving through the glass.

TRB on Thu May 29, 2008 12:17 AM User is offlineView users profile

Check for cool spots on the condenser compared to the other sections. You should have a normal temp drop from top to bottom but look for something odd. You can still have flow with this style condenser yet have restrictive passages.



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