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R12 to R134 Church Van won't cool!!!! Pages: 12

Frosty on Thu June 12, 2008 5:19 PM User is offlineView users profile

Year: 1988
Make: Ford
Model: E-350
Engine Size: 351
Refrigerant Type: R134
Ambient Temp: 94
Country of Origin: United States

Hi Folks.

Retro fitted our church van R12 to R134a. HS 200 LS 60 after adding about a can and a little. Compressor seems fine, high side gets super hot accumulator not cold are even cool! Nothing cooling before or after Evap! I put 10oz of PAG. Too much? Van has dual air. Old system didn't crash just leaked bad. Couldn't buy R12 so I changed. Kids leave for camp Monday. Help!!! How many cans of R134 before cooling starts?

brickmason on Thu June 12, 2008 5:28 PM User is offline

1 can wont be enough to even start to get any cooling. Add at least 2 more and then start monitoring the pressures and vent temp. This van should hold around 72 ounces (original r12 charge).

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Just another brick in the wall

Had a little mule I fed him castor oil and every time he jumped the fence he fertilized the soil

Frosty on Thu June 12, 2008 5:33 PM User is offlineView users profile

How high do I let the pressures go?

brickmason on Thu June 12, 2008 5:39 PM User is offline

With adequate air flow across the condenser, expect to see an average of 2.2 to 2.5 times ambient temperature. @ 80 degrees ambient you should see around 250 psi.

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Just another brick in the wall

Had a little mule I fed him castor oil and every time he jumped the fence he fertilized the soil

mk378 on Thu June 12, 2008 5:42 PM User is offline

Like brickmason said, thats a big system, going to take 5 or 6 cans. Don't even bother starting the compressor until you have 3 cans in. But before adding more, there are other issues.

Did you evacuate the system of air first? Find and fix the leak?

PAG reacts chemically with any residual R-12, need to get all the R-12 out which usually means flushing. Even after pulling a vacuum, there's going to be some dissolved in the old oil. Double-end-capped PAG is more stable. Ester oil is preferable for conversions.

The accumulator/drier really must be changed, after 20 years on a leaky system it's bound to be saturated with water and useless. Plus it contains old mineral oil and R-12 residue.

Frosty on Thu June 12, 2008 5:43 PM User is offlineView users profile

Thanks for the reply!

HS is already 200. I don't think it will take two more cans.

mk378 on Thu June 12, 2008 5:47 PM User is offline

Also with a conversion you need all the air on the condenser you can get. With engine driven fans the fan clutch tends to get worn and tired and not spin the fan like it should. This will cause excessive high side pressure that goes down when you cool the condenser with water.

Frosty on Thu June 12, 2008 5:49 PM User is offlineView users profile

I did the whole retro thing. New compressor, accum,orfice tube, fluhed with mineral spirits, denatured alcohol,dried with air hose, fixed all spring connector that were leaking, evaced the system. Added PAG oil 10oz. ?????

bohica2xo on Thu June 12, 2008 6:04 PM User is offline

You can't tell anything with a 25% charge in there. The high side simply reflects the gas pressure right now.

You should check the fan clutch for proper operation, either by misting the condensor with water or using a photocell tach.

On conversions, 2.7x ambient is fine - especially if stopped. The 10 ounces of oil is just fine in a system that big.

B.

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"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

Frosty on Thu June 12, 2008 6:25 PM User is offlineView users profile

Thanks for the replies!
We put a new radiator and fan clutch on last year.

I just added the two more can and praise the Lord it's starting to cool!!!! I sprayed the condenser with the hose to keep the HS down and things are looking up! HS still wants to climb without the water. The HS side best I can tell is 150-200 ish and LS about 30. Vent is 73.

The old sticker on the fan box said 4.5 lbs R12. I figure about 3and a half cans of R134?

Whatda you think?

bohica2xo on Thu June 12, 2008 6:39 PM User is offline

4 or 5 cans is more like it.

The high side will never be 200 psi with a conversion @ 94f ambient. Like I said, 2.7x ambient is ok with a parked conversion.

Run the engine rpm up to 1500, with the cabin fans on highest speed. This is the worst case system load. If you don't hit 275psi @ 94f ambient I would be surprised.

But get some more refrigerant in there first. Then go for a drive & see how it works with some airflow.

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

Frosty on Thu June 12, 2008 9:18 PM User is offlineView users profile

OK Folks,

Added almost five cans total. HS 325 LS 50 Vent 65. However when I drove it I had to stop and jump the low pressure switch!

60Mph down blvd Vent 52.5. Whatdya think, another can? What exactly am I looking for pressurewise?

bohica2xo on Fri June 13, 2008 4:53 AM User is offline

I would stop with the charging, and start looking at airflow over the condensor.

Was that 375 psi at idle, with the evaporator fans on high? At what ambient?

You mention having to jump the cycling switch - was that due to a low pressure condition, or a bad switch?

52 degree vents could be good or bad, depending on the ambient temp & load. With both evaporators running at max blower speed & a hot interior, that is decent on a conversion. If that was the temp with only the front evap running & low fan speed, you have problems.

Go for that 60 mph drive with the gauges taped to the windshield, and see where you are at.

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

Frosty on Fri June 13, 2008 8:04 AM User is offlineView users profile

Well a new day dawns,

Thanks for all the good advice!!!

At about 1500 rpm 24in box fan 94 amb I get 325HS 50LS 63vent. I still have to wet condenser down some to keep low side below 250. If I don't it will go to about 325HS.


I am going to replace the switch today and tape the gauges to the windshield and go for a spin. Hopefully I'll have some better info later.

Thanks for your help.


Frosty on Fri June 13, 2008 8:05 AM User is offlineView users profile

That's High below 250!! Sorry

Edited: Fri June 13, 2008 at 8:06 AM by Frosty

Frosty on Fri June 13, 2008 8:27 AM User is offlineView users profile

Data Update.

Amb 78, 1500 rpm, box fan Hi, switch jumped, both blowers hi, doors open. HS 275 LS 45 Vent 60.

NickD on Fri June 13, 2008 9:07 AM User is offline

Most difficult part is getting that first can in if you have to switch from vacuum hoses to charging hoses, because when you remove a hose, the vacuum in the system wants to suck in air fast, even for a short fraction of a second. And with any air in the system, pressures will skyrocket and cooling will be poor. And always a chance of adding more air if the charging lines are not purged when changing cans, hate cans for that reason because purging is always guess work.

If you can connect your blue line to your vacuum pump, red to the high side, and yellow to the can, can close the valve on the can, open the low and high side valves and draw a deep vacuum all the down to the valve on the can, then close the low side valve blocking the vacuum pump, and opening the can valve to pump in charge into the high side. Making sure the can is much warmer than the AC system will assure most of the refrigerant leaves the can and gets into the system. A four way manifold valve makes life here a lot easier, or steal GMTech's charging system when he is not looking.

Now you have a positive charge in the system where some refrigerant will leak out while rather than air leaking in. Reconnect the blue to the low side, with a new can installed purging first before connecting the low side to the port. A lot's cheaper to buy a tank, and this would void this step, but still have to do that first purge when moving the blue from the pump to the low side port after you got some charge into the system, but with a tank, that charge will be a lot more than a tiny little can.

You charge strictly by the low side, doors open, AC on, blower at max, and 1,500 rpm generally trying to get close to about 28 psi at 85*F ambient, but there are other factors to consider, can hand feel the evaporator outlet until it gets as cold as the inlet or use temperature measuring equipment and compare the numbers. You also can feel pulsations in the inlet hose and want those pulsations to diminish while watching low side pressures. Have to keep an eye on the high side to make sure it's not going through the roof so to speak, at 85*F expect it to be around 250 psi. Another key element is when slowly charging, adding charge no longer decreased the vent temperature, at this point, the accumulator is filling up with a tale-tail sign of the froze level rising, especially on a humid day.

That reminded me of the very first most important step, the air flow paths have to be cleaned first with all fans operating correctly. Normally you can remove the blower motor and check the evaporator fins, you will always find a lot of debris in there and God only knows what else, that has to be clean as well as the radiator and condenser fins. With any air flow blockage, you will never be able to properly charge by pressures and make sure your fan clutch is working.

With higher R-134a pressures will read about 10% higher than R-12 so can't get enough in, have to live with that unless you switch to a parallel flow condenser, more bucks.

You can see where this procedure is greatly simplified by sticking with the OE refrigerant and using a charging station, but can be done also with basic tools, but it takes a lot longer.

bohica2xo on Fri June 13, 2008 2:01 PM User is offline

Nick, thanks for taking the time to type all of that. I was just too lazy to go that deep.

Frosty:

You have plenty of refrigerant in it now, perhaps even a slight overcharge. Take it for a drive & see what the pressures & vent temps look like on the road. If the vent temps drop with more airflow, you need to look at the condensor for gaps etc. where the air could be going around it on the way to the radiator. Cleaning the condensor should be done as well. Does the fan roar on cold start, and then again when hot? At 1500 rpm after ten minutes of idling with the A/C on high & the engine warm - the fan should move enough air to make you check to see if the brake is set.

325 psi on the high side for a dual air conversion is high, but expected in some cases. Your vent temp drop while driving makes the airflow issue stand out. I have seen white box chain store fan clutches crap out in a single summer here in Las Vegas. If you have a dead clutch, you might consider a solid drive fan for a big coling load like that. Tim has them, just not in the online catalog. You can get a lot of cooling from a tube & fin condensor, but it takes a lot of air.

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

GM Tech on Fri June 13, 2008 2:07 PM User is offline

Hey NickD- Check valve connectors on the ends of all three hoses on your gage set make like much easier when not using a machine-- they are sometimes called freezeless connectors etc-- Yellow jacket and Robinaire both sell them-- never lets air in while changing from vacuum pump to charging can......

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The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

Frosty on Fri June 13, 2008 2:18 PM User is offlineView users profile

OK Test Drive Results

60 mph, Amb 90-91, HS 250-275, LS 35-38, vent 55.

45 mph, Amb 90-91, HS 250, LS 40, vent 56.

Both blowers running full.

Edited: Sat June 14, 2008 at 1:12 PM by Frosty

Frosty on Sat June 14, 2008 1:15 PM User is offlineView users profile

Latest on Churh van conversion

Test Drive Results

60 mph, Amb 90-91, HS 250-275, LS 35-38, vent 55.

45 mph, Amb 90-91, HS 250, LS 40, vent 56.

Both front and rear blowers running full.

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