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Discussion Starter #1
Hi All,
1969 Mustang, 351 Cleveland (not original), Edelbrook 600

Just finished the install of my A/C system with the Universal Evaporator from oldairproducts. Systems was vacuumed and charged by the local auto air shop who said that it had a good vacuum on it. The system was the CAP-700 which had 4 vent ports out the top.

I capped off one of the vent holes and ran vents with the other three. It was charged this morning and working ok, but all the sudden is wasn't cooling well and the engine was under the load from the compressor and pinging and knocking.

Anyway, I have found a couple things. Moving the thermostat until the compressor starts and it never goes off. I will sit there and been on until the engine dies I guess.

Anyway, I am confused why the thermostat control doesn't stop the compressor before it becomes a block of ice?

Also, I remember when installing the expansion value that we couldn't get the clip on the sensor on the input to the evaporator, so I am wondering if that could be it?

Anyway, if ya'll got any suggestions, please let me know.

Tosh
 

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A couple of things come to mind but only after you get the clip on the sensor that is near the input of the evaporator. That senses the temperature of the evaporator and cycles the compressor accordingly. Most likely this will correct your problem, the second thing to check is for a proper charge of freon, third and I am sure it probably isn't a problem is make sure there is plenty of airflow through the evaporator. Also get some insulating tape (tar like tape) and wrap the sensor at the evaporator input. Check the temperature of the input and output pipes of the evaporator, they should be within 2 degrees of each other.
 

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Discussion Starter #3
A little more info, if it helps:

I am too tired to get the clip on the sensor off the expansion valve. But, I did go and try it again after adjusting the length of the thermostat wire that goes into the coil. The fitting on the output of the evaporator had ice on it as well as the fitting on the input of the compressor.

Anyway, I will start on it again in the morning. Just a question, on these add-on units, is it fairly common to have these things iceup like this?

Later,
Tosh
 

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It is not common for them to ice up. The compressor has to cycle on and off to maintain a constant temperature at the evaporator. If the thermostat wire (or bulb) is in the coil fins sufficiently to sense the temperature and the compressor isn't cycling as it should then most likely the thermostat is defective and should be replaced...You can probably pick up a similar one at a local parts house...
 
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Just to reiterate, No it definetly should not freeze up. As the previous post said, most likely your problem is because you didnt attach the TXV bulb (Thermostactic Expansion Valve), This regulates the refrigerant flow to a constant superheat (factory preset). The bulb senses the temperature of the outlet (Suction Line) and must also be insulated with cork insulation, without attaching the bulb or insulating it, it will sense the surrounding temp. and end up slugging the compressor with liguid refrigerant (Bad News) possibly ruining the compressor by breaking a reed valve. Blocking up one of the vents isnt good either, but shouldnt be your problem. Attach the bulb and see how it goes, should work. I may not know alot about cars but HVAC is my thing, I do it for a living. I work on anything, big, small whatever, if theres a problem i'll fix it, I dont really work on cars, but when it comes to the refrigerant end its all the same. Good Luck, let me know how it turns out.

SCOTT
65CONV, C-CODE, T10, 4BBL
ITS ALMOST DRIVABLE, WOOOOHOOOO....
 

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Discussion Starter #6
I appreciate it everyone. I am headed down to start to work now. I hope I can get that thing on there without having to recharge it!!!
osh
Later,
T
 

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Discussion Starter #7
Well, I got the expansion value bulb clip on there without too much trouble. I insulated it with that black sticky stuff they sent. Same issue.

If I turn the temperature control to anywhere besides fan only, the compressor comes on constantly and freezes the box. I feel that the expansion valve is installed ok, but anything I might have done wrong on the temperature control?

The manual said to push down from the top two inches into the fin area of the evaporator. I measured two inches and pushed it down in there. Anyway I can check to see if it is working?

Thanks all,
Tosh
 

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Discussion Starter #8
I think I have got it.

I thought of a way to test the thermostat, so I pulled the clutch wire off the compressor and hooked it to my voltage meter and set on the hood. Then I got a glass of ice water and pulled the themostat cable from the box, setting the setting to about half way.

When I turn the ignition to run, my voltage meter said 12.32, and about 5 seconds after I put the thermostat wire into the glass of ice-water, the volt meter read 0.00. So, I knew the thermostat was ok. So obviously, it wasn't getting cold, even when the evaporator box iced up!

What the heck? So, I got to looking at the construction and found the problem, and engineering flaw. The flaw was that the factory hole for the thermostat was in the fins that was right in front of the output of the fans, so as the box freezed it would freeze toward the front and never make the thermostat cold because it was getting air off the intake and not from the coils.

Anyway, I made a new hole in the front of the box and stuck the thermostat in the fins there and immediately got the compressor kicking on and off. About to take a long ride to see how it works.

Thanks to all for the help!!!

Later,
Tosh
 
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