Under Dash Air Questions - The 1947 - Present Chevrolet & GMC Truck Message Board Network

69&72Bowties · 06-06-2002, 04:43 PM

I have a 1972 Cheyene. When I bought it and restored it 1 year ago it came with the under dash air unit. After quizing people about this unit they said it was a dealer option.

Has anyone messed with these before? I cleaned it up and put all new hoses, evaporator, condesor, etc on it along with Charging it with 134A.

The lowest we could get the temp is 56 degrees.. That is no where near cold enough to cool down the cab.. Does anyone know if I need to switch expansion valves to a 134A valve, Or are they the same? I have been told that I need to replace that...

I would like to keep this and use it for the next couple of years... I would love to hear some thoughts from anyone on this issue..

Thanks for your help!

Bryan

Willy Prost · 06-06-2002, 06:00 PM

First thought is did you change the dissicant dryer when you replaced and recharged with 134?

Second thought is to ask the question on
www.aircondition.com
they have a discussion board only dealing with automotive AC.

Yeah, 134 isn't as efficient as 12, but you should be able to get the duct outlet temperature a lot colder than 56 degrees.

69&72Bowties · 06-07-2002, 09:27 AM

The only thing I didnt change with the expansion Valve and any internal components of the Under Dash Unit its self... I changed all of the outside pieces before I had the system charged.

Are there any differences between expansion valves? Is the one I have for R12 and not 134A? I am wondering if the valve is to big and not compressing the 134a enough to make it colder?

I might be out in left field on this, but it was worth a shot!

Bryan

imaindianoutlaw · 06-07-2002, 09:53 AM

Is there a valve in there? Some systems have a cap tube to monitor the refrigerant through. Are you assumming there is a charge problem? You may want to look into a different refrigerant such as hot shot! 414b

69&72Bowties · 06-07-2002, 10:36 AM

Will hot shot work with a 134A compressor? Is it expensive or about the same price at 134A?

I am not familar with it....

Yes I have an expansion valve on the system... It has a temp tube that runs into the system to monitor temps.. (I guess)...

I can get a replacement valve, but I dont know of anybody that knows if there is a difference between the 2?

imaindianoutlaw · 06-07-2002, 11:52 AM

Hot shot is about twice as much as 134a but is more efficient! You cant buy it in the 12 oz cans a far as I know but it works great! How much is the new valve? If it is a replacement valve it should be the same thing? I have never replaced a valve for 134a! I dont know if your valve is adjustable, but thats what I have to do some times! Superheat adjustments on the valve are made to monitor it through the coil. I would have to assujme your valve would be ok with 134a, but I am not working on the system and seeing whats going on?

69&72Bowties · 06-07-2002, 01:47 PM

Okay I have taken my system apart and out of the truck... I have the ex valve in front of me. The part number is 31616 and says R-12-45 on it...

So I am guessing wrong vavle?

69&72Bowties · 06-07-2002, 08:29 PM

I went and picked up a replacement EX valve, but it dont state whether it is for R12 or R134a? It is adjustable, Do I need to adjust it before I install it?

Please help?

06-06-2002, 04:43 PM	#1
69&72Bowties Registered User Join Date: Jun 2002 Location: Pineville, LA Posts: 78	Under Dash Air Questions I have a 1972 Cheyene. When I bought it and restored it 1 year ago it came with the under dash air unit. After quizing people about this unit they said it was a dealer option. Has anyone messed with these before? I cleaned it up and put all new hoses, evaporator, condesor, etc on it along with Charging it with 134A. The lowest we could get the temp is 56 degrees.. That is no where near cold enough to cool down the cab.. Does anyone know if I need to switch expansion valves to a 134A valve, Or are they the same? I have been told that I need to replace that... I would like to keep this and use it for the next couple of years... I would love to hear some thoughts from anyone on this issue.. Thanks for your help! Bryan

06-07-2002, 09:53 AM	#4
imaindianoutlaw GMC SHORT FLEET F/S Join Date: Jun 2000 Location: SOUTH WILLIAMSPORT PENNSYLVANNIA Posts: 2,117	Is there a valve in there? Some systems have a cap tube to monitor the refrigerant through. Are you assumming there is a charge problem? You may want to look into a different refrigerant such as hot shot! 414b __________________ CHARLES WADE HEIN HVACR FOREMAN. LEWISBURG U.S.P.

06-07-2002, 11:52 AM	#6
imaindianoutlaw GMC SHORT FLEET F/S Join Date: Jun 2000 Location: SOUTH WILLIAMSPORT PENNSYLVANNIA Posts: 2,117	Hot shot is about twice as much as 134a but is more efficient! You cant buy it in the 12 oz cans a far as I know but it works great! How much is the new valve? If it is a replacement valve it should be the same thing? I have never replaced a valve for 134a! I dont know if your valve is adjustable, but thats what I have to do some times! Superheat adjustments on the valve are made to monitor it through the coil. I would have to assujme your valve would be ok with 134a, but I am not working on the system and seeing whats going on? __________________ CHARLES WADE HEIN HVACR FOREMAN. LEWISBURG U.S.P.

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06-06-2002, 06:00 PM	#2
Willy Prost Senior Member Join Date: Jan 2000 Location: Arlington, VA Posts: 398	First thought is did you change the dissicant dryer when you replaced and recharged with 134? Second thought is to ask the question on www.aircondition.com they have a discussion board only dealing with automotive AC. Yeah, 134 isn't as efficient as 12, but you should be able to get the duct outlet temperature a lot colder than 56 degrees.

06-07-2002, 09:27 AM	#3
69&72Bowties Registered User Join Date: Jun 2002 Location: Pineville, LA Posts: 78	The only thing I didnt change with the expansion Valve and any internal components of the Under Dash Unit its self... I changed all of the outside pieces before I had the system charged. Are there any differences between expansion valves? Is the one I have for R12 and not 134A? I am wondering if the valve is to big and not compressing the 134a enough to make it colder? I might be out in left field on this, but it was worth a shot! Bryan

06-07-2002, 10:36 AM	#5
69&72Bowties Registered User Join Date: Jun 2002 Location: Pineville, LA Posts: 78	Will hot shot work with a 134A compressor? Is it expensive or about the same price at 134A? I am not familar with it.... Yes I have an expansion valve on the system... It has a temp tube that runs into the system to monitor temps.. (I guess)... I can get a replacement valve, but I dont know of anybody that knows if there is a difference between the 2?

06-07-2002, 01:47 PM	#7
69&72Bowties Registered User Join Date: Jun 2002 Location: Pineville, LA Posts: 78	Okay I have taken my system apart and out of the truck... I have the ex valve in front of me. The part number is 31616 and says R-12-45 on it... So I am guessing wrong vavle?

06-07-2002, 08:29 PM	#8
69&72Bowties Registered User Join Date: Jun 2002 Location: Pineville, LA Posts: 78	I went and picked up a replacement EX valve, but it dont state whether it is for R12 or R134a? It is adjustable, Do I need to adjust it before I install it? Please help?



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