Author Topic: AC temp at vent?  (Read 137 times)

Amigo-2k

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AC temp at vent?
« on: June 07, 2019, 07:45:44 AM »
I stuck a temp probe in the ac vent and let is sit for 5 mins with the car running and it is at 55 deg.  My Subaru is at 40.

My TA has a new age compressor and the rest of it is the old 1977 parts.

thoughts on my temp?

Also, I don't have any condensation under the TA from the AC
1977 TA - LS1 swapped

81Blackbird

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Re: AC temp at vent?
« Reply #1 on: June 07, 2019, 11:21:47 AM »
Both Grand73Am and myself talked about this about a week ago.  I have all the OEM parts except for the compressor.  He has a new system.  We ran both our cars at 55-60 MPH.  I was getting 41 at the center vents.  He was getting higher but has made a few mods to bring it down.  One was to put a shut off valve on one heater line witch we both did.  I made a koozie for the dryer.   Both of us also have a VOT installed.  I did my test on a 81*F day.  I don't remember Grand73AM condition on his test run.  I bet he is typing right now....

Amigo-2k

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Re: AC temp at vent?
« Reply #2 on: June 07, 2019, 12:54:26 PM »
What is VOT?
1977 TA - LS1 swapped

81Blackbird

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Re: AC temp at vent?
« Reply #3 on: June 07, 2019, 01:46:43 PM »
Sorry.... VOT is a variable orifice tube.  Unlike the OEM style which doesn't reduce the flow of Freon, this one has a small valve the restricts the flow of Freon at idle.  The R-134a is not as efficient as the R-12 and therefore needs extra time to cool in the condenser.  As the pressure builds, off idle and cruise, the valve is forced open and the Freon flows freely since there is more air moving over the condenser.  These VOT's, from what I understand, comes with the new system.  I am running an old system so all I had to do was order one when the system was ready to be charged.  And when I say the 134a is not as efficient as the R-12 I'm talking about the conversions.  My 97 Ranger has the 134a and it will freeze you out even on a hot day.

Grand73Am

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Re: AC temp at vent?
« Reply #4 on: June 07, 2019, 06:31:08 PM »
Both Grand73Am and myself talked about this about a week ago.  I have all the OEM parts except for the compressor.  He has a new system.  We ran both our cars at 55-60 MPH.  I was getting 41 at the center vents.  He was getting higher but has made a few mods to bring it down.  One was to put a shut off valve on one heater line witch we both did.  I made a koozie for the dryer.   Both of us also have a VOT installed.  I did my test on a 81*F day.  I don't remember Grand73AM condition on his test run.  I bet he is typing right now....

I have a Classic Auto Air 134a setup with everything under the hood new. I was disappointed that it didn't get colder. So, I did a test run to see if adding a heater shut-off valve in a heater hose would help. It's was an 87 degree day. At 55-60 mph steady driving, I got 44.4 degrees at the vent with the heater hose shut off. After opening the hose, on the same drive, temps went up to 48.4. So, the valve was good for a 4 degree cooler air. So, that's a worthwhile thing to do. I put the valve on the 5/8 heater hose.

Other things to check are for air leaks around the evaporator box on the firewall, so no warm air is getting inside, and make sure the blend door in the heater box under the dash is closing fully in the cold position. It's operated by a cable. Running the air on "max" gets you the coldest air, since it recirculates interior air. Your vacuum valves have to be working for the doors to move to the correct positions.
Steve F.

Re: AC temp at vent?
« Reply #4 on: June 07, 2019, 06:31:08 PM »

Aus78Formula

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Re: AC temp at vent?
« Reply #5 on: June 09, 2019, 05:13:44 AM »
When I first did my custom AC setup based on an extended original with R134a, we measured 39 (4) degrees at the vents. But then the drier and pressure switches started to freeze up. Had to wait for it to defrost before we could adjust it slightly and had it at about 45 (7) degrees. That was in the middle of summer, the full vents were not in place but about 3' of ducting from heater box. That was a few years ago and it has since leaked. Need to regas, find leaks and try again with a few mods.

One thing I noticed was that without the ducting piece, the condensation would drip directly below the heater box onto the floor, no carpet. When redone later, with ducting, it didn't appear to form as much. I guess the cold vs hot sudden change wasn't as drastic. It's one thing I need to test and modify next time, don't want to ruin new carpet.
« Last Edit: June 09, 2019, 05:18:30 AM by Aus78Formula »

Grand73Am

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Re: AC temp at vent?
« Reply #6 on: June 09, 2019, 06:12:37 AM »


One thing I noticed was that without the ducting piece, the condensation would drip directly below the heater box onto the floor, no carpet. When redone later, with ducting, it didn't appear to form as much. I guess the cold vs hot sudden change wasn't as drastic. It's one thing I need to test and modify next time, don't want to ruin new carpet.

If your evap core is still in a case on the firewall, there's a drain hole in the bottom of the case, so it should drain the condensation outside, not inside.
Steve F.

Aus78Formula

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Re: AC temp at vent?
« Reply #7 on: June 09, 2019, 07:11:41 AM »
Yes, mine is custom but has hole. Wanted to make sure it was large enough and not blocked by sealant. The condensation was on the box itself, not dripping from it. One day.

Re: AC temp at vent?
« Reply #7 on: June 09, 2019, 07:11:41 AM »
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