Any A/C experts

[Learpilot]

My vent temp is around 42 at slow speeds , but climbs to  52 at hwy speeds 65 mph. When I slow down the vent temp will return to 42.
Any Idea ?  Is this Normal ?
I have the smallest  Southern Rod unit under my dash. I have there Condenser a sanden compressor. I am currently running r-12 but it was the same with r-134.

THANKS FOR YOUR INFO !

[wayne petty]

just curious... is there more air going through the evaporator at highway speeds....     faster airflow.. less time to remove heat...

what sort of pressure readings?  too much in the system.. preventing the low pressure from getting low enough to properly cool....

perhaps too small a metering orfice?? systems are tested with a big fan blowing across the condenser to simulate ram air... so techs can measure temps with a non contact temp gun...

is there any way to create more ram air through the condenser... rubber strips blocking any exit except through the condenser and radiator for air flow through the grill....

[papastoyss]

My vent temp is around 42 at slow speeds , but climbs to  52 at hwy speeds 65 mph. When I slow down the vent temp will return to 42.
Any Idea ?  Is this Normal ?
I have the smallest  Southern Rod unit under my dash. I have there Condenser a sanden compressor. I am currently running r-12 but it was the same with r-134.

THANKS FOR YOUR INFO !

I had the largest Southern Rods unit in my 47 Ford coupe & it wouldn't cool my FA . I swapped it out for the largest Vintage Air unit w/ the same compressor & condenser & now I can't leave it on high once the car cools down. How much insulation do you have?That makes a big difference.

[Learpilot]

just curious... is there more air going through the evaporator at highway speeds....     faster airflow.. less time to remove heat...

what sort of pressure readings?  too much in the system.. preventing the low pressure from getting low enough to properly cool....

perhaps too small a metering orfice?? systems are tested with a big fan blowing across the condenser to simulate ram air... so techs can measure temps with a non contact temp gun...

is there any way to create more ram air through the condenser... rubber strips blocking any exit except through the condenser and radiator for air flow through the grill....

I have a 12" electric fan mounted to the condencor that comes on with the compressor.  I have 28 oz of r-12 that is recommended by Southern Air.
The pressures look normal to me they are about the same as a chart that is in the Haynes A/C book. I can get a new reading. What rpm should use to get the reading ? I will record the OAT and Humidity. My elevation is 400'.
I have good insulation. Two layers of aluminum bubble all over except the doors which has one layer.

[Learpilot]

just curious... is there more air going through the evaporator at highway speeds....     faster airflow.. less time to remove heat...

what sort of pressure readings?  too much in the system.. preventing the low pressure from getting low enough to properly cool....

perhaps too small a metering orfice?? systems are tested with a big fan blowing across the condenser to simulate ram air... so techs can measure temps with a non contact temp gun...

is there any way to create more ram air through the condenser... rubber strips blocking any exit except through the condenser and radiator for air flow through the grill....

I went to the Garage and got some numbers.
First the Weather Temp 91 Dewpoint 69 Humidity 51% Baro 29.97 Density Altitude 2600' Elevation 400'.
At Idle Low 23 psi High 195 psi.
At 2000 rpm Low 15 psi High 200 psi.

THANKS !!!

I have a 12" electric fan mounted to the condencor that comes on with the compressor.  I have 28 oz of r-12 that is recommended by Southern Air.
The pressures look normal to me they are about the same as a chart that is in the Haynes A/C book. I can get a new reading. What rpm should use to get the reading ? I will record the OAT and Humidity. My elevation is 400'.
I have good insulation. Two layers of aluminum bubble all over except the doors which has one layer.

[Learpilot]

just curious... is there more air going through the evaporator at highway speeds....     faster airflow.. less time to remove heat...

what sort of pressure readings?  too much in the system.. preventing the low pressure from getting low enough to properly cool....

perhaps too small a metering orfice?? systems are tested with a big fan blowing across the condenser to simulate ram air... so techs can measure temps with a non contact temp gun...

is there any way to create more ram air through the condenser... rubber strips blocking any exit except through the condenser and radiator for air flow through the grill....

I went to the Garage and got some numbers.
First the Weather Temp 91 Dewpoint 69 Humidity 51% Baro 29.97 Density Altitude 2600' Elevation 400'.
At Idle Low 23 psi High 195 psi.
At 2000 rpm Low 15 psi High 200 psi.

THANKS !!!

[enjenjo]

Pressures sound a bit low for R12.

[papastoyss]

Another thing or too. Is any outside air filtering in around doors or thru trunk? Is your exhaust close to floorboards?I have found the insulation that is closed cell foam w/ foil on both sides is much better than foil/bubble wrap.Unfortunately it is hard to find. I think maybe lobucrods on the hamb might  have this stuff.

[Learpilot]

Another thing or too. Is any outside air filtering in around doors or thru trunk? Is your exhaust close to floorboards?I have found the insulation that is closed cell foam w/ foil on both sides is much better than foil/bubble wrap.Unfortunately it is hard to find. I think maybe lobucrods on the hamb might  have this stuff.

If it is low does that mean I need more freon ?

I got the doors and trunk sealed ok. There are always going to be air leaks.
Where did you get that closed cell insulation ? That sounds like I need some of that.

[enjenjo]

If it is low does that mean I need more freon ?  

Yes. 28 oz is just a guideline. R12 you should really have a sight glass to charge with, charge until you eliminate the bubbles in the sight glass. If you charge with pressures, I like to see at least the high 20s on the low side, I don't get concerned until the high side is over 250.

That said, I am not impressed with Southern Air units, they are marginal at best in a coupe, useless in a sedan. they might be ok in a pickup if it's insulated good.

[Learpilot]

If it is low does that mean I need more freon ?  

Yes. 28 oz is just a guideline. R12 you should really have a sight glass to charge with, charge until you eliminate the bubbles in the sight glass. If you charge with pressures, I like to see at least the high 20s on the low side, I don't get concerned until the high side is over 250.

That said, I am not impressed with Southern Air units, they are marginal at best in a coupe, useless in a sedan. they might be ok in a pickup if it's insulated good.

THANKS !!!!!!!

[tomslik]

If it is low does that mean I need more freon ?  

Yes. 28 oz is just a guideline. R12 you should really have a sight glass to charge with, charge until you eliminate the bubbles in the sight glass. If you charge with pressures, I like to see at least the high 20s on the low side, I don't get concerned until the high side is over 250.

That said, I am not impressed with Southern Air units, they are marginal at best in a coupe, useless in a sedan. they might be ok in a pickup if it's insulated good.

S.A is marginal cooling the box they came in....no love from me...
but the pressures sound too low to me, too.
add mo freon..

[Learpilot]

If it is low does that mean I need more freon ?  

Yes. 28 oz is just a guideline. R12 you should really have a sight glass to charge with, charge until you eliminate the bubbles in the sight glass. If you charge with pressures, I like to see at least the high 20s on the low side, I don't get concerned until the high side is over 250.

That said, I am not impressed with Southern Air units, they are marginal at best in a coupe, useless in a sedan. they might be ok in a pickup if it's insulated good.

S.A is marginal cooling the box they came in....no love from me...
but the pressures sound too low to me, too.
add mo freon..

THANKS !!!

[Okiedokie]

I have one of the Southern Air units in my 46 Ford coupe. Never again, does a lousy job and I have never met anyone who liked theirs. I put Vintage Air in my 53 F100 and it is great. Joe

[The Paisano]

Does your car have clucth on the radiator fan?If so,rev the engine and look at the fan,if it slows down cosiderably,that's probably your problem.
Its not cooling the condensor fast enough to condense what's coming out of the compressor,high pressure hot gas.The other cosideration is if you have a receiver dryer unit instead of an accumalator,the dyer is partially restricted,with drying material.A lot of these dryers when they are wore out,will send the drying pellets which are inside a sack out to rest rest of the system and restrict the expansion valve,and possibly other components.
I used to see this happen all the time.What happens there is that the condensed hot liquid coming out of the condensor is filling the dryer faster than it can come out,causing a restriction.
Paisano