Any A/C experts ?

[Learpilot]

I am running a Sanden Compressor with a Walker Radiator and condenser. The pressures are right on the money as my A/C books says.
My vent temps are 45 to 50 degrees with outside temps 90 to 95 with a lot of humidity with my engine rpm below 1700. When I speed up to cursing speed of 2000 to 2200 rpms the vent temp will climb up to 60 degrees. I am using R143. I have my firewall well insulated. I thought that with my hood sides being on may be not venting enough engine heat. Today I took them off to get rid of the under hood heat. No difference. When I slow down to a red light my vent temps fall back to 45 to 50 degrees.
I have a SBC with a set of stock '68 327 pulleys. The crank pulley is larger than the waterpump. I have no problems with engine temp and it stays at 180.
I was thinking about putting some aluminum pulleys (I have a new set that I have never used) that the crank is smaller than the steel ones and the waterpump is the same size as the crank.
My thinking is that at the higher rpms that is pushing the Freon too fast for heat transfer, very similar to pushing water through the radiator.
Thanks for your answers !!!
Rick

[wayne petty]

was not there a thread on this or a similar problem about 2 years ago..

were the temp switch  that controls the compressor clutch by evaporator temp...

i don't specialize in ac...  i try to avoid it..  i just cannot remember the name of that part.. but i hope somebody else remembers that thread..

it cured the problem...    with a change in that switch...


the switch turns off the compressor when the temp gets down to a preset point.. that is too warm...

[enjenjo]

Any way to get your pressures cruising down the road? The freon moving too fast is a non issue, the expansion valve/ orfice tube controls the speed that it moves through the system, if there is enough in there.

[reborn55]

Hot water valve not shutting off, possible dirt in orifice tube, filter screen.

[Learpilot]

Hot water valve not shutting off, possible dirt in orifice tube, filter screen.[/quote
I have a water shut-off valve on the waterpump. I know it it the return but it can not flow with the valve closed. I don't think I  could ever get 45 degrees vent temp with any water leaking.
Thanks for the info about the expansion valve.
Would low freon give me 45 degrees vent temp at low compressor rpm ?
When I put the freon (R-134) by weight not by cans.
THANKS ,Rick

[wayne petty]

just curious...

does the compressor clutch cycle off when the temp gets down to 45F?

it should cut off if the proper controller / temp switch is installed... at 21F..

this would cool your interior better...

just curious.. did it ever work right??   putting out  vent temps in the low 20's ...


i was trying to download some AC parts catalogs.. but they have not shown up yet...

[reborn55]

Ragtop and personal truck will cool right around 40 degrees constantly

Temperatures in the 20's woudl just cause the evaporator to freeze up even if it cycles.  Very hard to get into the 20's at the vent even using R-12.

Just my .02

[Learpilot]

just curious...

does the compressor clutch cycle off when the temp gets down to 45F?

it should cut off if the proper controller / temp switch is installed... at 21F..

this would cool your interior better...

just curious.. did it ever work right??   putting out  vent temps in the low 20's ...


i was trying to download some AC parts catalogs.. but they have not shown up yet...

The compressor will cycle when the air temps are around 70 and below, but at 90 to 95 I don't think so. The clutch may be cycling at highways speed but I can't be sure. I have a everything new as of last spring and it has always done the same thing with my other a/c unit. That was before I re insulated the firewall. I have a Southern air Maxi 4 all electric evaprator. That is the biggest one that I can get under the dash of my 36 Dodge coupe.
lIf I bypassed the compressor temp switch would that be ok just to test to see if it is bad. I don't think that the evaproator is freezing up because the air flow is the same.
Rick

[ONE37TUDOR]

I had that same issue with my unit and found that the belt (I only have one on it) was bottoming out in the v grove and let the compressor slip at speed.
Just something to check?

Scott...

[UGLY OLDS]

Try backing the temp control DOWN approx 1/8 of a turn ....Road Test ...If no change back down 1/4 turn ...Road test ...At highway speeds the system should "cycle" the compressor on & off after initial cool down .....
Southern air units are famous for freezing at the expansion valve.....  (I'm not knocking them ..They had issues in the past but have gotten better) ....

How long was the system under vacuum before charging ??  Moisture in the system is what freezes at the expansion valve ..The longer the system is under vacuum the more moisture gets "boiled" out ...I try to leave the system under vacuum for at least 1 hour with a 150 watt droplight hanging on the dryer to "raise" the boiling temp of the moisture trapped in the descant bag ......

What kind of pressures at 1500 rpm parked with a BIG fan in front of the radiator???   Believe it or not I use a furnace squirrel cage blower for diag A/C systems when the car is not moving ....Condensers like LOTS of air moving across them  .....

Also check to verify that your condenser is sealed to the grille shell ....
IE: No open spaces for the air to go "around" the condenser at highway speeds ..You want ALL the air that goes through the grille to pass through the condenser & then on through the radiator ...I cut rubber strips from an inner tube to seal these areas ...( Look at a late model behind the grille for ideas..)  I find this VERY often on street rods....

I too have trouble getting below 40 or so degrees using R-134....I used to be able to get mid 30's on a properly installed R-12 system ...Those days are gone ... :cry:


Just some ideas .........

Bob.......

[Learpilot]

Thanks for the info about the temp control, I will try that. Right now I have it turned to the coolest stop. That sounds like my problem. I was thinking that if the evaprator was freezing tha I would feel a decrease in air flow which I am not.
I have never heard of putting heat from a light bulb on the drier, but it makes sence. I did vaccuum in down  for an hour before I put freon in.
I agree about R-12, I love that stuff. I still fly to Mexico and they have r-12 on the shelf and I would love to buy some, but the Customs guy at Brownsville, TX said the first time they would take it from me and the next time I would go to jail. That was enought warning for me.  I did change from r-134 to freeze 12 and it did lower the head pressure, not as low as r-12 but 175 psi is better than 200. The gauges read 175 psi high and 35 psi on low at 85 degrees with a squirl fan in front of the radiator.
I have a Walker Condencer and Radiator with there supplied sealing strips going all the way fron the top to the bottom of the radiator. I don't have any across the top or bottom.
I don't think my compressor is slipping, good wrap and not bottoming out.
THANKS AGAIN !!!
Rick






Just some ideas .........

Bob....... [/quote]

[Learpilot]

I did a road test this morning. At first the same thing it would cool down and then the temp would start to rise. The next run I turned down the thermostat down until the compressor clutch opened then turned it back just a little and that did it !!! The compressor will cycle and It will now cool down and stay at 50 degrees.
That will be $.50 for turning the knob and $500.00 for knowing which knob and how far.
THANKS AGAIN !!!
Rick

[UGLY OLDS]

Happy to help....You got it resolved ..Thats the important part ..... :b-d:





Bob.....

[UGLY OLDS]

I have never heard of putting heat from a light bulb on the drier, but it makes sence. I did vaccuum in down  for an hour before I put freon in.
Rick

It's an old mechanics trick to save dryers Rick.... The only reason to "evacuate" an A/C system is to remove air/moisture/last weeks compressor parts/etc from the system.
An A/C system is a "fixed size" ..That is, the system only has soo much "internal room" in the hoses/compressor/evaporator/dryer & condenser for freon. Freon & lubricating oil are the ONLY things you want swishing around in there. Anything else takes up space where freon belongs ..  

 Here's where the light bulb comes in .....
Almost all of the moisture is trapped by the desicant in the dryer or accumulator ..(Hence the name "Dryer" ,clever huh??) ...

Water boils at 212*F, ( give or take a little for our friends in Colorado & other high places) ...  BUT....When you put water under a vacuum it boils at a much lower temp.

When it's 80* Degrees out side & you suck the system down with a vacuum pump, the moisture in the system will boil ,(turn into a gas or vapor) , at 28.92" of vacuum & get removed by the pump...  NOW ...

Hang a 150 watt droplight bulb on the dryer & get it nice & toasty ..Say 158* ( VERY easy to do ..Ever touch one of those %^&^ bulbs??) ..

At 158* water boils at 20.72" of vacuum ...MUCH less work for the vacuum pump to do & LOTS more moisture is removed from the system allowing more room for the correct amount of freon to do its thing ..

The minute amount of moisture remaining in the system will get caught by the dryer ...The freon will do its thing switching from liquid to gas ...The people in the car are being cool & all is well with the world  :!:  :!:

 That's my story & I'm stickin' too it      


Bob.......

[reborn55]

Bob--very good explanaition--why don't you explain that to the ones that drive these ambulances down here.  100 degrees out--cooling 48-60 front and rear and it is not cold enough.  Get it cool--open that big old box and presto--all the a/c is gone.