My AC burns me up --- Summary of fix

[Discseven]

Originally Posted by crownarch

Karl, 3 in 1 makes a electric motor oil specifically for this purpose and it is dirt cheap and works fantastic. Your motor will be whisper quiet if you do this.

Can that be found at ACE hardware Gary? Or are we talking electrical motor shop? TY for input. (Feels like another round trip into plenum is on horizon.)

[rick-l]

Originally Posted by Discseven

Can that be found at ACE hardware Gary?

If you live in Maldives it is.
3-In-One Electric Motor Oil Hand Tools, Sewing Machines, Fans Bottle 3 Oz - Ace Hardware & Home Centre, Maldives

[Discseven]

TY Rick. Remote... but will go.

[wwest]

In the factory position with a properly calibrated T-stat the compressor will cycle off at 26+/-2dF... Obviously the inlet area will be colder, think old style steam heat radiator.

In the center position and with extra capilary tubing exposed to cold airflow the compressor will cycle off before the outflow area declines to ~26dF.

But, forget all of that, the bottom line is with the T-stat in the full CW position it MUST cycle the compressor off at a high enough AVERAGE temperature that the evaporator doesn't freeze up.

That's why it seems a bit foolish to me to target the lowest vent temperatures for proper refrigerant fill levels. You might even get to -10dF, but you then have to limit the COLD level to 33dF on the average using the T-stat setting to prevent freeze up.

Oftentimes owners try to get colder vent temperatures by pulling a larger and larger portion of the capilary tube out of the evaporator core... only to later find they have reached the freeze up zone, or beyond.

[wwest]

Originally Posted by Discseven

I hear you... but... Fact that t-switch may not be calibrated to spec based on position of probe is not a problem from my perspective. What is sought here is for t-switch to modulate compressor with increasing ON duration the further CW the switch is turned. If it does this to some acceptable degree... I would consider switch functional.

But not so much that some portion, inlet area most likely, of the evaporator operates on the average below 32dF...

We could extrapolate difference t-switch probe function by considering temp difference in evap from the core (where I have probe) to outside edge near inlet where "stock" probe position is. Am going to guess that temp difference over those few inches is not so great that switch is going to work drastically different. Perhaps I'm wrong. Once 26 oz is reloaded and switch is checked, IF there's cause... probe can be moved.

For added detail here Will, with probe positioned in evap's core, is compressor likely to cut OFF sooner or later as compared to probe near inlet?

Sooner.

[Discseven]

Originally Posted by wwest

Sooner.

TY for comments Will.

Goal was to bring system to near optimal meaning it would operate near its freeze threshold here in Miami---ambient moisture taken into consideration. Given an earlier test comparing temp in outlet of AC blower to vent with +1 dF delta at vent, and core temp test with temp dropping below 32 (albeit with no blower positioned), and driving v-temp at 32+ dF (speed 2 at around 85 outside ambient)... seems safe to say evap is operating at near optimal now.

Once upon a time I had noisy AC that blew near cabin temp air. Improvement is understatement. Perfect not necessary. My toying further with system is for fine tweaks and better understanding.

Will system hold 32+ dF at vent when ambient is 95 dF during mid summer? Will system now be able to flush car of internal heat reasonably fast after car's been parked in direct sun for 30 scorching minutes? We'll see when next summer comes.

Speaking of summer, subject of Targa roof insulation was raised. Don't recall where discussion went on that---insulated...or not(?) With extra roof on hand, am planning to take it apart to find out (and rebuild it.) From what I know, there's exterior skin, then burlap, then metal, then headliner. Seems there's better insulate than burlap to use. Be good for Targa roof expert to chime in.

[Ronnie's.930]

Originally Posted by wwest

That's why it seems a bit foolish to me to target the lowest vent temperatures for proper refrigerant fill levels. You might even get to -10dF, but you then have to limit the COLD level to 33dF on the average using the T-stat setting to prevent freeze up.

How many 911 a/c systems have you been able to charge to -10dF using the method you are disparaging above? The coldest I have been able to get with that technique is a vent temp of 26dF (measured after a drive in mid 80s ambient), and 29dF measured at idle in 98 ambient (pressures on the low end of acceptable ranges). This is with a 3 condenser system, albeit with a 1/2 bay tail condenser.

And right, the vent temperature & pressure charge method is "a bit foolish" - only a fool would want cold blowing a/c that quickly clears cabin heat and enables conditions where the compressor is not required to run all of the time to maintain an extremely comfortable interior environment, right?

[wwest]

Of all the people that doesn't understand.....

[wwest]

Originally Posted by Discseven

TY for comments Will.

Goal was to bring system to near optimal meaning it would operate near its freeze threshold here in Miami---ambient moisture taken into consideration. Given an earlier test comparing temp in outlet of AC blower to vent with +1 dF delta at vent, and core temp test with temp dropping below 32 (albeit with no blower positioned), and driving v-temp at 32+ dF (speed 2 at around 85 outside ambient)... seems safe to say evap is operating at near optimal now.

Once upon a time I had noisy AC that blew near cabin temp air. Improvement is understatement. Perfect not necessary. My toying further with system is for fine tweaks and better understanding.

Will system hold 32+ dF at vent when ambient is 95 dF during mid summer? Will system now be able to flush car of internal heat reasonably fast after car's been parked in direct sun for 30 scorching minutes? We'll see when next summer comes.


Speaking of summer, subject of Targa roof insulation was raised. Don't recall where discussion went on that---insulated...or not(?) With extra roof on hand, am planning to take it apart to find out (and rebuild it.) From what I know, there's exterior skin, then burlap, then metal, then headliner. Seems there's better insulate than burlap to use. Be good for Targa roof expert to chime in.

It seems to be common knowledge that the first thing to suspect is wrong in the case of evaporator freeze up is, would be. low refrigerant charge, I don't have much of an idea how that might be but will post my theory below(***). Perhaps CG can chime in and explain why that is using his "book of knowledge".

But it seems to me that focussing on vent temps as the major target leaves one fully open to the possibility, probability, of a low refrigerant charge. For myself, having not the knowlegde to be exact, I would shoot for the lowest vent temperatures but with a limit of suction side pressure indicating P&T temps above freezing. Plus a high enough engine RPM in order to ascertain that at FULL load and perfromance the low side suction would remain in the "safe", non-freezing range.

Up to now I Have always relied on the inexpensive kit gauge for topping off systems. But now that I have a gauge set I think the next time I will shoot for the greatest Delta "T", intaking outside airflow, windows open, and with elevated engine RPM.

I suspect that procedure will put me in the exact same charge "ballpark" as using the low side gauge reading as the charge level target... awaiting the next HOT day.... next June?

*** MY theory...With low refirgerant charge, and/or engine RPM so low that "apparent" charge is low, the core area near the inlet gets plenty of cooling, while the mid to end points on the core doesn't sode the evaporative process is limited to the narrow area near the inlet.

Meanwhile the system is working as hard as it might therefore the inlet area quickly drops below freezing, freezes up, and now that freeze "front" slowly progresses across the core until all airflow is blocked.

[wwest]

Originally Posted by Ronnie's.930

How many 911 a/c systems have you been able to charge to -10dF using the method you are disparaging above? The coldest I have been able to get with that technique is a vent temp of 26dF (measured after a drive in mid 80s ambient), and 29dF measured at idle in 98 ambient (pressures on the low end of acceptable ranges). This is with a 3 condenser system, albeit with a 1/2 bay tail condenser.

And right, the vent temperature & pressure charge method is "a bit foolish" - only a fool would want cold blowing a/c that quickly clears cabin heat and enables conditions where the compressor is not required to run all of the time to maintain an extremely comfortable interior environment, right?

I fully admit that I am having a very hard time grasping the idea of getting vent outflow temperatures well below freezing, 26dF, for more than a quick cabin cooldown period or with Rh extremely low.

I'm even having trouble with the stated T-stat setrpoint range/span, 26+/-2dF open, 33+/-2dF close. With a "square" hysterisis the average would be below freezing, but one must assume a non-square hysterisis functionality, longer period to go to "close" vs getting to "open".

The hot and humid climates that exist in my area of direct knowledge, Memphis, etc, would not allow for that.

[wwest]

Originally Posted by Discseven

TY for comments Will.

Goal was to bring system to near optimal meaning it would operate near its freeze threshold here in Miami---ambient moisture taken into consideration. Given an earlier test comparing temp in outlet of AC blower to vent with +1 dF delta at vent, and core temp test with temp dropping below 32 (albeit with no blower positioned), and driving v-temp at 32+ dF (speed 2 at around 85 outside ambient)... seems safe to say evap is operating at near optimal now.

Yes, excellent job on your part, EXCELLENT!

But "evap....at/near" But what about the SYSTEM at/near. I am of the belief that the compressor you "upgraded" to has less pumping capacity vs RPM than the factory original. What happens when you raise the engine RPM, the supply of liquid refrigerant to the TXV rises accordingly?

Once upon a time I had noisy AC that blew near cabin temp air. Improvement is understatement. Perfect not necessary. My toying further with system is for fine tweaks and better understanding.

Insofar as preventing freeze-up, "perfect" is necessary.

Will system hold 32+ dF at vent when ambient is 95 dF during mid summer? Will system now be able to flush car of internal heat reasonably fast after car's been parked in direct sun for 30 scorching minutes? We'll see when next summer comes.

Speaking of summer, subject of Targa roof insulation was raised. Don't recall where discussion went on that---insulated...or not(?) With extra roof on hand, am planning to take it apart to find out (and rebuild it.) From what I know, there's exterior skin, then burlap, then metal, then headliner. Seems there's better insulate than burlap to use. Be good for Targa roof expert to chime in.

I'm in Boise, 37.8dF this AM, with the '78 at the moment, I'll check the top and egt back to you.

[Ronnie's.930]

Originally Posted by wwest

Of all the people that doesn't understand.....

Exactly - YOU do not understand and do not want to understand (since understanding would involve a loss of face on your part); yet despite your lack of knowledge and experience with automotive a/c, you strangely keep posting as if you are an authority on the subject. You might want to reconsider who should be the recipient of the rolly-eyes that you are so fond of.

* Sorry Karl, but I can't sit back quietly and let West call what I do "foolish" when my results say otherwise and he is not qualified to lob a/c criticism my way in the first place.

[wildthing]

I shouldn't have thrown out that old popcorn bag. Thought this was over.

[Discseven]

Your v-temps lead pack Ron. Nothing for you to prove AT ALL! (Until I beat it Come summer mofo... I'm back in saddle gunning for 009'rs arctictemp.)

You and Will... going off deep end again. Put brakes on that sh** pls. Healthy discussion where we all can learn something... f'in great!...

Lov ya but no F'in arguing. (Wayne'll shut this sh** down again if we can't control ourselves.)

[Ronnie's.930]

Originally Posted by Discseven

Your v-temps lead pack Ron. Nothing for you to prove AT ALL! (Until I beat it Come summer mofo... I'm back in saddle gunning for 009'rs arctictemp.)

Thanks, and good point, Karl - letting my results speak for themselves is a better approach. And good luck with the artictemp-duplication quest, bub - come and gettcha sum!!!

[LM3929]

Very nice write up, I hope to use most of it this winter.

Do you have a list of the O rings needed or their sizes?

Thanks Lorne M.

[Discseven]

Originally Posted by LM3929

Very nice write up, I hope to use most of it this winter.

Do you have a list of the O rings needed or their sizes?

Thanks Lorne M.

TY Lorne. Here's my system's o-ring reference. Unfortunately, I don't know sizes other than calling them "hi," "low," and "equalization" fitting o-rings. Might be standard sizes but don't quote me on that. If CG (Kuehl) picks up on this post... he can say for sure. Also... I did not disconnect any of my 3 condensers so do not know config of those connections---another CG question.

High & Low connections at evaporator...




Equalization connected to low side plumbing exiting evap.




High & Low connections at compressor. (O-rings not in place in this photo.)




Depending on your receiver / drier... 2 high line o-rings. I got Kuehl R/D where o-rings were included. (Adaptors were also included so one size Kuehl R/D fits all.)




Kick azz on your AC project!

[GH85Carrera]

Originally Posted by LM3929

Very nice write up, I hope to use most of it this winter.

Do you have a list of the O rings needed or their sizes?

Thanks Lorne M.

If you go to any supply shop for automotive AC they will sell you a bag of green o-rings for AC for a few bucks. It will have seals you don't need but it will have a lifetime supply of o-rings for most home hobby AC guys. I suspect even the local FLAPS has them.

And be sure to always put a few drops of the oil for the AC system on each o-ring before you put it together. And try hard to not over-tighten the connection. Just a good snug fit is enough. It is real easy to get a gorilla grip on it and over tighten it and smash the o-ring into bits. Don't ask how I know that.

[wwest]

Nostalgic AC - AC O-Rings - Fittings & Hose Kits

[Omegablueray]

I wish I had it in me to overhaul my AC system. I guess i'll just have to fork out the cash to get it better than new someday.