Vintage Air Question

roger1 · Jun 23, 2017

ChuckG said:
I cannot answer your questions, as I no longer have the equipment here.
I simply used the duct probe thermometer over the top of the case. I might add that the water temp was 200*, and the compressor is mounted closely above the intake manifold, and close to the thermostat housing and upper radiator hose.
The ambient temp under the hood is pretty hot.

Without getting those answers, I don't think it would be good to try to make judgments on whether you need to add more oil or not.

ChuckG · Jun 23, 2017

roger1 said:
Without getting those answers, I don't think it would be good to try to make judgments on whether you need to add more oil or not.

Thank you for your help and your input.

I'm going to drive it for awhile, and see how things work.

The compressor on the car is "old". Not sure of its' vintage, but it's probably 15 or more years old, and I'm also sure it's had no maintenance in the time frame.

I'm going to keep an eye on the duct temp... and also an eye on the compressor temp.

If I was smart...

I would have taken the external temperature of the alternator...which is mounted directly opposite of the AC compressor on the driver's side.

Would be interesting to know that number to compare.

Next time I fire it up... I'll do that and report back.

In the meantime... cross your fingers.

Rick_L · Jun 23, 2017

I don't think the alternator temperature will have any relationship to the compressor temperature. The alternator makes lots of its own heat - it's inherently less efficient than the a/c compressor. It has no oil to cool it, but does have airflow from its own fan. So it's just a different animal.

You reported two different duct temperatures - 41F and 45F. Were they under different conditions? I'd be pretty happy with 41F.

ChuckG · Jun 23, 2017

Rick_L said:
I don't think the alternator temperature will have any relationship to the compressor temperature. The alternator makes lots of its own heat - it's inherently less efficient than the a/c compressor. It has no oil to cool it, but does have airflow from its own fan. So it's just a different animal.

You reported two different duct temperatures - 41F and 45F. Were they under different conditions? I'd be pretty happy with 41F.

It was ~ 41*.....42* on day #1 when we charged it up.

Day #2 (today) was much hotter.... and the duct temp was ~44*. I used the same thermometer both times.

I mentioned the alternator simply because it is in the same "conditions" as the AC compressor.... the same environment.

I guess the real question is how much does the ambient engine bay temperature effect the external compressor temperature? I was just curious...

On both days, I had frost on the inlet to the evaporator core.

My buddy Paul thinks we should add more R134... as we were running in the 15--20 PSI range on the LO side. He felt more comfortable at 25 PSI, but we didn't add any more... We decided to take a wait and see attitude.

Rick_L · Jun 23, 2017

Frost usually indicates low charge. You want condensation but not frost.

I forget the exact temperature/pressure relationship of 134, but 15-20 psi seems low to me (too cold, hence the frost). More refrigerant but not too much will bring up the pressure. Temperature and pressure is marked right on the gauge.

ChuckG · Jun 24, 2017

Rick_L said:
Frost usually indicates low charge. You want condensation but not frost.

I forget the exact temperature/pressure relationship of 134, but 15-20 psi seems low to me (too cold, hence the frost). More refrigerant but not too much will bring up the pressure. Temperature and pressure is marked right on the gauge.

Did not know that frost indicated a low charge. We felt that the pressure was a tad low too, but since the duct temps were in the 41*---42* range, we felt that was OK.

IIRC, my gauge runs from 20 PSI to 55 PSI in the "green" range.... then it turns RED----WARNING above 55 PSI ..... too high....

We added 2 cans.... 24 oz to a completely empty system...

IIRC, a full 32 oz... or 2 lbs is optimum, so another 8 oz... or 1/2 lb could probably be added.

I'm going to give it a week or so, and check it again with my gauge.

Thank you for your help.

Rick_L · Jun 24, 2017

I think I've seen 28 oz. as the capacity for a VA system.

Slightly low on pressure/temperature doesn't relate directly to lower duct temps. If the evaporator fins have frost, that reduces their ability to cool the air, even if the internal refrigerant temp is cold. Hope that makes sense.

ChuckG · Jun 24, 2017

Rick_L said:
I think I've seen 28 oz. as the capacity for a VA system.

Slightly low on pressure/temperature doesn't relate directly to lower duct temps. If the evaporator fins have frost, that reduces their ability to cool the air, even if the internal refrigerant temp is cold. Hope that makes sense.

Yes, makes perfect sense. When I mentioned frost.... it was on the inlet tube...from the dryer... That tube goes through the firewall.... to the evaporator.

I did not check the evaporator directly, so I cannot comment on the presence/absence of frost on the evaporator itself.

I also have learned that the addition of just a few oz of freon has a great effect. So... If I put in 24.... and you have heard 28....

I still have "room" for a few more oz. if necessary.

I do not want to overcharge this system. Did it ONCE about a year or so ago, and ruptured a coolant hose.

IIRC, I was running 40-50 PSI on the low side when that happened.

Rick_L · Jun 24, 2017

If you see frost on a line outside the evaporator, you can be sure that it's that way ON the evaporator.

You're right, 2-4 oz. can make a big difference - either way. Just pay attention to the gauges and the duct temp.

wagzilla · Jun 24, 2017

hotrodg726 said:
get that compressor temp. it is important for the life of the compressor.

If it 90 degree's out side and the charge is right, I almost never see the compressor over 140 degree's if the compressor is under a 100 degree's you have to much oil and you have a good chance of slugging it, if its over the 140 degree's I going to add 1/2 oz oil,and watch the temp drops.

James

wagzilla · Jun 24, 2017

I just worked on a 33 willy's a few weeks ago doing the a/c and that was fun

James

roger1 · Jun 24, 2017

Do you still have the old dryer? If so, I suggest you cut it open and meaure any oil you find in it. It may not have been able to come out when you turned it upside down.
If it didn't have any in it, then you shouldn't need to add more oil to your system.

Don't bother measuring the temperature of the alternator. It would mean absolutely nothing.

More suspect would be the accuracy of what you are using to measure the temperature. I don't trust the infrared laser guns from Harbor Freight much at all. I would guess better brands would be more accurate but still no where near as accurate as a DMM with a temperature probe.

If you system does call for 28oz of refrigerant, you need to put 4 more in. You will need a scale to weigh what you are putting in so you don't add too much.

We still need to know your low and high pressures and the temperatures of the compressor case and the input and output tubes of the condenser. Without that, continued guessing of what your issues are is not very worthwhile.

Working on A/C does require the purchase of some basic tools. Without those, it's very hard to get good results without just plain luck.

hotrodg726 · Jun 24, 2017

with your compressor temp I would add 2 Oz oil and then work on the charge. that compressor is hot.

ChuckG · Jun 24, 2017

roger1 said:
Do you still have the old dryer? If so, I suggest you cut it open and meaure any oil you find in it. It may not have been able to come out when you turned it upside down.
If it didn't have any in it, then you shouldn't need to add more oil to your system.

Don't bother measuring the temperature of the alternator. It would mean absolutely nothing.

More suspect would be the accuracy of what you are using to measure the temperature. I don't trust the infrared laser guns from Harbor Freight much at all. I would guess better brands would be more accurate but still no where near as accurate as a DMM with a temperature probe.

If you system does call for 28oz of refrigerant, you need to put 4 more in. You will need a scale to weigh what you are putting in so you don't add too much.

We still need to know your low and high pressures and the temperatures of the compressor case and the input and output tubes of the condenser. Without that, continued guessing of what your issues are is not very worthwhile.

Working on A/C does require the purchase of some basic tools. Without those, it's very hard to get good results without just plain luck.

I threw away the old dryer. Had it upside down on the bench for days, and not a drop of oil came out.

I did add 2 oz. of PAG oil to the compressor directly as was recommended with a dryer change.

I was using my air duct thermometer to measure the compressor temperature. Like this one. Has a one inch dial... tough to read.

I do not have access to a digital multimeter temp gauge, nor do I own a IR gun. I certainly can buy them.

I can borrow the professional style gauges from my buddy Paul again, if needed.

I also have no way to measure the weight of the R134. As you know, it comes in 12 oz cans...

I just might decide to take it to a shop, now that it's up and running, and is not leaking... at least not yet.

I won't have time to fool with the car today...as we're leaving for St. Petersburg and Tropicana Field to see the Orioles/Rays baseball game. I will check the temps again tomorrow.

Thank you for your help. :tu

ChuckG · Jun 24, 2017

hotrodg726 said:
with your compressor temp I would add 2 Oz oil and then work on the charge. that compressor is hot.

Yes, I agree.

roger1 · Jun 24, 2017

An air duct thermometer won't work at all for measuring the temperature of the compressor case.
So, we don't have any idea at this point whether your compressor is hot or too cold or just right at this point.

Likewise, we don't know if you have too much oil, too little or just right. Do not add any at this point.

The only thing we know is that you are probably 4oz too low on R134a.

ChuckG · Jun 24, 2017

roger1 said:
An air duct thermometer won't work at all for measuring the temperature of the compressor case.
So, we don't have any idea at this point whether your compressor is hot or too cold or just right at this point.

Likewise, we don't know if you have too much oil, too little or just right. Do not add any at this point.

The only thing we know is that you are probably 4oz too low on R134a.

Unfortunately, that about sums it up, Roger.

roger1 · Jun 24, 2017

ChuckG said:
Unfortunately, that about sums it up, Roger.

Chuck, don't take this as demeaning in any way but this is a situation where you either have to be willing to acquire some essential tools or take the car to a pro A/C technician.

We are trying to help but need better data to be able to.

ChuckG · Jun 24, 2017

roger1 said:
Chuck, don't take this as demeaning in any way but this is a situation where you either have to be willing to acquire some essential tools or take the car to a pro A/C technician.

We are trying to help but need better data to be able to.

Not demeaning at all.

I started this thread by stating that I'm an above average shade tree mechanic who knows NOTHING about air conditioning. I've restored cars frame off, rebuilt motors and transmissions, installed convertible tops and done many other things... , but AC is not in my repertoire

I think my best bet, now that it's up and running, is to contact one of the local shops that was recommended to me by several guys in my cruisers club.

I asked several guys....all excellent mechanics.... and none of them mess with AC.

That tells me something. I have a sharp learning curve.

I appreciate all of the help and advice I've gotten here.

roger1 · Jun 24, 2017

ChuckG said:
Not demeaning at all.
I started this thread by stating that I'm an above average shade tree mechanic who knows NOTHING about air conditioning. I've restored cars frame off, rebuilt motors and transmissions, installed convertible tops and done many other things... , but AC is not in my repertoire
I think my best bet, now that it's up and running, is to contact one of the local shops that was recommended to me by several guys in my cruisers club.
I asked several guys....all excellent mechanics.... and none of them mess with AC. That tells me something. I have a sharp learning curve.
I appreciate all of the help and advice I've gotten here.

I think that's exactly right.
However, since the bottom line is the cooling performance in the passenger compartment you do have the option of doing the one thing you know you can do and that's add 4oz more refrigerant. All you need to buy is a scale to measure the weight of the can while you are adding. Harbor Freight has a cheap one that will do the job close enough.

https://www.harborfreight.com/1000-gram-digital-scale-60332.html

If you did that and you are satisfied with the cooling performance, then I would suggest getting something like this to check the compressor temperature:

https://www.harborfreight.com/non-contact-pocket-thermometer-93983.html

There's obviously a lot better stuff out there than these but should get you in the ballpark. (It would be better to spend the money on a DMM with a probe like the one I gave you the link to earlier though.)

If the performance and compressor case temperature are both good, you could decide to just run it and not worry.

Like has been said, if the compressor runs over 140, it needs oil. You can do that with one of those injectors.
If it's too cool as James says, you have too much oil and some should be removed or could slug the compressor. Probably best to let an A/C tech do that though. You would have no way to recapture the refrigerant in order to do it yourself. You would lose it all and have to start from scratch.

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