Automotive Air Conditioning Information Forum (Archives)

1Funryd on Mon July 26, 2010 9:42 PM

Year: 1988
Make: Honda
Model: Prelude
Engine Size: 2.3
Refrigerant Type: R-134
Ambient Temp: 88
Country of Origin: United States

Ok I did a motor swap and had to do an AC conversion. Thanks to the help of three members on here it was successful.
Now I have new problem.

When I am driving the compressor will kick on and cool for about 15 sec(it varies), then it stops for about 3-4 minues and it gets hot in the cabin.

We successfully rewired the two relays that came factory with the Prelude, and wired it down to 1 relay, and it was working for about 3 months.

I converted to R134 and replaced the evaporator core, drier, o-rings, and hoses.
Vaccumed system and it held, we pressurized the system with air, no leaks.

When we recharged the system the pressure gauges would go up and down with the rpm above 2000rpm. This lead my ac guy to suspect that the clutch was not getting 12v.

He recommended that I put a relay between the compressor and the OEM harness so that there would be a steady 12v supply. I will be doing this tonight.

My question is, why would the compressor cool for a short period of time then shut off and then come back on again in about 3-4 minutes and start over again?

He has instructed me to bypass the OEM AC Thermostat switch, to see if the compressor will come on and stay on, if it does he suspects the AC Thermostat switch is the problem, if it does not work, then the problem is something else but do not know where to go from here.

I thank you in advance for your help.

Sean

mk378 on Mon July 26, 2010 10:17 PM

Measure if voltage is reaching the compressor when it is not cooling (but should be). If you have 12 volts, clutch should pull in-- it is probably the clutch gap. If not it could be the thermal switch. I think on that setup the condenser fan will NOT run if the thermal switch is open. So if compressor and fans are both off check the controls inside the car.

1Funryd on Tue July 27, 2010 1:11 AM

Quote
Originally posted by: mk378
Measure if voltage is reaching the compressor when it is not cooling (but should be). If you have 12 volts, clutch should pull in-- it is probably the clutch gap. If not it could be the thermal switch. I think on that setup the condenser fan will NOT run if the thermal switch is open. So if compressor and fans are both off check the controls inside the car.

Ok, I did not check voltage at the compressor, because I did the easier test, which was to jump the thermal switch behind the glove box, which eliminated the thermal switch entirely.

And the compressor kicked in and kept running. I took it for a test drive and it cooled and continued to cool, but it was not as cold as I was expecting it to be. Today reached 89-90 degrees outside.
I am wondering if there is a compressor issue now that we got the compressor to run continously and it did not get very cold.

So I now know the thermal switch is definitely one of the issues. I ordered a new one and for the time being, I bypassed the switch and let it run since its so hot. I will turn off the button should it be too cold in the earlier part of the day.

I am definitely not a fan of the R-134, it does not cool at idle only when the car gets moving. When we did the conversion, we put ES-12a(Envirosafe)refrigerant, and man, that is cold stuff. I might go back to that if we eliminate that the entire system is working and it still only cools like it did today.

For those of you who have experience with the R134 stuff, what temperature is the cabin supposed to reach with it running on a 88-90 degree day?

1stbscout on Tue July 27, 2010 10:35 AM

Being new to the board what I have to say may be somewhat suspect to some. But... I have been working on refrigeration systems since the mid 60's. My experience with the newer refrigerants has been spotty at best until I started paying more attention to the details that most, including me, forget. R12, 22 and 502 are and were very effective they made it easy to service systems and made it easy to be "lazy" about some of the details. With the newer refrigerants and the advent of "green" and the average customers desire to be both cooled and reduce costs it has become twice as important to pay attention.
Most systems that were designed for earlier refrigerants are marginally effective if converted to 134a and the rest of the system is not upgraded as well. It usually manifests itself in the cooling at low speeds and idle. Proper charge can be difficult to figure out and often the sight glass is still cloudy when the system is performing at it's best.
Due to the higher pressures at the same ambient temperatures there is more heat to be removed in the condenser in order to maximize system potential. If there are cooling issues at the condenser the system will not perform well under max load, which is usually at low engine and vehicle speed.
Now with all that said......... I have been able to attain low 40 degree duct temps on conversions to 134a. It has not been easy to figure out each system but after returning to the "design" aspects of each system and correcting the weak points in each it is possible. In the end the single most important thing to cope with is the proper charge for 134a in a system that has been either "redesigned" or simply converted. On several vehicles it has taken me over an hour to get the charge correct. With each success it is easier to know where to start and how much to start with.
Most of the conversions I do are older vehicles 60s and 70s. They are some of the hardest when the customer is concerned with "originality". On "new" conversions I always start with charging the system with about 1/2 the amount the system would hold if using R12. I then install a thermometer on the outlet of the condenser, outlet of the evaporator and in a vent in the interior. From there I add 1 ounce at a time until the system has reached a good "balance" between subcooling (assuming it can be attained), superheat, and duct temp. On some systems 1 ounce too much or too little can cut the cooling by 5 to 10 degrees. On most IF the condenser can cool the liquid to within 10 degrees of ambient and the superheat is around 12 degrees the duct temps will be at least 50 degrees below ambient. For most areas of the country this equates to low 40 degree duct temps. Here in Texas when it is 100 degrees + often the best you can do is low 50 degree duct temps.
If you want maximum cooling from any system you will need to redesign the system for the refrigerant you are using. With 134a it is critical to have as efficient a condenser as possible. If you can get condenser outlet temps to ambient or below I assure you the system will freeze you out of the vehicle.

Edited: Tue July 27, 2010 at 10:37 AM by 1stbscout

mk378 on Tue July 27, 2010 10:54 AM

Could still be a clutch gap issue. Drive for about 10 minutes with the A/C on to warm everything up then release the button and press it again to make sure it re-engages. With the switch bypassed you can get freezing of the evaporator, that's what the switch is there for. If that happens release the button and let it defrost. You're pretty much on your own with the HC refrigerant.

bohica2xo on Tue July 27, 2010 11:35 AM

Or, you could just keep an R12 vehicle full of R12. Problem solved. Especially if you are concerned with "originality".

Hondas do not convert well. A new, higher capacity condensor is needed. Given the labor & parts costs, frustration, etc. - it is more cost effective to keep the vehicle R12.

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

1stbscout on Tue July 27, 2010 12:27 PM

I know what you mean with the Honda's. Many of them had substandard cooling with R12 and converting them has just caused more issues.

The inherent problems with many original r12 installations be they factory or not are many times sufficient to be marginal when the heat is at 100 and humidity is over 60%.
I do not push my customers to convert. I don't like to work that hard

Most of my customers like to enjoy there vehicles and at the same time be able to go to shows and have them look original even if they are not. As R12 has increased in cost, and "global warming" has become more mainstream (whether or not I believe it is caused by R12) the pressure from the customers to convert AND have effective cooling is increasing.

1Funryd on Tue July 27, 2010 9:31 PM

Quote
Originally posted by: mk378
Could still be a clutch gap issue. Drive for about 10 minutes with the A/C on to warm everything up then release the button and press it again to make sure it re-engages. With the switch bypassed you can get freezing of the evaporator, that's what the switch is there for. If that happens release the button and let it defrost. You're pretty much on your own with the HC refrigerant.

Well one thing is for sure, the evaporator core is not freezing at all with the R134, and even with the thermal switch bypassed the pressure switch is kicking the compressor off due to rising pressure in the system.

I guess I am going back to either R12 or Envirosafe ES-12a.

I have discovered though that the thermal switch is an issue, and ordered another one.

I will post up my results after this week of re-converting back to another refrigerant.

1stbscout on Tue July 27, 2010 10:44 PM

If the high pressure cut off is activating you either still have the R12 switch installed or you are overcharged.

1Funryd on Wed July 28, 2010 1:26 AM

Quote
Originally posted by: 1stbscout
If the high pressure cut off is activating you either still have the R12 switch installed or you are overcharged.

You called it, I did not ever take out the R12 pressure switch. I was not aware that it would be necessary for the conversion. My AC guy might have missed that since I overwhelmed him with a H23A(92-96 Prelude) motor in and B20a5(88-91 Prelude) chassis and trying to make the H23A AC wiring and compressor work with the B20a5 OEM wiring, condensor etc.

I will bring this up to him and see what he has to say, just for the record he has been doing AC systems for over 35+ years.

We are trying to trace down one thing at a time since this is not your ordinary AC Conversion.

When doing this conversion, I was more concerned about making most of the OEM stuff work with the 92-96 Prelude motor(H23A). So originality was not what I was going for, it is more for function over form.
I am the first to get this working for this swap and I am working out all the bugs so that this swap is complete.

I appreciate everyones posts and ideas, I am learning more about AC system than I ever knew, and I really appreciate the different perspectives.

mk378 on Wed July 28, 2010 9:20 AM

High pressure cutout pressure is the same for either, it is intended only to keep from blowing the hose so it should trip around 450 psi. If you really are hitting 450 that is way too high, assuming the fans work, must be overcharged with refrigerant or oil or contaminated with air.

98audiA4 on Wed July 28, 2010 10:04 AM

not that this will help very much but i had a 92 civic that had r12 originally and when i converted it i flushed it and filled to 80% r134a. it worked perfect with the one exception: the evap switch. I ended up wiring a switch in parallel to it that I could flip on when i needed "extra" cooling. the switch would keep vent temps at 50 degrees spot on. I tried additional switches and they did the same thing.

Gordon Shumway on Wed July 28, 2010 10:13 PM

1stbscout is absolutely correct!
That is the ONLY way that you can get the correct amount of R134a (or other) into any system. period.
After you do that, then you can wish for colder refrigerant.

Every system must have the exact amount of oil for the corresponding amount of refrigerant used. Less can starve the compressor; more will hinder the atomization and condensation of the refrigerant which hinders cooling. (that's the reason for oil injectors= to adjust for the amount of refrigerant used)

1funryd.
This forum does not want any mention of alternate refrigerants, although according to the EPA website they are legal in 32 states.

Not trying to be a smart aleck, just stating the facts.

Edited: Wed July 28, 2010 at 10:29 PM by Gordon Shumway

ACProf on Wed July 28, 2010 10:29 PM

OK, Mr. Shumway,
put some facts and links where your mouth is,
please enlighten us all where the EPA has legal published information (not rhetoric from some HC blog sites) that its legal in 32 states to use HC in auto A/C systems. Exactly which states would this be?
I'd like to read for myself.

If you'd like, start a new HC topic with the specific EPA published information link.



Edited: Wed July 28, 2010 at 10:33 PM by ACProf

Gordon Shumway on Wed July 28, 2010 10:45 PM

Please bear in mind that according to the EPA there is a difference in the EPA rules regarding replacing R12 auto airconditiong with HC refrigerants, and replacing R134a auto airconditioning systems with HC refrigerants.

These rules are regularly confused without careful reading. That is the reason that the EPA has gone to extended lengths to define a "sham conversion" and a true R134a system. If it weren't important they would not have devoted such extensive paper to the explanation.

(This is similar to the "barrier hose" misunderstanding. Barrier hoses are only required on systems using R22 and blends of R22.)

Admittedly, the entire EPA site is not user friendly for trying to find information.
Please note that this webpage is specifically directed at R12 systems and their conversions.
http://www.epa.gov/Ozone/snap/refrigerants/hc-12a.html

The EPA states:

8. "The following 18 states ban the use of flammable refrigerants such as HC-12a? and DURACOOL 12a? in motor vehicle air conditioning, regardless of the original refrigerant: Arkansas, Arizona, Connecticut, Florida, Idaho, Indiana, Iowa, Kansas, Louisiana, Maryland, North Dakota, Oklahoma, Texas, Utah, Virginia, Wisconsin, Washington, and the District of Columbia."

Obviously if HCs were totally nationally illegal by the EPA, their statment would be superfluous, wouldn't it?

I further note that the EPA does not "approve" anything, they only "accept" what is submitted. The EPA is only concerned with the "environmental protection", and therefore the EPA makes no judgement as to the cooling performance of any refrigerant.

Navigating your way around the EPA site, you will discover that there are several accepted alternate refrigerants for R134a systems..... some of which are listed as ILlegal for use in R12 systems.

Why should it matter?
An interesting conundrum wouldn't you agree.

Thank you for your kind indulgence.
GS


Edited: Wed July 28, 2010 at 11:05 PM by Gordon Shumway

ACProf on Wed July 28, 2010 11:01 PM

STILL waiting for you to back up YOUR statement regarding HC refrigerants in auto AC systems,

"although according to the EPA website they are legal in 32 states."

bohica2xo on Wed July 28, 2010 11:11 PM

AC Prof:

He can't. All you are doing is giving the troll a reason to post his nonsense.

I predict the appearance of Baron Von Trollwhack shortly...

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

ACProf on Wed July 28, 2010 11:51 PM

Bo.

Perhaps.

I was giving Mr. Shumway an opportunity to back up his misconscrewed rhetoric with some bonafide actual EPA published information. He failed.

As with most trolls, they obscure the facts with puffs of smoke and use the magicians art of redirection.

As quoted from the early computer game Adventure, a prelude to Dungeons and Dragons....."FOO! You're nothing but a Charlatan".

So long, Mr. Shumway!

Edited: Wed July 28, 2010 at 11:56 PM by ACProf

bohica2xo on Thu July 29, 2010 12:13 AM

Prof:

It is always the same straw man arguments. It gets old after a while.

BTW, that name is telling all by itself. Google it.

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

Gordon Shumway on Thu July 29, 2010 12:39 AM

You know. It kind of pisses me off that my posts are disappearing.

Don't you feel special.

TRB on Thu July 29, 2010 12:54 AM

Quote
Originally posted by: Gordon Shumway
You know. It kind of pisses me off that my posts are disappearing.



Don't you feel special.

Why do you not address the unique fitting issue required by all SNAP accepted refrigerants. So the only way you can make your claim is by doing a sham conversion which is not allowed.

I have not deleted a post today. But I'm not toe only one which has the rights to sweep up the floor and empty the trash.

PS: I thought you said you would never mention this crap again a few days ago?

-------------------------
When considering your next auto A/C purchase, please consider the site that supports you: ACkits.com
Contact: ACKits.com

ice-n-tropics on Thu July 29, 2010 12:28 PM

Hi 1st,
Your objective testing approach to R-12 conversion to R-134a is recognized for application of the scientific method to determine your 3 primary variables. Some of your results may be a little different from mine in Texas, but your basics are certainly on the right track.
I've measured sub-cooling (SC) and superheat on over 12 conversions during charge optimization measurements with results within a range of 85% to 92.5% of the original R-12 spec charge amount. This was always at over 90 ambient, usually 95 to 100 degrees. Sin City was 115 Tue: that will adjust thinking on condenser subcooling because SC decreases the condenser surface area for latent heat-X as pressure discharge skyrockets. Less subcooling (less 100% liquid in the bottom of the condenser) is better above 100 deg., for Pd and vent temp.
A condenser that would dissipate enough heat to attain a outlet temp only 10 degrees above ambient at Texas severe ambients has not been my experience. Don't know how to do that!
Also, I have found that while the R/D is filling with liquid, that the charge amount is forgiving and the Sh and Sc doesn't change until the R/D and liquid line are liquid. Of course, when the R/D and liquid line fills with liquid and liquid begins to fill the lower cond channels, then Pd and Td rise dramatically as SC increases (while Pd is increasing).
Above a ambient threshold, about 95 deg (depending on the particular PAG chemistry), the sight glass with PAG goes ballistic with milky foam as the PAG becomes insoluble with R-134a. With POE this is not the case, and the sight glass method is still as useful as with R-12. Volvo is the only OEM (other than 2 cyl CCI/York) with POE retrofit.
As for upgraded A/C systems (FMCO and GM) on 60-80 MY, the micro tube multi pass condenser upgrade is dubious at best. Idle performance is sometimes worse after "upgrading/?" a old fashioned tube and fin with microtube. I think this is because the scientific principal of small internal tubes is that the velocity is higher and the turbulance is higher, thus increaqsing heat-X factors. At idle the turbulance is lower and increased pressure drop becomes a negative.
Keep sharing your useful comments,
hotrodac

-------------------------
Isentropic Efficiency=Ratio of Theoretical Compression Energy/Actual Energy.
AMAZON.com: How To Air Condition Your Hot Rod

Edited: Thu July 29, 2010 at 12:32 PM by ice-n-tropics

1stbscout on Thu July 29, 2010 8:43 PM

Hi Ice,
I have fought hard and long to get some systems to work at 10 degrees above ambient for SC. Then again at times I can be a bit extreme... going as far as flushing the old tube and fin then running "Aluminum wheel cleaner" through it both inside and out. I am after as much contact as I can gain.

I just finished a 1972 GTO conversion that is running at 110 degree outlet temp with shop temps in the 106 degree range (humidity in the 90 to 100 range as it rained on and off all day). Agreed I spent hours cleaning and setting up this system before I charged it. But most of my customers don't ask how much it costs they ask how well does it cool

On systems were the customer does not care so much about original I will "stack" condensers and add electric fans. The original condenser is plumbed to a second one in front of it then to the R/D. With this setup I have been able to get outlet temps at ambient and the system cools really well.

The idea came from 2 places. First was due to experience with very large commercial air units. Second was due to a 1938 Chevy where the customer wanted a/c that worked like a new vehicle and obviously space was at a premium. For that one I ended up stacking 3 cores in reducing size forward of the radiator.

I too have noticed the sight glass foaming as the proper charge is neared. First time I was at a complete loss. It was nearly perfectly clear then 1 ounce more and poof it was cloudy. That first one I spend nearly a week recovering and flushing etc. bound and determined I was going to have a clear sight glass. LOL Finally I just did my normal and charged until I got the best balance.
Anyhow..... Hope y'all are staying cool and don't mind if I "chime in" from time to time.

1Funryd on Fri July 30, 2010 12:23 AM

I was thinking of adding a 7" thin fan on the front of my condensor to help cool the condensor more.

It seems to work well for another Prelude owner friend of mine, but he is running an OEM system and has replaced the condensor and all parts with R134 compaitble components.

So his setup is different then mine, but still same chassis, just different compressor.

Here is my setup:




If you notice we had to add more piping to the OEM fittings due to the shortness of the original piping when I purchase the used compressor.






He installed a fan in front of the condensor and is able to keep very cool at idle. Here is his Prelude below:





And all his new components:

mk378 on Fri July 30, 2010 8:08 AM

Does your car have the same condenser as was shown with the white car? That rather large serpentine condenser should work pretty well with 134a.

Cooling the condenser more never hurts. Try the water mist test and if the pressure drops a lot, the fan should help. Also if the only problem is inadequate fans, you'll still get good cooling on the highway. If that doesn't describe your situation, your system is probably overcharged or too much oil.