matt965

With winter approaching, this thread is kind of meaningless right now. That's exactly why I'm doing this now instead of driving with no A/C in the summer. I think most people here don't care much for A/C on these cars. However, I daily drive an EF and having A/C in south Texas is a must. I know this topic has been discussed on several threads before, and the general conclusion is that 134a in EFs just suck. Either deal with it or go with something else.

My cheapo TR70 clone decided "no more" when the clutch bearing froze. I was never too impressed with its performance anyway, so I started thinking: what if I ran a 134a compressor on an EF? I've seen this topic touched briefly on one thread, but I never saw anyone actually try it.

So off to the junk yard.
I found a 1995 DX with all original A/C components in-tact. I pulled the compressor bracket with idler pulley. The engine mount is something extra and not needed in the EF. It must be removed for the bracket to fit.

I ordered a new compressor for a 1995 civic. Comparing the 2 compressors, the hookups are identical except the 95 has tilted ports and they are spaced out a little more.
Comparing the EF bracket and the EG bracket they mount on the block using the same 4 bolts. They will bolt to the 1.5 and 1.6 blocks without issue. Just keep the bolts from the EG, they are different lengths than the EF.

All other components remained (they are 6 months old), of course I got a new dryer (now with a sight glass!). I didn't bother replacing the condensor because I wouldn't know what to look for. I also don't want to retro fit the half-size condenser on an EF at this time.

For the most part, the new compressor bolted right in, no problem. I had to bend the high line just a little for it to mount. The trick is to keep the line from touching the exhaust. The new compressor had different o-rings and the EF o-rings are not thick enough to seal. I went through my collection and found suitable o-rings. Vacuumed and charged. It holds!
Unfortunately, the pressure switch picked a bad time to fail. I went back to the engine bay wondering what all the noise was, and found the low side at 0psi. Wish it failed before dropping that compressor in...

I won't know how much of a difference this compressor will make until summer rolls around... I will post results then.
I'd like to hear input on this. What do you guys think?

4drEF

There is another thread where somebody did an R134 conversion, but used the R134 type condenser and expansion valve.
He reported great success.

rallypoint_1

https://honda-tech.com/forums/honda-...3035110/page2/

Forgot....you need to use newer barrier type hoses or the r135 will leak out in few months or so. Molecules are smaller than R12

94eg!

iTrader: (2)

I rebuilt my TR70 system (89 CRX Si) with an aftermarket Parallel flow condenser and R134a back in 2011 or 2012. It's worked great ever since (HOT Las Vegas NV) barring some electrical trouble. I didn't even replace the expansion valve either. Just the o-rings, oil, refrigerant, drier & condenser. I did drain all the hoses and evaporator and blew out the metal lines with brake cleaner & compressed air.

I flushed the compressor's mineral oil with SuperCool PAG46 a few times and used the correct oil & refrigerant volumes based on the calculations provided on Sanden's own website about R134a retrofits. I just remembered the numbers came out exactly the same as the early NSX's with R134a, so I ordered the AC service label from the dealership so I would never forget. lol

I can't tell you what brand compressor I have.....only that it was a previously used TR70 style compressor given to me by a friend (could be completely aftermarket or a remanufactured Sanden).

arries289

Interesting.....I always thought the condenser was the limiting factor on R134 conversions since it ideally requires a larger one? Because of that, I still run a factory system with Johnsons R12 Freeze refrigerant. It actually works really well except the Panasonic compressor clicks at idle. I upgraded the main fan to a higher CFM which helps cooling at idle and I will be replacing the compressor with a Sanden unit in the near future.

94eg!

iTrader: (2)

A parallel flow condenser of the same size as a the factory serpentine condenser will be much more efficient at transferring heat from the refrigerant to the air. Naturally the fit is not perfect even though it is an application specific unit.

smilindave

What is the internal difference in the compressors? I am in process of repairing my 91 crx and would like to know as I will have a/c when done with the body repairs.
Regards
Dave

GeoMetry

By application specific do you mean that it is designed to fit a 1989-1991 Civic/CRX? If so please provide the Brand and part number so I can look into that next time I have to fix my A/C.

Thanks.

GeoMetry

Is it possible that you need a different pressure switch? Does an R134a system work optimally at the same pressures as an R12 system?

94eg!

iTrader: (2)

Uh oh. Sorry but it looks like they may not be in production anymore. Probably too many returns due to fitment problems.

....and by fitment problems, I mean this:

sumdewd

Wow I didn't expect to see my thread linked considering it's so old. I'm still driving that hatch with the parallel flow conversion, though its days are numbered. The biggest issue is getting the charge correct. The A/C was never really right until I bought a scale and a refrigerant cylinder, then vacuumed and charged to EXACTLY 30.8 ounces for my system. The cans really don't cut it.

James89DX is another user on this site with a hatch in Texas who swapped a TRS090 (96-00 Civic) in, made custom hoses, and got amazing results with the ebay parallel flow condenser designed for the EF. His swap was detailed on another website and you might be able to find it if you do a little bit of googling. Not sure if it's against the rules to link to another Honda forum, though. He even mentioned he could make the custom hoses and ship them for a nominal fee, since he bought a barrier hose crimping kit or something.

I'm still using a MatsuSHITa compressor, and aside from a ticking noise from hell at idle it's working fine.

matt965

I replaced everything with brand new components, some may even be designed for 134a. I never checked this before installing...

I have that exact one. Had to cut the core support, too. It sat on a shelf for a few years, but I installed it back in early May. I found it on another website though, can't remember where... I think it may be a 134a condenser. Time to do some research!

I thought about this while at the junk yard. I pulled the switch from the 95 but the threads are too big to fit the EF line. I think draining the system would confirm if my switch is really bad...

matt965

Updates

I have replaced the original switch with a known working switch and the compressor is still not cycling at all. There is currently 6 oz. Of 134a in the system and it will run even at 0 psi on the low side. The system does blow cold however, so I suspect the wrong type of switch is being used here.

I have a couple options: retrofit the switch from the 1995 civic to my car, or get an adjustable switch.
I haven't found anything about adjustable switches for our cars, but there are reports of some stock switches being adjustable on other makes so this is something to check out.

I may end up retrofitting the replacement switch. Will update when this is done.

DaX

iTrader: (1)

Have you checked the thermo-switch that senses the temperature in the evaporator core? Mine died, and I just replaced it with a programmable switch I got on amazon. Writeup here.

matt965

Doesn't that probe just break the a.c. circuit so the compressor stops? I know its temperature based so I would think this wouldn't be doing anything when charging with the first can of Freon. It just isn't getting cold enough.

My symptom starts as soon as I begin charging the system. When it is vacuumed, the compressor does not turn on. But once the first ounce or two of Freon is added, it does turn on but won't cycle. The compressor just keeps going and going...

I can test that part, but I don't think that's it because the evaporator isn't getting cold enough for that probe to do anything.

DaX

iTrader: (1)

The dual pressure switch (under the hood) is supposed to be open (doesn't allow the compressor to run no matter what) when the high pressure side is below 33 psi, closed when it is 33-340 psi, and open again above 340 psi. What you described above makes sense - at full vacuum, your compressor should not run because it is below 33 psi. Once it gets above 33 psi, the dual pressure switch will allow the compressor to run, as long as the high pressure side of the system doesn't go above 340 psi. Think of the dual pressure switch like a safety or kill switch. It does not control cycling of the compressor, but keeps the compressor from cycling if the system is over charged or under charged. Because your compressor won't cycle when a vacuum is pulled, but will start to cycle once you begin adding refrigerant (and likely putting the high side of the system above 33 psi), this means your dual pressure switch is probably working as it should.

The thermo-switch (under the dash) is what actually cycles the compressor on and off. The switch is supposed to be open (compressor off) when the evaporator core is close to freezing (depending on the particular switch in the Civic, this is between 31-35F), and the switch is supposed to be closed (compressor on) when above 36-41F (again, depending on the particular switch). If your compressor is staying on once you start to add refrigerant, I would think you have one of two scenarios happening:

1 - You aren't adding enough refrigerant. If you don't fill the system to the recommended values, the evaporator core will never cool down to the temperature required (31-35F) to cycle the compressor off. If you have a fan, put it in front of the condenser, open the hood, and crank the car. With the AC on, dash vents only, and recirculate, use a thermometer to measure the temperature of air coming out of the center dash vents. It should be 31-35F (or close) before the compressor turns off. Are you using a set of R-134a gauges? Are you using a scale to see how much refrigerant you are putting in the system?

2 - You may truly have a bad thermo-switch that is stuck closed. This will make the compressor stay on regardless of the temperature the evaporator reaches. In this scenario, air coming out of the vents would get very cold, but eventually warm up as the evaporator freezes over. Testing for a 'stuck closed' thermo-switch is a little more difficult than the other way around unless you live somewhere cold. You need to make sure the probe is below 31F, then measure continuity across the switch - if it is closed below 31F, the switch is bad.

matt965

Is that thermo switch also what cycles the compressor when the freon is low?

DaX

iTrader: (1)

As I understand it, it is the only thing that cycles the compressor. It is in series with the dual pressure switch. I'm no AC expert, but I believe if your refrigerant is low enough to not cool the evaporator sufficiently, but not low enough to trip the dual pressure switch, your compressor will run constantly.

matt965

What you say makes sense. The AC can't get too cold or else ice will form on the evaporator. I believe the thermo switch also helps keep the low pressure in check so the compressor doesn't lose it's lubrication. When the freon is low, the evaporator can't get cold enough and thus the compressor will never shut off. I have also noticed this.
However, I think the pressure switch has a role in the cycles as well. It keeps the high pressure in check, but as you say it also opens when the pressure is not high enough. I believe this is the case when charging the system with the first few ounces of freon from a vacuumed state since the compressor is supposed to have very short cycles until it has enough pressure to keep running. Mine is not doing this and will be problematic if I develop a leak in the future. I won't know it until it's too late.

I swapped the thermo switch with a working switch and I'm still having the same problem. Here's a pic of what my gauges are reading.

DaX

iTrader: (1)

I'll repeat again that I'm no A/C expert, just a hack....three questions about the picture you posted:

1. How much refrigerant do you have in the system?
2. Is this picture taken with the compressor running?
3. hat was the ambient temperature when you took it?

In the picture of your gauges, your low side is in vacuum, and if the compressor is running, I'm pretty sure this means you don't have enough refrigerant in there. When I converted to R-134a, I put 26.0 ounces of refrigerant in the system. I charged mine when it was about 75F outside (I think), and if I remember right, my high side was reading about 175 psi...but don't quote me on that, I'd have to go back and check my notes. I believe I was told you should really be weighing how much refrigerant you put in - high side pressure is dependent on ambient temperature and how much airflow you have going across the condenser.

Based on what the manual says, I don't believe the pressure switch cycles the compressor. See attached. It says it only opens due to leakage or blockage. Again, I could be wrong, but this is how I interpreted it.

sumdewd

Do the gauges equalize when the vehicle is shut off? What is the ambient temperature? Are the gauges zeroed out? Are there only a couple of ounces in the system? Does it even try to take a full charge? How are you evacuating and recharging this system?

You're pulling a vacuum on the low side... Something is not right. It's also hard to troubleshoot when a system is not fully charged. Short cycling when charging is more common on systems that use an orifice tube instead of an expansion valve. These systems only shut off for low temperature, or high/low high side pressure. The orifice tube systems shut off (cycle) based on a low low-side pressure, or a high high-side. We need more info, but I'm kind of leaning toward a bad expansion valve (or obstruction) and a low charge.

And don't forget, it's entirely possible your clutch gap is too tight (in addition to low charge/cold ambient). It will never cycle if your clutch gap is too close. I recommend turning off the A/C and double checking that the clutch's outer hub stops spinning.

matt965

I think it's time I give some clarification. Things are getting too obscure now.

-The system is modified. Everything has been replaced with new parts. The condenser is the newer style to handle 134a and the compressor goes to a 1995 civic which is designed for 134a.
-The system holds freon and for the most part works as it should. When it is fully charged it gets cold and pressures seem normal.
-When I charged the system with the old TR-70 compressor, something made it run in short cycles until it had enough pressure to stay running. Low pressure never went under 25psi.
-I have the new compressor in, and it runs even when low side is under vacuum. It stays this way until the system is fully charged where everything works as it should. I have a problem with this because should I develop a leak I will have destroyed my compressor by the time I realize a leak exists. When there isn't enough pressure, oil isn't able to move through the lines and lubricate the compressor.

@DaX
1. Around 6 ounces right now. I know it isn't enough, I already stated this earlier.
2. Yes.
3. Not sure, I think it was around 80*
26 ounces was too much for mine. High pressure went beyond 400psi before finally tripping the switch. This was on a 100*+ day. I found mine ran good at around 19 ounces or so.

@sumdewd
Gauges equalize when system is off. Not sure, around 80* I think. Zeroed out? Around 6 ounces in the system, I already stated this in an earlier post (I'm aware it isn't enough). It does charge as it should. I vacuum the system using a vacuum pump hooked up to the gauges.
The system works as it should when fully charged, hence why I'm trying to fix this issue when it isn't fully charged. Every AC I've worked on with the expansion valve setup has always short cycled when charging with the first can of freon. This has just been my experience. This also should be happening when there is a leak and pressures get too low. This is to protect the compressor from lack of oil so it doesn't rip itself to shreds, sending metal shavings throughout the system.
If clutch gap was too tight, the compressor would be running even when I turn it off, right? I don't have that issue. Never had it at all.

sumdewd

That definitely clears things up. I'm afraid this is just an old system. There is nothing preventing this A/C unit from running at absurd low-side pressures. Your best indicator at this point is when you notice the system isn't cooling as well, which would start WAY before the low side approaches this pressure.


This was taken from page 15-47 out of the FSM.

DaX

iTrader: (1)

Now I understand what you're asking, and unfortunately, that is beyond my knowledge of AC systems.

matt965

I received a tip from a friend that solved my problem. Apparently, GM used a low pressure switch on the later r12 systems and many r134a systems that screw on the accumulator (usually). I pulled a switch from a 1993 Silverado and I installed it on the low pressure service port of the civic. I had to remove the adapter that was on the line to make it work. As for wiring, I tapped into the circuit for the high pressure switch. For my setup there are a total of 3 switches that must be closed before the compressor is allowed to run:
- temperature bulb
- high pressure switch
- low pressure switch

The switch did the trick. The compressor was very rapidly cycling on and off with the 6 ounces that was in the system. However, I had to go to O' Reilly and get an adjustable switch because the one from the chevy was turning the compressor off too soon (probably around 24 psi). For those curious, the new switch is a Murray 36674 (it's adjustable, even though it isn't specified).

It's a little cool outside now so I can't say if the new compressor will make a difference. I'll come back here once it gets hot again.