I have a 1990 Civic Wagon that I'm trying to get the AC working properly.

I charged the system up and was monitoring pressures at idle and at 2000-2500 rpm.

I'm used to a system working where if the low side pressure drops to a certain amount the compressor kicks off and allows pressure to build so it works properly. This one does not seem to do that, and the only switch is this dual pressure switch that resides on the high side line.

So when I get it up higher than 2500 rpm my low side pressure is down to around 5-8 psi. At idle it'll be around 40psi.

Is this normal behavior for the Honda AC in these cars?

Just wondering if I'm missing something here as I'm not getting all that terribly cold of an AC, vacuum tested it, it held vacuum.

Evacuated the system, replaced the expansion valve and dryer, reoiled the compressor and recharged. Just hoping I'm missing something obvious here.

 

How much oil did you add to the system?

New or old compressor?

 

How much oil did you add to the system?

New or old compressor?

 

New compressor. Used nearly an 8 oz can of oil, have a touch left in it, so 7ish.

 

If you have nearly 8 oz of oil in it you've got way too much oil. It only takes about 4 oz of oil.

Also, you didn't state whether or not this is r12 or r134a? If the latter good luck getting it to ever cool adequately. These cars do epically terrible with r134a.

I went through the time and expense of reverting back to r12 and I would still only describe the system as barely adequate for Texas weather.

 

It's R134a

So 4oz in the system completely. The FSM states 4oz if you're replacing the compressor. That doesn't take into account oil in the other parts of the system. I did start off with only half that amount and the compressor was noisy. Adding more quieted it down. Maybe I should have given it more time to fully circulate as I was adding? Either way I can always take some out and give it another go.

My question is still unanswered. Does the low side normally drop down to near nothing? On all other AC systems I've dealt with there was a low side pressure switch that cut off the flow at a certain PSI and let it build back up to cycle. There's no low side pressure switch in this system, just a dual switch on the high side. Does anyone have a reading of what their pressure is on the low side at 2000 rpm?

 

what is your high side pressure? low side pressure is only half the story.

 

40psi on the low and 170 psi on the high.

 

All right, recovered, drained, vacuumed and recharged just to make sure of everything. Now I'm getting much higher pressures. Maybe too high. Seeing 70-80 on the low and 290 on the high. If I let it sit and idle it'll creep up to the shut off on the high side and cycle off.

Is that as intended?

That is at idle, which I'm missing my exhaust heat shield, and it looks like my thermostat might be stuck open so my main fan never kicks on. At least if I'm driving now though the AC is much colder than before. It doesn't cycle off if I am moving. I suspect that's back to the fan issue.

 

If I'm reading correctly, it sounds like you're implying that it is your belief the A/C compressor should never cycle off? Why do you think that?

I don't at all remember my pressures (and mine would likely differ from yours a bit since I'm R12), but my compressor definitely cycles at both idle and while driving, as do all of my cars.

Unfortunately you won't get too much A/C help here. I've been there done that. Keep in mind, a lot of the guys here purposely ditch their A/C systems!

A few years ago when I was trying to get my A/C going, and there not being much help on Honda-specific sites, I ended up finding autoacforum.com - ton of knowledgeable people and posts there. I would strongly suggest giving up hope of getting much help here and checking that site out.

 

I don't think that. I know it should cycle, what I'm saying is I've just never experienced a system where it only cycled based on a high side pressure switch. No low side switch throws me.

So I'm not sure what readings are good for low and high side psi. The fsm just tells me volumes, so what I'm used to seeing in my truck and other cars are not the readings I'm seeing here.

Just hoping to get it as cold as I can without blowing out the compressor. I'll check out that other site. I'm probably pissing people off not trying to properly stance my car or done such nonsense

 

We need more information on ambient temperatures and what your pressures are at idle and 2500 rpm.

270 for the high side is higher than I'd like a system to be. I believe you need to double check your fans and be sure that the sides of your condenser are sealed to the radiator so no airflow is permitted to pass around the condenser at an idle. Also be sure that your fins are not obstructed with debris. The low side should ideally be around 30-35. But, once again, this all depends on ambient temperature.

The systems you're familiar with are "Clutch cycling orifice tube" systems. They have a low pressure cutoff and cycle when they get cold (low low-side pressure). Our ED Civics use "Thermal expansion valves" and have temperature cutoff sensors on the evaporators, and usually only shutoff if the evaporator gets cold enough to freeze, or your high pressure is out of control.

Do you have one fan or two fans?

James89dx and I have been on quite the hunt for a long time regarding these ED A/C systems and the consensus is that they suck. I've now settled with a parallel flow condenser swap with R-134a and the system still sucks in 92f FL weather for at least 10 minutes until the car cools. I even have my entire car including the whole windshield done with metallic tint to no avail.

Edit: Your A/C switch should automatically command both fans to be ON when it is pressed. You may have other issues if both fans aren't running with A/C on.

 

I'll get those to you ASAP. Ambient has been 85-90 the last couple days. Idle the Low side was 70psi and the high was up there around 260. If I let it idle, the high side will climb all the way up and trip the high side pressure switch. Then it'll cycle off, pressure will drop back down to around 250-260 and then repeat.

I can't recall the high side at 2500 RPM but the low side would drop to around 45-50.

I do have two fans if the AC should make them both come up, definitely have a problem then as only one ever comes on for me. The seal around the shroud is pretty good I'll double check that though as it looks like I'm going to have to be checking the fan at minimum anyway. The condenser is in fair shape there are a couple ratty looking bits of fin but no major squashed down areas or anything.

Either way. I have some work to do on it, no heat shield on the exhaust, toasting up the lines and obviously the fans. I have some stuff that's wrong. So I'll work on that and get back to you guys. Thank you both for your replies, they've helped me out a good deal already.

On a side note, how did you manage to metallic tint your whole windshield and keep it legal? =D

 

Hooked the fan to the battery, it came on. So problem wasn't the fan. Checked the socket, no voltage at the socket. Checked the wires, they looked sound.

Checked the fuse.... Wasn't even a fuse in the socket. I swear I don't know what the previous owner was doing with this thing but it baffles me on a daily basis.

Both fans now work when the AC is on. I'll see if I can't get a heat shield on that exhaust and get some better readings.

On a side note, are you guys doing any extra wrap on the hard lines to try to keep them cooler? I guess there was just no other place to put them but to have them a few inches away from the exhaust, just seems very inefficient.

 

Well, certainly not my effing day. Got some measurements, popped the gauges off, and BAM valve stem leak on the high side....

Back to square one.

 

I didn't do any wrap but I did so this in an effort to get some more airflow across the condenser and help idle performance (as you can see I had to cut the factory T-bar out and fab up my own to fit the fans):







Even with all this extra work with my fans and r12 I would still only describe my cooling as barely adequate for Texas weather. Seems like idle performance just sucks no matter what. sumdewd has an impressive parallel flow setup with r134a and seems his performance is about the same as mine. My car takes a solid 5-7 minutes of continuous driving to start cooling fairly well. If I have it sitting out in the parking lot all day at work and go home for the day (or out to lunch), and get stuck at a light or heavy slow traffic during those first few minutes I'll start sweating like a pig. Contrast this with either of my two Maximas ('92 and '93) which can sit at idle and cool right down into the 40's center vent degree temp).

Seems like a lost cause on these cars unfortunately.

 

When my car does get cool, it stays cool. I turned my fans down to 1 and 2 yesterday idling in traffic in 92f weather while wearing jeans and was still getting cold. I was driving away from the sun, though.

The tint is not legal by any means. It's just light enough to not be noticed easily. (50%) Which is ridiculous--How many people am I going to kill with a 50% tinted windshield?

Even though your shrouds are sealed to the radiator, make sure your condenser is also sealed to the radiator top to bottom, left and right. Some 3-4$ packs of sticky weatherstrip from Home Depot will do this for you. This will help calm down your 70psi low side at an idle. Also be sure to check the condenser fins closely. Bugs can really get packed in there and it's hard to see.

 

I will tell you, though, that the Parallel Flow condenser helped immensely. My car would never cool at an idle with a serpentine condenser.

I used a combination of foam carpet cushion and sticky weatherstrip to seal the condenser to the radiator. If you don't do this, you'll run into a situation where the A/C will never cool while sitting still.

Fitting a parallel flow condenser into this car is possible with just bending your existing hardlines because the fitting sizes are perfectly the same.

 

Consider tinting your windows. These cars need all the help they can get with regard to A/C performance. My rear 3 windows are 15%, driver and passenger are at 25%, while the windshield is at 50%. I do feel as though the heat has been cut back by at least 50%.

You can feel the difference by holding your hand in the sunlight through the tint and rolling the window down and feeling it.

I also use one of those reflective sunshades when the car is parked. It's also a good idea to drive the first 2 minutes with the windows rolled down a little bit at the start of a drive to vent the initial heat out.

 

Yeah tinting is absolutely on the list of things to do. I'll also check that the condenser is sealed to the radiator. Had I not just recharged it again I'd probably look at doing a different condenser. At minimum I'll definitely be pulling the front off to make sure it's all clean when I do go to check that it's sealed up nicely.

Interesting fan set up DX are those pushers in addition to the stock fans as well?

 

Charged back up, had a major storm here today and temps are low so can't really do any solid tests at the moment. Gonna seal the condenser to the radiator and make sure that air flow is proper.

Hopefully this should hold up for a while though, especially after the tinting. We'll see though when it starts getting properly hot. Maybe this will just teach me to not be a sissy.