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Cycling at higher than normal vent temp? Pages: 12

somedude01 on Mon April 09, 2012 12:29 PM User is offline

Year: 1990
Make: Honda
Model: Civic Si
Engine Size: 1.6L
Refrigerant Type: R-12
Ambient Temp: 85
Pressure Low: n/a
Pressure High: n/a
Country of Origin: United States

First off, i'm sorry to say that I don't have pressures at the moment. I posted last fall about a Civic that I had trouble with cooling even though I retrofitted with a parallel flow condenser. I got sick of it and bought some R12 to use. I have a Civic Si with the matsushita compressor, AMA parallel flow condenser and whole new system except the thermostat. The system was charged to a clear sightglass at 1500rpm and cools decently. My compressor cycles off at 52f vent and comes back on at 56f vent temperature. Doesn't matter if moving or parked, it cycles at those temps no matter what.

My questions are: Is that a little high for cutoff? Shouldn't it be around 40f off and 45f on? Should I replace my thermostat in that case? Should I come back with pressure readings when it is cycling?

Cussboy on Mon April 09, 2012 2:26 PM User is offline

Did you add the amount of R-12 that the hood sticker states to add?

You really also need to supply both low and high pressures, with compressor on, at about 2000 rpm.

mk378 on Mon April 09, 2012 2:53 PM User is offline

Make sure there is no reheating from the heater core, as the air leaving the evaporator may actually be colder. If it's not that, then yes the thermostat is out of whack.

somedude01 on Mon April 09, 2012 4:29 PM User is offline

I didn't charge by weight because it's now a custom system with the Parallel flow installed. I also need to wait until it gets hot again to check the pressures to make sure they're around 85f when I did my last vent temp check. Also, I did not think of the reheating. I will check that on my next drive. Thanks for the suggestions, everyone.

mk378 on Mon April 09, 2012 7:34 PM User is offline

Civics often have a problem with the water valve on the firewall not closing fully with the dial on the dash turned all the way to cold. This can usually be solved by adjusting the cable at the valve.

Edited: Mon April 09, 2012 at 7:36 PM by mk378

James89dx on Wed April 18, 2012 4:21 PM User is offline

So you went with a parallel flow condenser? I've looked at that off and on in my quest to get adequate A/C in my '89 DX hatchback. What size did you go with and what did you do about the fittings?

somedude01 on Fri April 20, 2012 9:25 PM User is offline

So I manually shut off the heater valve in the engine bay and to my surprise, it actually had an effect. The system cycles off at 48f and comes back on at 54. These temperatures are at idle on an 88-90f day in the sun with the car closed up on Recirc. Not a a large difference, but noticeable. I'm gonna try clamping off the heater valve soon to see if there's a difference. I have no pressures yet because school has been hectic and I haven't been able to get my gauges back from my friend yet.

As for the parallel flow, you can use all of the stock lines if you have a Matsushita compressor. I'm not sure for a sanden, but all I did was just bend the living crap out of them. I believe it's a #10 and #8? o-ring fitting for inlet and outlet. I don't think the inlet had to be bent at all because the pflow's inlet was in the same exact location. The outlet had to have the living crap bent out of it because the original was angled upward and the Pflow was to the side. I used the 12x23 condenser from AMA. Any taller and you'll have to sandwich it against the radiator. Any longer and you have to get ALOT more creative with line bending/cutting/shortening. Using this height and length condenser allowed me to just bend the lines to where they hook up. If you decide to bend lines, bend them around something round. If you don't, the lines will crease and they'll be ruined.

R-134a was alright with my Pflow, but the R12 changeover is what got my A/C to 52f at idle on a 90f day. I also sealed off the condenser on all sides to the radiator. This made the biggest difference in idle temp. My A/C would go up to 64f at a stop before I sealed the condenser to the radiator. My condenser fan shroud is also bent and not sitting flush against the radiator... Does anyone have any experience with the fans on the AMA site? I'd love to get a high power puller to replace my stock condenser fan. I believe my A/C would get even colder.

James89dx on Sat April 21, 2012 1:42 PM User is offline

Very cool! Looking at your pictures, I'm wondering if you might have had the room for the 12x27 without too much extra bending. Would your condenser slide an inch or so toward the passenger side or is that as far as it'd go? I have the Sanden TR70 in my DX.

Here's my setup:

I see we both have the line going straight across the front. I had to bend mine a bit to fit the condenser pusher fan in there.

It looks like my line here I would just need to bend straight:

How did you "seal" the condenser to the radiator? Is that the foam I see sandwiched between the condenser and radiator? I don't even have the stock fans in my car. I just have an electric puller for the radiator fan and an electric pusher for the condenser. I'm guessing pullers are far more efficient when they have shrouds covering entirely the back of the radiator to sort of create a vacuum type effect. I assume this is why stock fans always have shrouds. Even without a shroud though my puller radiator fan works fantastic.

Here's mine:

I know pullers are more efficient, but I guess logically it doesn't make sense to me that having a high performance pusher directly on the condenser wouldn't help. I guess I was never able to confirm this because my system never worked quite proper to test.

Out of curiosity - did you add more oil to the system than the stock requirement? And any idea on how much total charge it took?

Hate to semi-jack your thread but it's nice to find another EF owner who's into getting a nice working A/C system. Hardly any of the ricers on the Honda sites even care about A/C they all strip them out for mAd hPz y0

somedude01 on Sat April 21, 2012 6:22 PM User is offline

I frequent honda-tech alot and I've seen your threads regarding A/C. If I were you, I would get 2 puller fans and then seal off the condenser to the radiator so the puller fans are literally forced to draw air through the condenser at idle. My 91 DX would creep up to 75f at idle because it was missing all of the condenser seals even though I had 2 pullers.

I used this:

The carpet foam hanging down from the bottom is because I had bulk carpet padding left over from my new carpet so I sealed off the bottom of the condenser with it. My vent temps at idle went from 64f to 54-56f after JUST the condenser seal.
My car, like yours, would be ice cold and cycle while driving and behave normally until I stopped. Condenser seals fixed that.

Manually shutting off my heater valve was also worth 4-6 degrees with A/C on. I went for a drive with all A/C and fans off and temp knob set to cold and it turns out my heater would burn you even if it was all the way set to cold after just a 10 minute drive! Reaching into the center vent and touching it, of course.

Just make sure to seal the condenser off on all sides to the radiator with the foam stuff. What also helps is resealing the vents by taking the dash out and using the foam seal strip stuff. And buying a new evaporator if it isn't new already. Having a new evaporator and sealing vents gave me alot of vent strength and flow. I think that helped my a/c alot.

Edited: Sat April 21, 2012 at 6:23 PM by somedude01

James89dx on Sat April 21, 2012 8:37 PM User is offline

I had another Hayden fan leftover from a previous project and decided to see if I could make it fit on the front of the condenser today. It wouldn't fit with the stock t-bar but I just cut it out, welded in some new steel bar moved over a bit and reinforced it on the top and bottom and was able to get both fans on the front of the condenser. I hooked them up to the battery and they blow hard, right through the radiator even. I can put my hand behind the radiator and feel a good deal of air flow. I know pullers are more efficient but I just can't see how this shouldn't be effective.

When I get it my new thermostat and pressure switch in from Honda and get it all back together I'd be interested to see how the two pushers work. If they don't work very well I'll have to go to a puller and build a custom shroud on the back or something.

I sealed all my vents with new foam strips a few years ago with my first go-around at this. I'll probably pull the dash again and check it to see how it's all holding up. I am putting in a new evaporator (again) this time. I'm also pondering fabbing in a stronger blower motor because the EF one is pretty paltry. I appreciate all your input.

I forgot to check my heater valve today. I'll have to remember to check that.

somedude01 on Sun April 22, 2012 1:22 AM User is offline

If you still have good vent strength I wouldn't bother pulling the dash. I only resealed my vents because ironically my heater wouldn't heat the driverside vent in the winter time. Keep me updated on those fans. I want to see whether they help or not. Also, is your car tinted? And do you use an electric pump to vacuum with? Whenever my dad redid our GMC's with a venturi pump the A/C would suck bad in hotter weather.

I would be surprised if those 2 fans in unison failed to keep your idle temps down. If all else fails, order that parallel flow from AMA. Get something round and invent some new cuss words while bending the receiver lines. Keep me updated as well, I'm curious as to how this works out.

And about the parallel flow fitment, it can't slide any further to the passenger side. The unibody is in the way. And placing it exactly where it is makes it so I don't have to bend the condenser inlet line. If I had the 27 inch wide condenser I would have to get real creative with line bending.

As for oil, I added exactly 5 ounces of BVA auto 100 glow from AMA. 5 ounces is what the Matsushita system calls for. I drained the shipping oil from the compressor and spun it slowly while putting the BVA oil in. I then spread out the oil between the rest of the components. Reused hoses were flushed with brakleen non flammable/non residue brake cleaner to isolate the oil quantity variable. The system has a new evaporator, compressor, condenser, expansion valve, reciever drier, and dual pressure switch. I used nylog on all of my fittings and o-rings, and black light tests after 6 months reveal no leaks. I will use nylog for every A/C job from now on, this makes me a believer!

And can anybody chime in with experience on how much of a difference insulating the low side lines makes (if any)? This Civic has a long low side line and it's stuck in that hot engine compartment... I'm always looking for ways to make this A/C colder.

James89dx on Sun April 29, 2012 9:49 PM User is offline

Did you insulate the low-side line and, if so, did it make a difference?

This weekend I fitted a blower motor/fan assembly from the late '90s GM trucks into my stock blower box housing. My brother had an EF Civic years ago and tinkered with this idea himself and found the GM assembly to be a decent match to the EF (plus, being a PepBoys manager he had the luxury having access to many different makes of fan motor assemblies and found this to be a decent physical fit). The motor is much more powerful and the fan itself is also a bit taller.

Here is the GM assembly. I pulled the vent tube off of the Civic assembly and it fits right into the hole on the GM fan motor (thankfully):

Here is the GM assembly sitting into the Civic box:

As you can see it "bottomed out" on the inner shroud (also notice the stock Civic vent tube all fits up nicely):

So I cut the shroud out some:

I then created an "adapter" out of two different MDF plates that allowed me to use the stock Civic locations and screws. And boy, this took forever and was quite frustrating but I got it eventually. As you can see the GM motor grounds to the fan assembly itself, and so I just used a ring terminal at one of the mounting screws. To get the fan motor to mount at the stock Civic locations, I only had to slightly modify the edge of the GM assembly a little bit on two places. Mounting the GM fan motor this way, I don't have to hack up the stock airbox should I want to go back to stock later on or have problems with this one. The only thing I would need to do is source that inner metal shroud.

Then, playing around with the fresh air vent, I realized it didn't secure quite close all the way shut. I'm sure this is how all those leaves keep getting in my blower box (and then onto my evaporator). Thinking about it, I realized I have only ever used the fresh air vent a handful of times in any of my cars. So, I removed the flapper assembly, cut out of piece of ABS plastic to fit the vent opening, and plastic welded it in place to seal off the blower box. Also, the EF Civic has a manual driver side fresh air vent too should I ever want use it (though I know I won't). I haven't yet, but I plan to put some sort of filter on the blower box intake section. This will ensure I won't get crap down into my evaporator and also work as a sort of shade-tree cabin air filter. I may fab something that is removable/replaceable.

I spent most of the day today at my brother's PepBoys store trying to figure out how to get this wired up with the factory climate control and for all the speeds to work properly. This was a major hassle - wiring it straight-up to the factory harness the fan blew on full-power anytime the ignition was ON, and the climate control had no bearing on it - the factory wiring also got REALLY hot REALLY quickly and was quite worrying. He then suggested I use a relay. The stock Honda system uses no relay setup, just the resistor for 1, 2, and 3 speeds while 4 bypasses the resistor for full power. We wired in a relay setup and initially could not get the high speed (4) to work. 1, 2, and 3 would work but nothing on 4. Finally, my brother figured out how to wire it all after studying the factory schematics (he's way better at that stuff than me), and so now all 4 speed settings work through the factory climate control unit.

We used a general Bosch style relay and put an in-line fuse between the relay and battery, and we believe (hope) the setup is all on the up-and-up. My brother actually pulled the wiring schematic for the newest Civics and lo-and-behold the system is wired EXACTLY how we have this one wired. In fact, they have identical blower box/fan speed wiring to the EF except with a relay added in like we did.

Anyway, after all of this - the A/C blows HARD. You can actually FEEL the air now coming from the driver and passenger vents, and the center vents blow hard all the way into the backseat. I drove around for nearly an hour tonight on the highest speed setting to see how it all reacted. The factory blower female harness (with the blue/black and blue/white wires) as well as the wiring several inches back gets pretty warm to the touch, as does the relay. I know the relay is pretty normal but I don't know if the stock setup gets warm at the harness?

It's not warm enough that I think it would melt or cause any damage, but I'm just not sure if it does that stock. I'll have to keep an eye on it or maybe check to see if anybody on HT knows for sure.

My new evaporator thermostat and pressure switch will be in Tuesday from Honda, so I'm hoping to get this all going by next weekend.

Edited: Sun April 29, 2012 at 9:54 PM by James89dx

somedude01 on Sun April 29, 2012 10:36 PM User is offline

I haven't gotten to insulating my low side line yet. I was hoping someone else knew if it made a good difference or not. One way to find out!

I never would've guessed in a million years on how to put that stronger blower in the car. I'd settle on just learning how to wire the relay in! Just remember you might not get really low vent temperatures with such a strong blower in the car now.

Now that school is over and the weather is heating up I will try to clamp off my heater lines to see if it makes a difference in the vent temperature. I also have my gauges back from my friend so I can finally get a reading on how my R12 system is doing. I will post back with my results. I really hope I don't need a new thermostat for this thing!

Thanks for the update also. Lemme know how it goes when the A/C is all together!

James89dx on Sun May 06, 2012 1:59 PM User is offline

Why do you say I won't get low vent temps with the harder blowing fan? I think I read that somewhere before (may have been one of your posts actually) but I'm not sure I understand why fan speed could/would affect temp.

Anyway, I put the system all together today, and will be charging it this afternoon. I'd like to hope this time it'll all work fantastic but I'm not getting my hopes up, I've been let down several times before lol.

somedude01 on Sun May 06, 2012 3:48 PM User is offline

I don't have the know-how to tell you why, I just know that it does. Inversely, my vent temperature drops with the lower I set my blower fan. You'll still get cool vent temps, just a few degrees warmer from all of the airflow.

Also, clamping off the heater lines made no difference to my Civic cycling off at 48f. They are still manually adjusted all the way closed, though. I will put the gauges on and get the reading of my Civic's system when I'm done with my friend's car.

Speaking of my friend's car, I just charged the A/C on his Sunfire and it got down to 42f vents all closed up at an idle on a 90f day. That Sunfire's system makes me jealous honestly.

James89dx on Sun May 06, 2012 8:05 PM User is offline

Well, I got it all done. For the longest time I couldn't get the compressor to engage and was thinking oh great here we go again, and I even jumped the pressure switch and tested the relays and all that crap before realizing I forgot to plug that harness into the evaporator thermostat. When I realized that I was mad at myself for overlooking that but relieved it was a "simple" fix. After that charging went smooth.

A few pics (and forgive me for jacking your thread with my stuff).

Vacuuming it down - I vacuumed it for an hour and a half then verified it held vacuum for two hours

Here's my final condenser fan setup. I didn't want to put those plastic ties through my condenser so I ended up welding on several tabs to hold the fans in place. Between the tabs and the custom T-bar the fans stay in very tight. I ran both fans off the same circuit. I'm not sure if that reduces the effectiveness of each one but they seem to work great.

Here is my vent temp while driving, I'm very pleased!

Once I came back home I sat in the driveway and let it idle for about 15 minutes just to see what the highest temp it would climb up to and this is about as hot as it gets (right about 50)

I'm really loving these vent temps! Granted, it was "only" 90 degrees during these tests but so far so good. The true test will be when it gets up into the higher 90s and whether or not I can go out for lunch at work in my office attire without my shirt sweating to my back lol.

These vent temps were with my GM blower fan on full blast. I forgot to test it on lower speeds but if they get a few degrees colder than these temps then even better!

I did also put some fat foam insulation strips between the radiator and condenser. I know it wouldn't matter much with my pusher fans but I decided to go ahead and do it now so that if I need to switch to a puller fan setup for better performance I won't need to pull my condenser/radiator again.

And lastly, man, on my little 1.5 liter it is very very noticeable when the compressor is on. It suddenly feels like I'm carrying several passengers in terms of reduction in power lol

Edited: Sun May 06, 2012 at 8:11 PM by James89dx

somedude01 on Sun May 06, 2012 10:57 PM User is offline

Those are some awesome results! Is that with R12 and the regular serpentine condenser? I definitely think I have a thermostat problem now when my parallel flow and R12 don't even go that low! Mine doesn't go lower than 48f vent even when cruising in the rain.

Even my Si notices the A/C drag a little bit. Not as much as my auto DX did, though. Just make sure your idle boost works. Before I replaced my alternator and did my ground kit addon, my a/c would bring my idle down to 500rpm and it would bog like hell 24/7. Now my idle is like 900ish with A/C on with much less drag.

And don't worry about replying in here. It's great to have all of this 4th generation Civic info all in one place. The A/C on this generation can and will work well with R12 and proper condenser airflow/capacity. I always thought my A/C would never work, honestly!

James89dx on Mon May 07, 2012 12:13 AM User is offline

Yeah, R12 and stock (new) serpentine condenser. I put in a new thermostat and pressure switch and I'm so glad I did even though it set me back a couple weeks waiting on it and $140 bucks.

So your compressor cycles on at 52 degrees and off at 48 degrees? My gauge isn't marked precise enough to get that specific but mine seems to have a much wider range. Yours seems to have a pretty tight "window" whereas mine seems to be about 10 degrees "window".

I've always had problems with idle speed on this car it'll dip down to what appears to be about 400 RPM sometimes and adjusting it doesn't do much. I think though the gauge is a little off. I have a CRX dash in it and 90-91 gauge cluster/hood and I think the tach is somewhat inaccurate because it'll sometimes show about 100 RPM at idle but I know it can't be THAT low.

Thankfully, my car seemed to idle right at about 1K RPM today with the AC on, but it doesn't bog down pretty noticeably for a split second when the compressor is first engaged.

James89dx on Fri June 08, 2012 12:40 PM User is offline

Just want to update this now that it's been getting hotter. Back in May the highs were "only" in the low 90's and nowadays it's been getting into the high 90's. Some observations:

On a hot day, if I've had the car sitting in the sun all day, then hours later starting it up (like, say, leaving work at 5 PM when it's been sitting in the parking lot all day), the car has a hard time getting under about 60 degrees idle vent temp. So, unlike my other cars, I can't start the car and sit at idle to let the AC cool down, because it won't ever work its way down any cooler than about 60. But, once I start on my way home, it will cool down to about 50 at the center vent rather quickly - within a couple of minutes. If I get stuck at an intersection within these first few minutes after leaving work, the center vent temp will again creep up to about 60 at idle.

After about 7-8 minutes of driving the center vent temp gets right down to about 42 while driving and, after this point, even at red lights, the center vent temp will creep up to 50 but won't go higher. About 10 minutes in of my drive it'll get down right to 40 while driving and stay right between 40-45 the whole time, and at intersections creep up to 50.

My lone disappointment so far was a week or two ago I got stuck in a drive-through for a solid 10-15 minutes, so I was idling the whole time. It was about 97 outside and granted I was in the direct sun but my AC vent temp eventually climbed up to 60 and sat there. I was JUST on the verge of sweating. I thought about revving the engine up to get the compressor turning faster but decided I'd rather not look like an idiot sitting in the drive through revving randomly.

somedude01 on Wed June 13, 2012 10:58 AM User is offline

I'm afraid to report back with the same exact results you have. If I do rev the engine while stopped it will drop the vent temp a good 4-6 degrees but it still wont really cool below 60 unless i've cruised for a while already. I have not fixed my one weak condenser fan, however. I'm going to see if I can convince a doctor to get me a medical exemption for windshield tint and put clear ceramic tint on the windshield in an effort to help. I hear Florida allows exemptions like that for windshield tint.

I want to also add that my blower motor seized up on me 2 weeks ago, and although the service manual says you have to discharge a/c and remove everything to get to it, if you unbolt both boxes and get violent you can wiggle the motor out. I was not about to lose my expensive R12!

My car also cools ice cold after I start to cruise. My vent temperatures almost immediately drop to 50 the second I get above 40mph. This makes me wanna put dual spal pullers or some aftermarket fan set on my car to see how it cools. I still need to hook the gauges up to my car and see how the system is doing and how it reacts to a light condenser mist. I'm hoping these cars are able to cool well in some way or another at idle.

I'm also a lifeguard so I just jump in the pool before I leave for the day to counter my so-so a/c. This technique sometimes leaves me regretting my decision because the a/c works twice as well if you're soaked.

I've said this but when I get enough time I'll report back with vent temps and pressures. I will also include a before and after misting when I do.

James89dx on Thu May 23, 2013 1:38 PM User is offline

Any updates on your system? I'm happy to report a year later no changes in my a/c system (I guess no news is good news in that sense).

I do still wish my idle vent temps could be lowered but I haven't messed with it any further.

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