Wing Nut

Hey guys, I'm new to this forum, but I've been over at Preludezone.com for a little while now. I'm looking for a bit more technical information and experience than just opinion, I hope you guys can help.

I bought my 98 Prelude (base) last summer with the hopes of giving it some tlc to get it to where I want it (basically just clean and mechanically sound). I've done a good bit of work to it already, and now I'm at the AC.

Issue 1: the AC works great when it is below 85* or so. I don't have a thermometer yet, but with my experience it is right where it should be in temperature. However, anytime it gets over 85* or so outside the AC can't seem to keep up. It gets coldest on low, and progressively gets warmer as you turn the fan speed up (an obvious fact since it blows more warm over the evaporator fins). But it is nowhere near acceptable for the heat we have here in Florida.

Issue 2: I have also noticed that there is a faint hissing sound coming from under the glove box area when the AC is on and the rpm's are above 1000-1500 (it's not a leaking-type hiss, but more like a pressurized system hiss, if that's clear at all). I have read in some places that this is a normal sound for the expansion valve, but other places I have heard it may mean a bad expansion valve. Can anyone clear this up for me? It does not hiss at idle, but only when moving. And when it does hiss is when the AC seems to be coldest.

Issue 3: When the AC is run for more than 20 minutes or so, there seems to be an excessive amount of condensation build-up on the evaporator box inside the passenger footwell. Often it is to the extent that it drips and creates a wet spot on the carpet. I know that the drain line is not plugged, because there is a significant amount that drips underneath the car also. Any ideas?

What I have done: About two months ago I took it to a mechanic friend who has his own manifold gauges and evac machine and hooked it up. Everything seemed fine to him, though the system was a bit low on r-134a so he decided to add some (By the way, the fans work fine, the compressor engages, and all the switches and vents work properly). The system wasn't really taking any, so he revved the engine a little bit, at which point it started pulling some r-134a into the system. However, he must not have been watching the gauges carefully and apparently overfilled the system, putting a load on the engine, and making the compressor belt squeal. We immediately shut it down and evacuated the system.

He assumed that the compressor may have had some issues, but I wasn't convinced because it had been working "alright" up until then. So I took it home and added 1 can (21 oz.) of store-bought r-134a just to get me through vacation for a week (I know, it's not best, but I just wanted it to hold me over). It was cool "enough" again, but still didn't work well when stopped or over 85*.

After vacation I took it to a reputable mechanic who had some newer equipment. I told him the issues, and he evacuated the system again and said it was about 500 grams low (if I remember correctly). He added the right amount with oil (and some dye), and it was still only blowing about 68* (heat index was 110* that day) according to his thermometer.

They couldn't tell me why it wasn't as cool as it should be, so they sent me on my way.

I have read slowcivic2k's thread: https://honda-tech.com/forums/tech-misc-15/%2A%2A%2Aair-conditioning-c-guide-how-works-when-doesnt%2A%2A%2A-2900177/ and it was very helpful. I hope to take it back to my friend's place so I can get some accurate numbers for you guys, but my best guess at this point is the expansion valve?

I'm sorry for the excess information, but I'm hoping it may be helpful for someone to help me diagnose this.

Thanks,
Seth

P.S. On a side note, while on the way back from that vacation the AC would get warm even on the freeway sometimes. I would turn the AC off while leaving the fan blowing, and it would still blow cold for 3 minutes or so then it would warm up to the outside air temperature. When I turned it back on I had a couple small (pencil lead size) pieces of ice come out of the vents and it was cold again. Maybe it was icing up because it was a little low on refrigerant?

minilogoguy18

Don't ever add anything to the system, you obviously have no idea how the A/C system works and overcharging the system can increase the pressure in which the ECM will not allow the compressor to come on.

If you're mechanic friend was smart he should have raised the car on a lift and stuck a air blower into the evap drip tube to blow out the dirt that's clogging it causing the wet carpet because no matter how hard the system is working in FL it should never do that. The clog can reduce performance but only slightly.

Since you finally have UV dye in the system that can at least trace your small leak, the next thing you need to check is compressor clutch clearance. It's very likely on this old car the clutch is worn and has excessive clearance and that can definitely reduce performance. Max clearance should be 0.65mm.

Wing Nut

Aside from the condescending remarks to me and the insult to my friend, I appreciate the helpful information you gave. I know that I have much to learn about how the A/C system works, I will be the first to admit it. That is precisely why I mentioned that slowcivic2k's thread was so helpful to me, and it is also why I am asking for informed help with my issues.

I am aware that overfilling the system can cause damage and/or danger, but my friend is human just like you are, and he does make mistakes from time to time

As for the evaporator tube, I'm pretty sure it is not plugged, and that it is condensation on the case that is dripping...not overflowing. But I will check to make sure. Thanks for the insight.

And also thank you for the insight into the clutch clearance. I will research into checking/adjusting that.

Thanks for the help, but I would appreciate some general respect in our discussions here.

-Seth

Wing Nut

Can someone tell me why an excessive amount of clearance between the plate and the pulley would make the compressor less effective? How does it work?

minilogoguy18

It's a electromagnetically actuated clutch, inside the rotor there is a field coil, the rotor spins freely while the armature plate is splined to the inner shaft. The armature plate can only move so much, if there is excessive clearance it will slip causing a loss in performance.

I'm a Honda tech, especially in FL this time of year I get my fair share of A/C jobs so I'm quite experienced but no one can tell you over the internet whats wrong without looking at the car themselves. You should take it to someone with experience, HVAC isn't something that should be played with at home in the garage without the right equipment. Freon is very poisonous when inhaled and can cause pretty bad frostbite on something like your finger in seconds if sprayed with it.

The drain tube thing is super common, it will cause condensation to build on the evaporator and make the floor wet on the passenger side. I had an Element that was like that and a quick shot of compressed air into the tube from the bottom cleared it out and caused a few gallons of water to spew out onto the floor.

holmesnmanny

There was nothing condescending about his remarks. If you don't know how to handle constructive criticism you shouldn't be posting to an online messageboard.

integra15

Issue 2 is annoying but normal. The hissing sound was always present in my prelude.

Issue 3 there should not be drips of condensation, maybe some of the plastic is cracked and water is dripping out. The core is surrounded in foam and the condensation should be dripping right through the drain tube.

Wing Nut

Ok, Thanks, that helps a lot. I think I understand it better now. I eyeballed the compressor clutch clearance and it doesn't look drastically out of spec (don't quote me on that please...I understand my eyes can't see +/- .15mm), I just haven't had a chance to actually get out there and measure the specs yet. Thanks for the info minilogoguy.

Wing Nut

So you presume that part of the nature of an online message board means that anything goes? I do not want to bring up anything that would insult minilogoguy, but there is a difference between constructive criticism and helpful criticism (a seeming redundancy, but some use the term constructive criticism as a license to say whatever they please). All I am going to say is there is a difference between the two in how you say what you say. I'm not entirely sure what your point was in posting this other than to pick someone else's issue. (For anyone else reading, I'm just clarifying why I have said what I have).

Once again, thank you minilogoguy for your helpful information.



Hmm, interesting. I don't mind the sound, I just wanted to make sure it was normal. And I mean to check on the evaporator box and the drain tube. Thanks for the insight!

Wing Nut

I have finally had a chance to do some real troubleshooting on my AC. I think I have a direction to head, but I want your opinions first.

Using the chart and procedures in the Haynes manual (copied here: https://honda-tech.com/forums/showthread.php?t=2900177) I got the following information:

Outside temp: 88*
Humidity: 50%
AC air temp: 67* (while running 1500rpm on max AC, recirculate, speed setting 4)
Low side pressure: 5psi
High side pressure: 220psi

According to the chart and the given temp/humidity my low side pressure should be 40 psi, and the high side pressure should be about 250psi.

My conclusion is that the system appears to be a little low on refrigerant since both sides are lower than they should be, but the low side is far below where it should be. This leads me to believe that there is a block somewhere in the system (likely the expansion valve?) In addition, I do not think there is a problem with my condenser because on the inlet side it is very hot (leading me to think it's the expansion valve) and on the outlet side it is cool(ish).

In addition, while driving today I noticed that while cruising on the freeway the compressor would cycle after 1.5 minutes -- it stays on for 1.5-2 minutes (temp gets down to 62*) and then shuts off for about 1.5 minute (temp goes up to 80*).

It sounds to me like pressure is being built up in the system so the compressor has to shut off to allow it to equalize to a safe pressure. (Btw, turning the AC off then on with the switch does nothing to get the compressor to turn back on. I just have to wait either way).

Does this make sense? Anyone have any previous experience?

P.S. Someone told me to check the compressor clutch clearance. Technically it's a bit close at .2mm (should be .35-.65mm), but I don't think that's a problem.

Also, the evaporator drain tube is working fine. There is no sloshing around inside, there is a steady drip coming from the tube, and there is also a small stream of air blowing out of it - so it's all good.

Wing Nut

I know there are some experienced technicians on here. Can anyone help?

holmesnmanny

something isn't right. I've never seen the low side get that low. The ac pressure switch should be turning the compressor off. Be that as it may, it looks like a blockage, normally this is the expansion valve. I would change that out.

Wing Nut

Hey, thanks for the response Holmesnmanny. I'm just looking for a little confirmation to make sure I'm not missing something before I go and tear into everything.

Apex1972

Has anyone here heard of the problem with the small pellets that are inside the drier causing the system to get clogged up? I read a very detailed thread awhile back from a guy with a 4th gen Prelude. From what he said,it was a fairly common problem.

Mykizism

Wing Nut, A few things you might will want to replace.

The expansion valve inside the evaporator core and receiver dryer behind the front bumper.

You will have to evacuate the system, then replace those items. After that you can process to recharge the system.

If the AC gets cold, but cant "keep" up on hot days is usually the expansion valve.

Parts List:
80351-S30-A01 RECEIVER
80220-S30-003 VALVE ASSY., EXPANSION

Mykizism

Replace Receiver and Expansion Valve.

Wing Nut

Thanks a lot guys. I'll definitely reply when I get a chance to replace those items. The only difficulty is that here in Pensacola the weather is already cooling off, so I may not be able to effectively test it once I get it replaced. We'll see what happens.