AC repair / recharge questions

[sona1111]

Hello. I was going to attempt an A/C repair this summer, but I have heard it can be hazardous, so I had a few questions first.

[1989 accord LX auto]

When first obtained car about a year ago, AC was not working, unknown cause. 6 months later realized I had serious engine issues so I took it over a friends to do a swap. In the middle of this, we ended up unbolting the compressor as the system was not working anyway and it was in the way of something (don't recall exactly, but I now know that it is bad to remove that system under pressure for environmental reasons). A large amount of gas escaped, so it seems that there were not any serious leaks in the system. Now the car still has no compressor, and I would like to attempt to get it working again.

I have seen the tutorials of evacuating the system and refilling for 134a type systems. It does not seem too bad. However there are still a few unknowns. I have the big, Denso type compressor, which I have found are readily available online, so that's fine. However I am unable to find any indication of which type of refrigerant I should be using on the underside of the hood. If I completely vac out the system, is it ok to use R14, or is there some other way to find out? Also, what type of oil should be used in the R14 system?

Appreciate any insight.

Thanks for reading!

[Dr_Snooz]

Does your system have the 134 retrofit ports on it?

[Oldblueaccord]

R12 is the old Freon. you wont find it any more. R134a is what you can still buy over the counter in most states. I have had great luck with the conversion.

Best tip for safety is always fill the LOW side of any system. On our cars its the think rubber hose going across the front of the engine.

[sona1111]

Hi! Just to understand, by 'conversion' you mean that the old Freon (R12) has been vacuumed out and R134 added, or you mean you must replace all fittings / hoses to accept the newer Freon? All of the parts look stock to me, but I have not yet measured the diameter of the fittings to verify. If all parts must be replaced, I think I would just go for ordering R12 online, unless you think this would be a bad idea.

[Oldblueaccord]

Hi! Just to understand, by 'conversion' you mean that the old Freon (R12) has been vacuumed out and R134 added, or you mean you must replace all fittings / hoses to accept the newer Freon? All of the parts look stock to me, but I have not yet measured the diameter of the fittings to verify. If all parts must be replaced, I think I would just go for ordering R12 online, unless you think this would be a bad idea.

The R12 fittings and the R134a fittings are different to keep from mixing the two.

The only thing you really needs is the correct oil for r134a in a Denso compressor and they make conversion fittings that fit over your low and highside ports.

That being said I never used the conversion fittings on my car I made a hose that is R12 on one side and r134a on the other.

Vacuuming the systems down is more to remove moisture than anything else.

Also a new drier is in order.

The online howtoos are pretty good.

[sona1111]

Ok, that does not sound too bad: I will put on the adapter fittings, new compressor, and fill the system with correct oil and R134A. What is a 'drier?' never heard of this part before. From searches it is just that little black canister on the driver side?

[Oldblueaccord]

Ok, that does not sound too bad: I will put on the adapter fittings, new compressor, and fill the system with correct oil and R134A. What is a 'drier?' never heard of this part before. From searches it is just that little black canister on the driver side?

Desiccant dryer helps pull moisture out of the systems.

Yeah its jammed down in that hole on the drivers side.

[Dr_Snooz]

I would recommend having a shop fix the A/C system. If you don't know what you're doing, you can cause some expensive damage and potentially hurt yourself badly.

[gp02a0083]

I would recommend having a shop fix the A/C system. If you don't know what you're doing, you can cause some expensive damage and potentially hurt yourself badly.

As Snooz said, if you don't know what you are doing with the AC system you have a very good chance of hurting yourself and/or damaging the car.

regarding the dryer, some shade-tree guys have gotten away without replacing it and just pulling 30inHg of vac for an hour or so. in my opinion desiccants usually require heating in addition to vac to make is absolutely dry. Replacing this is relatively easy and usually cheap, just annoying you have to remove some clips for the wheel well liner to access the mount/bracket. My only tip here is to make note of the arrow/direction of the old dryer as they are not bi-directional.

As far as the R12 to R134 retro fit goes:
1. easy to see if retrofit ports were installed, R12 has the same size ports for both high and low sides, R134 has a smaller diameter low side and a larger diameter high side.
2. As you found out, make sure the oil you use is comparable so that you don't create a off pH or goo that'll make a mess in the system.
3. Install new shrader valves, they are like valve stem cores. usually they come with the retrofit kits. about 80% of the time in my experience have been related to the shrader valves.
4. As Blue mentioned, always ALWAYS! charge the system from the low side port ( Blue is correct as it is the line that runs across the front side of the engine with the port toward the battery.)
5. Pull 30inHg for a minimum of 30 min. ( i prefer 1 hour, then close off the manifold and see if the system maintains the vac level, if not you got a leak somewhere)
6. A manifold w/gauges is very very important! This can tell you how well the system is working and possible issues ( like expansion valves). The little cheezy A/c Pro cans with the gauge from wally world / p-bo/ or shitzone is a wast of money IMO.
7. Wear safety glasses
8. sit back have a beer and hopefully enjoy the ice cold AC

[Dr_Snooz]

This topic comes up from time to time, with me telling the OP to take the car to a shop and everyone else telling the OP to dive in. So let me make my case more thoroughly.

1. You need a couple hundred dollars (minimum) worth of specialized tools to service your own AC system. Mainly a manifold gauge set and a vacuum pump.
2. If you don't know how to read the gauge set, it won't help you. If you don't know how to connect the gauges and pull a vacuum, they won't help.
3. If you don't know how to get all the freon out of a can, you won't be able to charge the system properly.
4. The AC might have other problems that the gauges will reveal, if you know how to read them. If you don't, then after all that expense, you'll still be taking the car to the shop to figure it out.
5. If you don't know what oil you have presently, then you'll need to completely flush the system, which requires a complete disassembly or a very expensive flushing machine. Since you've had the system open for an extended time, you should do this anyway or risk damaging the system. If you opt for the disassembly, you'll at least need an air compressor and a blower attachment and some very big wrenches.
6. If you don't know how to install the 134 retrofit fittings, they won't work and you won't be able to service the system. Most likely, they'll leak and you'll lose $20 worth of freon.
7. Given the age of your system, you're going to have leaks, which will require more expensive specialized tools and a lot of lost freon to find.

Since you don't know what 134 retrofit ports are, then you either have a LOT of research, expense, trial and error ahead of you, or you can take it to a shop. Don't get me wrong, it's worth learning to do all your own work, but you won't be ready to do this project by summer.

[sona1111]

Hey Guys,

Thanks for all of the tips, I have taken it to heart when trying to go through this job. I have reached a point where I think I will need some advice. Here is the situation so far:

-r134 fittings were already installed
-replaced compressor / added new oil (new o rings)
-replaced drier (new o rings)
-vacced system for a few hours ; -30psi pressure held overnight without leaking at all.
-proceeded with charging procedure.

At greater than 60PSI pressure, fans come on, but compressor does not. Same happens if pressure switch is bypassed.
I went to the shop manual to proceed through the troubleshooting steps, checked fuse, relay, got to delay control unit where it said to inspect it, so back to page 23-6. At this point I tested all of the connections, but for the Red/Blue one, it said that if A/C clutch does not come on, there is a fault with the delay relay in the delay control unit. So arriving at this point, I am wondering if there is any way to bypass the delay switch? The idle is higher than usual anyway so I doubt I would notice. Otherwise is there any way to repair the delay switch itself? I have no idea how I would find a replacement for this unit that is not super expensive at this point.

Appreciate any suggestions!

Thanks for reading.

[sona1111]

Additionally, I just took off the delay control unit itself and upon opening it, it looks like the worse piece of electronics I have ever seen. Completely rusted out and a few components just fell off the board when I opened it.... :nuts:

Pretty sure that is the issue...

[sona1111]

So basically, I could get it to work by wiring the yellow wire to the black wire through a second switch - I just have to turn on both that and the other AC switch. Feel free to let me know if this is a really bad idea. :)

[Oldblueaccord]

I think you would be ok to by pass that. it just cycles the temp and the compressor so they dont run 100%.

Sounds like you are on your way with the AC. I dont think you will need more than 50 psi on the low side just my experience.

[gp02a0083]

Snooz reiterates important info

i'm with Blue, 60 psi is kinda high if you are talking about low side pressure. should be 45-50 psi max even when its really hot outside.

holding that level of Vac overnight is a good first sign that the system is buttoned up well and does not have any substantial leaks.

i'm a little confused as you what you are bypassing as i do not have the wiring schematic nearby. I do recall the interior AC switch , low pressure switch, blower fan switch and one other is ganged in series, did you by any chance also rule out the diode box? i'm just curious being that also the control unit also is wired to the idle boost

[AC439]

I have mine converted to R134a for many years and it still runs excellent. I did not even bother to put the adapter on the high side. Center vent temp get down to 40F in Florida hot summer. I only charge on the low side with a gauge. When it hits 35 lbs when ambient is 70F I will stop. When ambient temp is 80 or 85, I will stop when low side pressure around 40 to 45.

I think your issue now is electrical and I would bet on the clutch circuit. Since when you press A/C button, your fan turns on (and vice versa), the A/C delay unit is at least working partially. This unit is the one under the front passenger side fan blower. The yellow line on the box will ground the A/C clutch relay and energize it so it will provide power to the a/c clutch. I think this is the yellow line you are referring to but not sure what black line you are talking about.

I would check the a/c clutch relay's functionality. You also don't want the a/c compressor to run constantly. Its supposed to be cycled according to the thermostat (inside evaporator). The delay timer lets the a/c idle boost activate (vacuum circuit controlled by ECU) first, increase engine rpm, then engage the a/c clutch after 400 msec.

I think you are close to getting it working. I would definitely check a/c clutch relay and continuity between the relay's coil and the delay timer.

60 Psi is the static pressure of r134a since your compressor is not turning. It will go down once the compressor is running on the low side and go up on the high side.

[AC439]

Forgot to mention the location of the delay timer sometimes will let water accumulate, especially if you have water leaking inside through the air box where the blower fan sits. Mine was wet one time and a/c was not able to turn on. Got it out and dry everything, plug it back in and working like a champ. You may have to check the solder points for dry joints as well.

[sona1111]

Hey Guys,

I appreciate all of the follow ups. Let me clarify a bit: The problem was 100% with the delay control board, both from following troubleshooting manual, and because it was completely rusted inside (likely due to the water ingress issue you mentioned). I may likely look for one in a junkyard at some point, but I am not sure how else to replace it and verify that the new one is not also broken. I get about 50 pressure when the compressor is not running, and bypassing the delay board to turn on the compressor, the AC works great. (idle is already high, because of other carb mysteries, so it is still completely drivable with AC turned on and lower idle). Current hacked setup is just a toggle switch wired to the YELLOW and BLACK wires of the cable that the delay control board used to be hooked up to , so I turn on the AC switch (light comes on, internal fans come on and two cooling fans come on), and then turn on the hacked switch, which starts the compressor. The only real concern I have for this setup is that the compressor is on all the time, I am not sure if this will cause any damage over time. (?) However there don't seem to be any leaks and at least I am happy for now...

[AC439]

Coil may freeze up if compressor is constant on. The function of the delay unit is to only providing a 400ms delay (to power the clutch) after A/C switch is on so the engine has time to boost a little higher rpm. If my delay unit is broken, I will build a timer board using timer IC NE555. Using the datasheet, you can calculate the RC values for 400 ms delay. I have not seen a 3rd gen accord in junk yard forever so this will be one of my two options. The other option is to take apart the delay unit (which I had before), clean up the circuit board well, replace any broken components.

Another idea is to built a timer board to give the compressor a variable duty cycle, say adjust it from 20% on 80% off to 100% on (for hot days). Again, can use a NE555 timer IC with a variable resistor for duty cycle adjustment. The IC can drive a relay which in turn replace the hack switch to cycle the compressor.

[gp02a0083]

Coil may freeze up if compressor is constant on. The function of the delay unit is to only providing a 400ms delay (to power the clutch) after A/C switch is on so the engine has time to boost a little higher rpm. If my delay unit is broken, I will build a timer board using timer IC NE555. Using the datasheet, you can calculate the RC values for 400 ms delay. I have not seen a 3rd gen accord in junk yard forever so this will be one of my two options. The other option is to take apart the delay unit (which I had before), clean up the circuit board well, replace any broken components.

Another idea is to built a timer board to give the compressor a variable duty cycle, say adjust it from 20% on 80% off to 100% on (for hot days). Again, can use a NE555 timer IC with a variable resistor for duty cycle adjustment. The IC can drive a relay which in turn replace the hack switch to cycle the compressor.

haha my father had taken our family's spare civic and rigged a toggle switch for the compressor as well ( A/C circuits in the ECU fried ).

not a bad idea using a simple PWM circuit with a trimmer for adjustment. I am curious as to what is in the delay box and how far rotted it may be. wondering if its just simple components that can be replaced before

[AC439]

The delay unit is relatively simple in terms of technology (back then 80's). You can trace out the PCB and deduce a schematic. Mine stopped working when water got inside. I yanked it out and had it dry it completely. I then re-soldered suspect cold joints and it has been working since. However, I did not put it back in its original location since water can get in when there is heavy rain. I had it relocated a little bit towards the right side.

555 is enough for this purpose. You just need a simple timer for duty cycle (you are not doing any pulse wide modulation). But I think you can repair the delay unit rather than fabricate something new.

[InAccordance]

Side note: You can get r12 off ebay.