ryosuke

Hi all, I have been troubleshooting a problem with my air conditioning for the past couple of weeks. I have searched and found a couple of threads with what seems to be the same issue, but I've been unable to resolve the problem.

I have a '93 Hatchback that has a used R134 system from another Civic ('94 or '95 I think) in it. I installed it at the beginning of the summer, and it worked great up until about a month ago, when it became intermittent. I eventually tracked the problem down to the A/C switch in the control panel. I resoldered the switch, and it worked great for a couple of weeks, and then it quit working altogether. When you press the A/C switch, the engine RPM increases, but the condenser fan doesn't kick in and the compressor clutch does not engage.

I went through the flowchart in the manual, but it leads me to a bad ground wire, which I then verified is not the case. I've done some additional troubleshooting and have found the following:

I have verified that the No. 35 and No. 13 fuses are good.

I have tried shorting both the thermostat connector and pressure switch connector, with no luck. I have also verified continuity across both of these sensors with a multimeter, so I do not believe either of them to be bad.

I have verified that the condenser fan will run, and the AC clutch will engage on battery power.

I checked the voltages at the condenser fan relay and found the following:

Ignition ON(||) A/C OFF
Yellow: ~12v
White: ~12v
Y/W: ~5v
Blu/Blk: 0v

Ignition ON(||) A/C ON
Yellow: ~12v
White: ~12v
Y/W: ~0.1v
Blu/Blk: 0v

Engine running A/C ON
Yellow: ~12v
White: ~0v
Y/W: ~0.1v
Blu/Blk: 0v

It seemed odd that the voltage on White drops to 0 when the engine is running, as that appears to come straight from the battery. Either way, the condenser fan does not run whether the ignition is on or the engine is running.

I found that if I short Blu/Blk to Yellow, the condenser fan motor would run, the compressor clutch would engage, and I would have cold A/C. However, I am unable to determine the root cause of the problem. I do not want to short this connector, and risk damaging my system. I know there are some experts on this stuff on this forum. Any help is appreciated. Thanks!

ryosuke

One thing I forgot to mention last night... The wiring diagram I found for the '94-'95 cars shows three wires going to the thermostat, while my car only has 2 wires going to the thermostat. Is this a problem? I don't suspect it is, since the system worked fine a couple of weeks ago.

I really hope to figure this out in the next couple of days. Today the high is a 'nice' 92 degrees, but it's supposed to be close to 100 degrees by the weekend...

Former User

Was this^ test done in the fan relay socket with the fan relay removed?

Also, the stock wire color for your car should not be Yellow. It should be Blk/Yel (see diagram). Is your wire actually Yel or is it Blk/Yel?

Under the conditions of this^ test, the voltage at the Yel and Y/W wires should be identical (12V). This suggests that the fan relay is bad. If you swap the fan and clutch relays, does the fan now run with the key in ON(II) and the A/C button pressed?

ryosuke

Hi RonJ, Thank you very much for the reply.

Yes, the test was done with the fan relay removed from the socket.

I'm surprised that I didn't notice this, as I was looking at the same diagram last night. The wire is definitely Yel, and not Blk/Yel. I popped the base off of the socket so that I could take a better picture of the pins:



You can see that one pin has a Yel/Wh and a Yel wire attached to it, and another has just a Yel wire. What could this mean? the wiring looks original to the harness, but I'm not sure the year of the car that the A/C harness came out of. Would it be a problem if the year of that car was different than the year of my car?

Is this under the expectation that the test was performed with the relay in place? Because I removed the relay from the socket when I did the test. In any case, I tried swapping the relays and no luck. The fan still does not turn on. Thanks again for the help.

Former User

This^ tells you that the A/C circuit is miss-wired because the condenser fan should run but the compressor clutch should not engage when fan relay socket terminals B and C are jumped. It appears that the Blu/Blk wire has been spliced into the Red wire that runs to the compressor clutch.

If you jump A (Wht) to B (Blu/Blk) in the fan relay socket with key in ON(II) and A/C button pressed, do you get the same result as jumping B to C?

Post a similar picture showing the wires at the rear compressor clutch relay socket.

You should also test both relays. They both may be bad.

Oh okay. The 5V at the Yel/Wht wire terminal is coming from the ECU. The voltage drops with the A/C button pressed because this grounds the voltage from the ECU.

Former User

This^ is indeed unexpected.

ryosuke

Thanks again for your help. I really do appreciate it.

That doesn't sound good. I guess I will need to use a multimeter to verify proper continuity between all the components in the schematic?

No. This is something that confused me. If I jump A to B, the fan does not kick on, but if I jump B to C, the fan does kick on.

I'm just getting ready to leave work now. When I get home, I'll post up another picture. I tested the relays a while back when I was having trouble with the control panel. However, I will retest again when I get home.

Former User

Not good, but easy fix.

Definitely a good idea. I expect that you will find that the Blu/Blk wire has continuity with both the compressor clutch and the condenser fan.

Did you try the A-B test with the key in ON(II) but the engine off? In this case, the fan should run and the compressor clutch should click.

The A-B test would be expected to yield a negative result with the engine running because, in this case, the Wht wire lacks voltage.

ryosuke

So I performed this test:

Blu/Blk on the fan to Blu/Blk on the on the relay -continuitiy
Blu/Blk on the relay to Red on the clutch - no continuity

This seems like good news at least. I did not completely pull the wrapping away from the red wire that goes to the clutch, but it feels like it goes straight from the clutch to the clutch relay. Here is a picture of the back of the clutch relay socket:



I also tested both relays. They both tested out the same:

De-energized
A-B: No continuity
B-C: Continuity tester did not go off, so I checked resistance and both measured out at ~105-110 Ohm

Battery voltage over A-B:
B-C: Continuity

Now in the manual page that you included, it shows that there SHOULD be continuity between B-C with the circuit de-energized. However, given that they both switched on with the battery applied, and given the resistance, I am inclined to believe that they are okay. What are your thoughts?

Yes, I did the A-B test with the Key in ON(II} but the engine off. The result was the same. The fan did not run, nor did the compressor click. Does this indicate an open somewhere in the white wire?

Former User

Hmmm...the compressor clutch must already be engaged even before you jumped B to C in the fan relay socket. In this case, the only electrical problem in the A/C system is that the condenser fan doesn't run.

Two Wht wires and two Blk/Yel wires?

You are doing the relay test incorrectly. You need either to apply no voltage or voltage across C-D and then measure continuity across measure A-B.

This is completely unexpected.

Former User

Repeat this^ test with the key off.

ryosuke

Well the compressor clutch is not engaged, at least not when the engine is running. I did not attempt to test whether the clutch was engaged when the engine was OFF, but ignition was ON.


That is correct.

My apologies. What I posted makes no sense. I'm fairly certain that I actually did the test correct, and just recorded my results incorrectly. I know for sure that I did not measure continuity across B-C. It was either A-B, or B-C. However, I will double check again tonight, and also redo the test that you mentioned in your second post. I would really like to thank you again for helping me with all of this.

In other news, some ******* hit my mirror when my car was parked on the street last night. Luckily, there is only a couple of small scratches on the cover, but I took it apart and the mechanism inside is broken. So it looks like I'll be going to the junkyard this weekend. If I can't get this figured out by then, and it makes sense to look for any A/C components (ie. wiring), let me know.

Former User

Your A/C wire harness is clearly modified, so I recommend that you pick up the entire A/C wire harness from a stock 93-95 Civic. This will probably solve your A/C problem.

In the meantime, it would probably be informative to do more continuity tests with fuses 13 and 35 and the two relays removed/unplugged. Each relay connector has four pins. With the fuses and relays removed, test each pin in the fan relay connector for continuity to each of the 4 pins in the clutch relay connector (16 separate continuity tests). Post the test results, indicating pins that have and do not have continuity.

ryosuke

Thanks again RonJ. I'll do the continuity test tonight, and I'll look for a clean wiring harness this weekend. Do I need to worry about the year of the car beyond it being a '93-'95. The reason I ask is that my car has a 2-wire thermostat, while I saw in diagrams for newer cars that they had a 3 wire thermostat.

Former User

Was your car converted from R12 to R134a? If the harnesses are cheap, get both types as well as the 3-wire thermostat, and also pick up the heater subharnesses.

ryosuke

Yes, my car was originally R12. However, it did not have the usual Honda system in it. All of the lines were soft lines, and all of the components were different. Additionally, the A/C wire harness was different. The relays were standard SPDT automotive relays, and most of the connectors different, with the exception of the one that hooks into the main wire harness.

Thanks for the info about the heater subharness. The one in my car appears to be standard, but I'll grab another one if I can, just in case.

Former User

The best case scenario would be to get stock wire harnesses from a 93-95 Civic with a stock R134a A/C system. The complication is that I'm not sure whether you'll need to remove the evaporator to install the 3-wire thermostat. I'm hoping that the thermostat can be replaced without removal of the evaporator or by cutting and splicing the 3-wire thermostat to the 2-wire temp probe. Maybe somebody else can chime in.

ryosuke

Alright. I didn't have a chance to do anymore testing last night and I probably won't tonight either. I'll try to find a R134a car tomorrow and hopefully be able to grab both the A/C harness and the heater subharness with the 3-wire thermostat. I've removed the evaporator before. It's not fun due to the location, but it's not terribly difficult either.

ryosuke

I thought I should post an update with my progress from the weekend. I went to the junkyard, and pulled the A/C wiring harness from a '93 car, as well as the complete A/C harness and heater subharness with thermostat from a '94 car. My plan was to try the '93 harness first, and if that didn't work, swap in everything from the '93. Well, luckily, the '93 harness seemed to solve the problem. A/C has worked consistently since the change.

I still have not yet gone through the old harness in my car, but I would like to do so, as I would like to know what exactly was causing the problem. Once I do, I'll update this thread.

Thanks again for all your help RonJ! You were right about the evaporator by the way. I pulled the evaporator on the junkyard car to get to the thermostat, and see if it was possible to swap on the car. It is not. The thermostat itself is removable without removing the evaporator, but the probe isn't. It's threaded through a little hole in the case that is not accessible on the car. It is a simple 2-wire probe though, so my thought was that I could splice the wire if I had to. Luckily, none of that was necessary.

Former User