Megacam

Hey all, new guy here and new to Hondas. having some weird issues with the A/C on my '07 Civic LX. I'll try to keep it short and sweet...

Initial problem: Compressor clutch would not engage for long spurts of time and finally quit engaging altogether.

Solution: found that the field coil was bad, and replaced with a good used field coil, pully and plate.

Current problem: As soon as the new field coil was installed the clutch was engaged all the time...even with panel **** turned to "off". Test drove it and clutch seemed to be working as it should, IE, on and off as it's supposed to do.
Wife drove car to work and said the air was hardly coming out of the vents and had a large puddle under the car after sitting for about an hour. To me this seems like the low pressure line was freezing.
Test drove it that night and all seemed well, except I parked for 5 minutes and let the car run with it on regular A/c and could feel the compressor kicking on and off every few seconds. switched it back to max A/c and drove around and it seemed to work as it should. No sign of frozen lines.
Wife drove car to work in morning and said air was ice cold and perfect. She then drove car in mid afternoon and said the air was blowing strong, but only "hot" air. I test drove it tonight and air seemed to work fine. I tested the relay by swaping it out and also tested the relay sockets to make sure they were getting the correct signals.
Seems to me it's something electrical. Of course it always works fine when I'm testing it, and always malfunctions when wifey is driving it.
What else should i be checking? Maybe the ground from the ECM? Maybe the Pressure switch? Thanks for any help you guys can give to help me figure this out.

ezone

#1) How much clearance does the clutch have? If clearance is insufficient, the clutch will drag or stay engaged. Spec is 0.5mm +/- 0.15mm.

Unplug the compressor while it is stuck on to eliminate electrical as a cause. Plug is on top of the alternator.


#2) If the compressor is being driven all the time through an unintended cause, you have a few problems happening:

a) The the evaporator core can freeze into a huge freeking ice cube after the compressor has been spinning for so long without cycling (supposed to cycle off at around 37 degrees to keep the core from freezing). Zero airflow goes through it once it freezes. It leaves about a half gallon of water on the ground when it melts.

b) The condenser fans aren't running, therefore the system gets overpressurized when there is no airflow through the condenser (engine may buck due to compressor resistance), and if the system pressure hits about 450 PSI (IIRC) the freon vents out to atmosphere through the high pressure safety relief valve. Now the freon is low, but there's still just enough to let the system run, but it won't cool as good.
Low freon will make it be very inefficient when it's hot out (noon sun), yet it might feel adequate while it's not so hot out (evening).


We do have problems with the original relay sticking on and causing all these same issues, but you swapping relays should have eliminated that as a cause.

This part sounds a lot like an overcharged system, bouncing off the high pressure cutoff switch.

If the compressor clutch was mechanically driving the compressor without any electrical influence, the system would vent instead of having the high pressure switch cut the compressor off. Pressure Switch cuts off around 400 PSI or so.


If the ENGINE is overheating, the PCM shuts off the AC compressor too.


I'd check the clearance on the clutch, then plug in my scanner and watch live data for the AC system and coolant temps, and probably connect AC pressure gauges to see what's going on inside the AC system.

HTH

Megacam

Thanks for the input ezone. Already have done some of these tests and here are the results:

1. clearance was good with feeler gauge. To check I unplugged the relay and the clutch disengaged, so it's not mechanically "stuck".

2. a) I think the freezing evap. core is what may have happened to wifey a few times when it would not blow strong through vents and puddle under car after sitting parked.
b) the condenser fans seems to work fine. It is always on when the A/C is on and running. Not sure about with A/C switched to "off" and clutch still engaged as it seems to be doing.

Lastly:
Engine doesn't seem to be overheating at all. gauge in dash looks fine and no sign of overheating by looking at engine. We put alot of miles on this thing and I think that would be a obvious issue, but I'll double check.

I did add a bit more coolant to the system (with a large tank on a scale as not to over-fill). I think I did over fill it a bit as the clutch started to click on and off repeatedly in a matter of seconds (on, off, on, off, ect.) So I bled some coolant until the clutch stayed engaged.

Maybe I didn't bleed enough? I believe the low pressure side was reading around 22 PSI where the clutch was engaged. What are safe PSI levels to have it at?

Unfortunately I don't have the type of scanner you have, I just have an OBDII scanner. Checked it last night and got an emmissions code P0420.

So, if I get the Proper level of coolant...I still have the problem of the clutch staying constantly engaged. Could improper coolant level cause this?

ezone

The condenser fans don't run unless the climate controller is operating the compressor.
If the relay stuck on causing the compressor to run continuously, the fans do not run (unless high coolant temp turns them on).

You got the defroster on? The AC runs with defroster on.
You mean freon R134a. Please use the term "Freon" or "refrigerant" instead of "coolant", as coolant commonly refers to engine antifreeze.

Yeah that sounds overcharged. Check your high side pressure while it's clicking on-off-on-off, I bet the pressure will be quite high.



"Correct" operating pressures are huge variables, depends on the system and conditions it's operating in.



Did you swap out the wrong relay? There are several that have to do with AC but only one that controls the compressor clutch.



Clutch relay goes in the spot marked #5 here in the left half of this pic:


Check clutch make sure it is stuck on, then tap on the relay see if the clutch lets go.
If it was stuck, replace this relay with updated part:
Updated relay brand is MITSUBA
Updated Honda part number is 39794-SDA-A05

Megacam

Yup, condenser fan is operating as it should.

No defroster on.

Yes, I meant refigerant not coolant (was in a rush when I typed that out, lol). Yes, I'm using R134a.

Hard to check the high pressure side because the clutch is engaged all the time. It seems to "feel" like it cycles on and off while driving, but when I stop to check it, the clutch stays engaged constantly. Maybe i'll drive it a bit more and see if I can get it to replicate the on-off-on-off scenario.

Yup swapped the #5 (in your diagram) with the #3 radiator fan to test and got the exact same results...and also the radiator fan worked with the #5 in its socket. I'll try to tap it, but I'm pretty sure the relay is good.

What else would cause the clutch to stay engaged all the time, even with the control **** turned to "off" position and defroster off?

Also, thanks for taking time to try and help me.

ezone

Crap. Kinda going 2 different directions with possibilities here.

You say the fans are operating, but are they operating with the compressor engagement, or only operating with the engine coolant temperature?

If the fans are running with the compressor, then the PCM is operating the AC system for some reason.
If the fans only run because of high coolant temp, then this should point to an electrical issue only affecting the compressor and/or it's control circuits.

Um, just how did you plan to check this?



If the clutch were really stuck on......
I'd probably start tests at the clutch relay to see where the next test area will be (each answer determines the next question).

Does the clutch disengage when you remove the relay?
Is the relay being activated electrically?

Wiring diagram, test light and voltmeter....Actually, I'd plug in my scanner to check the status of the AC request To the PCM, and AC clutch control BY the PCM first. (If something inside the passenger compartment is asking the PCM to run the compressor, then the issue would be inside the passenger compartment.....)

Megacam

going to do some more checking and I'll update in a day or two.

Megacam

The condenser fan is operating with the compressor

Megacam

[quote=ezone;4663615]
Um, just how did you plan to check this?[quote]

I can check with a manifold gauge set, like this
http://www.harborfreight.com/a-c-man...set-92649.html

Megacam

Hmm, having trouble trying to quote
Anyway...

"I'd probably start tests at the clutch relay to see where the next test area will be (each answer determines the next question)."

I've tested the relay socket the following ways:
1. tested the voltage from terminal #1 with ground = good
2. jumped terminals #1 and #2 to check clutch engaging = good
3. with ignition on, tested voltage between terminal #3 and ground = good


"Does the clutch disengage when you remove the relay?"

yes is will disengage

I did forget to actually test the relay itself with a voltmeter

"Actually, I'd plug in my scanner to check the status of the AC request To the PCM, and AC clutch control BY the PCM first."

I don't have this type of scanner. Sounds like a special Honda type of scanner.

Update: I drove the car for about 45 minutes on Sunday and the air was Ice Cold and working just fine.

Update 2: my wife just called me and stated that after driving 20 minutes it is hardly blowing any air. Evaporater must have froze again

ezone

What about the 4th terminal?
This will be a ground -- supplied by the PCM -- present when the clutch relay is to be turned on.


Forget it.
You removed it with the compressor running, and the compressor shut off. If you could feel the relay CLICK as you removed it from the socket, it's working as it should.

You can't check if it will get "stuck on" unless/until it actually happens, other than seeing the brand name on it.

Yup. HDS.

Got a fast acting digital thermometer? If the vent temp is below about 37*F, it might be too cold.

I got a couple from WalMarts' kitchen section, they work great. Pretty accurate and darn quick to react to minuscule temp changes. I can watch the temps go up and down as the compressor cycles on and off.
Seems like you need to catch this in the act of failure to figure out what is really going on.
I think 2 possibilities at this point: If the fans are still running when it froze up, then the PCM is still operating the system and it's likely to be an evaporator temp sensor problem.

If the fans are not running but the compressor is still running:
a) tap on the clutch relay and see if the compressor disengages.
If it does not, then
b) check the 4th terminal at the clutch relay for ground (as mentioned above), to see if something electrical is holding the relay on.

Megacam

uhhggg. It always seems to work fine when I check it...although the clutch is always engaged when I stop and pop the hood. It also seems to cycle on and off when driving.

I did check the relay sockets and #1 and #2 have constant 12v with key to "off".
With ignition to "on" the #3 and #4 also get 12v. But as i stated, it also is always working when I'm driving/checking it.

I'm almost certain that it's something electrical causing the clutch to stay engaged (even with control **** to off), and I'm wondering if that's what caused my original field coil to burn out.

I think I'm going to take it to an auto elecrical tech who has a small shop in my town and does a really good job. He has all the scanners, schematics, ect. to check it out.

ezone

It should cycle. It's supposed to cycle the compressor off when the evaporator core temp is around 37-40 ish, then turn it back on at a few degrees higher.... so the core doesn't freeze water. Maybe a 4-8 degree window of cycling off and on.

That's the usual scenario for the stuck relay, but I guess you have to catch it in the act to prove it or test it.


Again, hard to prove now IMO. I have seen plenty that had the relays stuck on for a long time without killing the clutch coil (I know that doesn't mean much LOL). The coil can have a thermal protector built in, or it could have just gone bad. It happens on occasion.

HTH

Megacam

Update: Took the car to the Auto Elecrtical Technition last week and he told me his scanner was reading that the control **** is sending an "on" signal even with the controls turned to off.

This weekend I took the dash apart and unplugged the A/C controls. Started the car and the clutch is not engaged

So, it looks like I need to replace the A/C controls. Now to find them as cheap as possible. Not sure if I should risk used or not...guess it depends on price.

Again, Thanks for all your help

ezone

On an 07, that's a totally new failure for me. I'll have to remember this.


The control head is different between 2 door and 4 door cars, but looks like about $115 at internet wholesale dealers.
http://www.hondaautomotiveparts.com/

Listed in 'heater controls'