kwkenuf

Daughter's car, 2007 Civic EX automatic. 128K miles. Owned it since new. Normally very reliable.
A/C quit while driving on super hot day, 115 plus. Blower functions, compressor not engaging. Has over 100 psi residual verified with good set of gauges. Followed a couple of threads on this forum. Forum member Ezone very helpful! Hope he's tuning in here.....
Verified clutch relay good and 12v on both sides of relay; control and opposite of load connection with ignition on and a/c selected. Kept troubleshooting expecting to find bad clutch coil and I did. Infinite resistance at relay location and also at connector on top of alternator. So I'll need to fix that but here is where it starts to get weird.
A/C clutch relay is not getting a ground from the pcm when a/c is selected. So even if the clutch was functional (it seems to have a bad coil, has infinite resistance and won't engage when jumped) it would not operate since the relay would not have the necessary ground.
EDIT: The red text is in error. Condenser fan motor does not operate and cooling fan shuts off when A/C is selected. (with engine off but ignition on). Both fans operate at high speed when you first turn ignition on but stop if you select A/C. Fans do operate when engine is running but condenser fan motor will shut off with A/C selected. The fans switch to low speed with ignition on, A/C on. And they do not switch to high when A/C is selected when engine is running. A/C pressure sensor connector reads 5v, 1.4v, and ground on the three pins. No faults detected during control panel self check. Normally fans not running means low refrigerant charge but that is not the case here. I'm hoping this is not a pcm issue. Not wanting to surrender but running out of ideas. Can anyone throw me a line? Thanks!

ezone

See if clutch relay receives ground whe the HVAC panel is turned off. You said the fans run at that time so let's see if the clutch relay is powered up at the same time.


Then unplug the 3 wire comp connector and see if that shuts down the fans as well.


The center wire of the 3 pin conn is the field coil, the other two are for the thermal protector--if that is open it will shut off the ac system (compressor and fans should all cease).

kwkenuf

Will do. Thanks for the quick reply. One large omission on my part and this may help. When I first started troubleshooting this issue and before I had read your previous fault analysis on another thread or even so much as peeked at a schematic, I did have fans running as one would expect with a charged system. That changed during the course of my initial efforts when I was following someone else's advice to jump the pressure switch connector. (old school) And now with the benefit of a schematic I see that I jumped pcm 5v and v-out to ground on that connector....

kwkenuf

Results of above:
No ground at clutch relay when key on, A/C panel off.
Fans shut off when 3 wire comp connector disco'ed.

edit: I have an earlier reply stuck in moderation about a mistake I made that I suspect will be relevant

ezone

Pressure sensor......You didn't jump 5v to ground, did you?

kwkenuf

Probably... See post 3 above. Self induced PCM roasting?

ezone

Does the pressure sensor still have 5v, ground, and 1.4v as on the first post?

kwkenuf

That was it's last condition after things went funky. I'll check again to make sure nothing has changed. Thanks again for the help... Back shortly....

kwkenuf

Looks like a change or my first readings were in error.

4.7v center pin
5.02v outside pin
Ground other side.
Sometimes a tiny bit of resistance on the ground pin but that might be me and my meter while using jumper to touch pin. (meter lead too large to reach contact in connector)

edit: these readings are taken from the disco'ed connector, not by probing the wires while connected to the sensor....

Fans shut off when connector disco'ed while key on. If key off, then connector disco, then key on, fans run for a short period, then shut off (key on self check I expect). You didn't ask but I thought it might be relevant.

ezone

Ok seems as though the 5v for the pressure sensor hasn't been ruined, but it would be handy to be able to view the sensor reading on a PCM datalist. Right now I'll assume it's not harmed because:

You say the fans shut off when you unplugged it.....so the PCM can still see it and kills the fans when it loses that input value. So far so good.


Got any PCM fault codes? Post em if you got em.
You probably set extra codes by dinking with the pressure sensor, so you may need to erase codes (P0532/P0533?) IDK if that will prevent the AC from operating now, but it's a possibility.

====================
I notice you keep checking stuff with the key on but engine off.
When you check if things are operating, start the engine up and at least let it idle. Then note if radiator fans are on, blower fan in the dash is on, compressor clutch relay engaged, etc.
I'm going to assume there is no change while the engine is running.....so.....

The HVAC panel sends an "AC request" signal to the MICU (Hondas name for body control computer) when you turn the AC on.

The MICU sends that request signal to the PCM through a communication network

The PCM looks at the AC pressure sensor, coolant temperature sensor, throttle position, and some other stuff and if all is well, it turns on the relays that run the compressor clutch and both radiator fans. (3 relays are used to make the fans run on low speed or high speed).
The pressure sensor is the low pressure cutoff, the high pressure cutoff, and the control for low/high radiator fan speeds.


You have an open field coil on the compressor.....but that shouldn't affect the control (PCM) side of the relay at all.

You say you have no ground from the PCM to turn on the compressor clutch relay ......recheck after erasing fault codes and recheck with the engine running.....



Next, scanner stuff.
Note: My scanner will do these things, IDK if or which aftermarket scanners may be comparable

At this point I want to see the PCM live operating data to see if it is trying to turn on the AC clutch relay or not. (AC request status)

I want to force the PCM to turn on the clutch relay just to make sure it is able to do so (where applicable, through scanner bi-directional controls----I don't want to go looking for wiring problems if the PCM isn't even trying to turn it on for some reason)

I want to see if the AC request is being made from the HVAC panel when it should not be. If HVAC is off, there should be no AC request seen by the PCM.
(You could unplug the wiring from the HVAC panel to eliminate the AC request, if you think it is stuck on)

I want to know exactly what the PCM thinks the AC pressure sensor value is in PSI, because if it's value is excessive the PCM can and will shut off the compressor clutch relay.



Clutch relay is a known issue.
Clutch and coil are known to have their own problems.
HVAC control panel is known to leave the AC turned on through an internal fault, eventhough the panel looks like it's turned completely off.

kwkenuf

Thanks. Headed back out to the garage to recheck with engine running. no check engine light but I will scan for codes. Any value to resetting the PCM at this point?

ezone

Depends on what you find. Erase codes once you know what they are.

kwkenuf

Halfway through steps above (flaky scan tool)..
But on a positive note..... sort of...

With engine on, clutch relay terminal power and ground available regardless of A/C switch position. (abnormal if A/C switch is not selected I expect) This is a change from before when I was doing tests with key on but engine off.

High fans when key on engine off, cuts to low fan with engine on. High fan comes on after long idle warm engine (normal)

Cabin blower motor responds to switch (seems normal)

Trying to find a better code scanner...

kwkenuf

I don't have a scanner that will give me a/c request status or refrigerant pressure....
But my second scanner reports no codes.

ezone

Progress!
So the PCM is able to control the clutch relay normally, and if the field coil were actually good then the compressor would be able to engage and run, correct?

I assume you searched enough to find a couple threads with details about replacing the clutch and coil on the 8th gen 1.8 engine, with the unit still bolted in the car? Yes it can be a tricky job.

So now it appears you are down to proving the HVAC control panel is at fault for keeping the system running when it's not supposed to......Run the engine.....Pull out the HVAC panel from the dash and unplug it, the AC system (relays for radiator fans and compressor clutch) should then turn off.


If so, then this is narrowed down to finding a good control panel, and fixing the clutch/coil on the compressor.

kwkenuf

I'll pull the panel tonight or tomorrow. In the meantime, I still have the issue of the fans not coming on with the A/C request. They did when I first started on this, but around the time I jumped the refrigerant pressure connector is when the funkiness started and my one problem (clutch coil) morphed into two. Would the A/C panel contribute to that?

kwkenuf

Also, for my clutch coil parts, who is the forum's best Honda parts source? I have time for shipping.

ezone

Oh crap. I thought you said the fans did work.
This is yet another reason I'd want to see what the PCM is thinking and doing, by viewing a live operating data list on my scanner. That can eliminate a whole bunch of potentially expensive guess work. Or at least quickly answer a bunch of questions.







Going back, I see this: "Fans do operate when engine is running but condenser fan motor will shut off with A/C selected."
Both radiator fans must run at the same time no matter which speed is controlled (low or high), so if one quits while the other still runs you still have some sleuthing to do.
If you study a wiring diagram, remember I said there is more than 2 fan relays.....the low speed is accomplished by operating both fan motors in series, high speed is done by powering each fan individually. (Radiator fan relay, condenser fan relay, and the one that switches them to series circuit for low speed is called the 'fan control relay'.)

Is this part of your problem???? I can't tell from here at this point but it would appear to be a problem by itself.
No, the panel only generates a single 'request' to the PCM. The PCM then controls the relays for compressor clutch and fans as it sees fit.
The pressure sensor input goes directly to the PCM, not the HVAC control panel.

kwkenuf

I mispoke... er... mistyped... I went back to the first post and highlighted my erroneous info in red.

I'll put together a more concise description of fan operation:
-Key on, engine off, A/C off, both fans operate high speed. A/C switch on, fans operate at low speed and then switch switch off and on.
-Key on, engine on, A/C off, fans operate low speed. A/C on, fans operate low speed. Engine temp increases, fans operate high speed.

kwkenuf

So it would seem I am missing a request to put the fans in high when A/C is selected. (If I understand this correctly)

Edit: Examining the A/C Pressure Sensor chart under System description, it appears that under "Normal operating pressure" 28-213 psi, fans operate at low speed unless temp exceeds 206F. That seems to be what I have here. I thought I read elsewhere that the fans go to high with A/C selected... Have I been chasing my tail on the fan operation part?

That would leave me the constant A/C request ground at the clutch relay (possible A/C control panel) and the known issue of clutch coil....

Thanks for all the help here BTW. It's good to bounce this stuff off of someone who knows what they're doing...

ezone

Well not quite yet.

When the AC is turned on,
Both fans are always supposed to run while the compressor clutch is engaged.
The fans start out on low speed then switch to high speed when the high side pressure sensor climbs above about 220 (ish) PSI.
Below that pressure the fans switch to low speed.
Fans turn off when compressor clutch cycles off.

When the radiator temp sensor reaches its 206F, the fans run on high speed.
(has a dedicated sensor in the bottom tank of the radiator, ECT2).


These are both weird to me. Fans should not run unless or until at least one of the turn on conditions are met.

Again, I'd love to see what this looks like in a live data list on my scanner, that would answer some of my impossible questions LOL

And unplug the HVAC control panel, see if this quits acting wrong.

This makes me think the HVAC panel is bad, sending AC request all the time. Unplug it and see if the fans turn off. This sounds normal.

kwkenuf

Sorry about what appears to be a Ninja edit to my last post which I was composing after you sent your post (but before I read it) saying the same thing about normal fan operation... Our posts crossed...

ezone

Oh God now I have a headache LOL

kwkenuf

I've been told I have that effect on people....

Tomorrow before I pull the A/C panel I will check that the fans go to high when temp rises above 206F and A/C is selected just to put my mind at ease that I don't have a fan issue...

kwkenuf

Clutch, coil and pulley Honda parts source? I'm assuming junkyards on A/C panel?

Thanks!

ezone

I think you already said they did this in another post. Result should not be different with AC on (since the AC has apparently been stuck on the entire time, right?)

ezone

Plenty of dealerships selling parts online at wholesale prices, with real parts catalogs to search.....here's a few to check out, I'm sure google can find more

hondapartsnow
hondapartscheap
bkhondaparts
hondaautomotiveparts
hondapartsconnection
.com/

Compare (discount above) new vs. used and decide?

www.car-part.com

kwkenuf

Yes, they did go to high at 206F but I am unsure if I had A/C selected or not... I want to see if there is any other weirdness with A/C selected and high temp. Mostly to give me piece of mind that I don't have a fan issue on top of the other 2 items...

kwkenuf

Thanks for the list of vendors! At car-part.com they sure do want a lot for used parts! That makes it easier to decide.... Looking at around $450 delivered for all new with the heater control panel... Wasn't able to find a clutch and coil kit together so I'll order separately and get a few extra shims, nuts and snap rings.... Or did I miss a more complete kit somewhere?

ezone

Honda sells the pulley and clutch plate as one piece (kit or set), the field coil is sold by itself. Each comes with snap rings needed and the clutch set comes with shims. You will end up with leftovers.

You should not need to order extra shims or snap rings unless you plan on losing them.



Control panel....got a you-pull-it yard nearby?