Thundar

I searched but did not see another thread so...

A/C compressor and fans are running continuously, regardless of whether the A/C switch (on the heater control unit) is on or off.

fans come on when key is on, also Compressor is not cycling

New compressor and charged, with 12 oz can will add the other 2-3 oz once get fixed.

Checked compressor relay with another one no help, fans still run when no relay in compressor does not, so not relay.

read else were could be ground issue or bad HCU?

I'm thinking bad HCU but my questions on bad HCU would that keep compressor from cycling or just keep AC on like button was on? If it doesn't control the cycling what should I check next? Thanks

ezone

Even with the entire system turned off, blower turned off?
(AC is supposed to operate while in defrost mode, without the AC light....but if the fan is turned off the entire system is supposed to shut off.)

Remove and unplug the HVAC control panel in the dash. If that gets the AC compressor and fans to shut off, replace that control panel.

Thundar

Yes even with fan off on HCU (fan under dash stops but not compressor and rad/condes fans) and did the defroster hack trick... So does the HCU control compressor cycles that's my biggest concern right now does not cycle ever always running have to unplug the compress to keep it from blowing line or icing.

ezone

What happened when you unplugged the HVAC control panel?

Thundar

=It did stop both, so going with HCU being problem. Will get a new or used one, but still did not answer question does that HCU control were it makes the compressor run all time? I will find out and report back but yes no asking for 4 times asking would be nice. y/n if HCU controls the compressor cycle... And got car police auction so have no way to get radio code how to find that did not unplug this time, but need to seems get to remove replace hcu? got post?

Edit: saying thanks another there is seller on ebay has heu for cheap new oem on panel but has warm mirrors for cheap, is same wire as button as defrosted can go with that one>? seems like would use same stuff, other wise will go with used one.
For others maybe post to tell, sure is cheap no one knows its same thing other thing than pic if it is.

Thanks for help;

ezone

Ok.......

The HVAC control panel sends an "AC request signal" to the PCM, the PCM then controls the compressor and fans as long as it thinks it's ok to do so.

The HVAC control panel controls compressor cycling based on evap core temp sensor input.....but when the control panel is bad ('ac request' stuck on) it may run the AC regardless of core temp input.



https://radio-navicode.honda.com/

Thundar

cOOL that is answer wanted will report back once get new HCU installed, hope it fixes it. I think what we talked about it will.

Side note can't you get some code from radio code that will give info before I unplug it for that site? That site in past have not giving correct codes in past.

ezone

Yea...sometimes I really don't feel like typing out a long explanation. Sometimes it's much easier to give short answers like "just unplug the damn thing" or "don't ask why, just do it"
Then I get called an a55h0le.
LOL

Follow the link, every step should be explained in that site.

Also.....you may need to register as the new owner of that car with Honda.....the site may not give you the radio code if you aren't registered as the current owner of that VIN on their files. You can call the customer service number to do this if you wish, and they might then give you the radio unlock code over the phone if you have the 8 digit serial number for it.

Thundar

Been reg on that site with many Hondas before, just don't want to get locked out this one... I'm new to 8ths gen done tons of fixing 92 up just new to this new 8th never know with these computers controls everything what will break... Ezone thanks for help your the best!

From other site took longer but same answer so Ezone doesn't have to type it out:

The A/C clutch relay is directly controlled by the HCU/HVAC control module in the dash, and not by the ECU/PCM module. So yes, that is possible and very probably at this point - read on for details.

The main fans (radiator and A/C Condenser fans) are controlled by the ECU/PCM which is told (from various inputs such as coolant temp) and via network data from the HCU how (low speed/high speed/off) and when to operate the fans. In addition, and this part has nothing to do with your issue, the ECU/PCU can tell the HCU not to engage the A/C clutch relay if certain input conditions occur (such as if the AC pressure switch reads outside its nominal operational range, again via network data.

In your case it does sound like the module is malfunctioning, its energizing the A/C clutch relay and also telling the ECU/PCM to crank up the radiator and A/C condenser fans to operate in high speed mode.

To check, I'd unplug the HCU with the car off and then start it up, at this point (assuming the car is cool) the rad and A/C condenser fans should be off, the A/C clutch should not be engaged.

Hope helps anyone else that has same problem... they should do recall on these damn controls!

Thundar

Well that fixed it with a used for $35 09 HCU all good now, more info those looking that I did not know at time:

FWIW, this happens because the HCU/Climate Control Unit outputs an 'always on signal'.

It can happen to:
06 1.8l and 2.0l coupe (uses the sedan HCU)
06-early 09 1.8l and 2.0l sedans
06-early 09 Hybrid
06-early 09 CSX

07-11 coupe HCU do not work in the 06 coupes or 06-11 sedans.

Honda/Acura sells revised circuit boards to fix this issue.

If purchasing a used HCU/Climate Control Unit it should come from late 09-11 models. These already have the revised circuit board.

Used HCU/Climate Control Unit store codes even after they've been disconnected from power so be sure to clear them.

HCU DTC clear:
1.Turn the ignition switch OFF.

2.Set fan control dial OFF, temperature control dial on MAX COOL.

3.Press and hold the ventilation and recirculation control buttons, turn the ignition switch ON (II).

4.Ventilation indicator turns on for 2 seconds, then DTC clear.

Climate Control DTC clear (Hybrid and CSX)
1.Turn the ignition switch OFF.

2.Press and hold the AUTO and windshield defrost buttons, turn the ignition switch ON (II).

3.Windshield defrost indicator blinks for 5 seconds, then DTCs clear.

ezone

Gotta nit pick this claim, it's incorrect info for your car. If you locate factory wiring diagrams, you could see how this is set up.

The PCM controls the relays for the compressor clutch and the radiator fans.

The HVAC control unit only sends a request signal to the PCM.

This method allows the PCM to have final say over whether or not to allow the AC to run.
This is handy info, thanks!

Thundar

I would agree didn't know what was ventilation button is it or which to push but maybe on euro model? Just posted cause maybe could help someone that got used HCU may help. Glad got 2009 version with new stuff inside hehe.

ezone

Maybe, Recirculate?

Thundar

3.Press and hold the ventilation and recirculation control buttons, turn the ignition switch ON (II).

so no what is vent? all good for me but next that might needs help?

ezone

Just got a chance to look in some service info, I did not find the same info you posted

....for an 08 USA Civic there is no memory erase procedure listed....... it says HVAC fault codes are automatically cleared when the problem is resolved.