Hi all,
My a/c went out a few months ago and now that summer is starting already in Texas I figure it's time to fix it. I think it's a ECU issue but what do you guys think.

First thing first, I followed the instructions in the helms manual and also the Honda service manual and everything passes, yet my a/c clutch will not engag. I can jump the relay then it engages so it's not a clutch issue. But to be safe I replaced it anyway since I have a lifetime warranty on it. Along with the drier/expansion valve/ evaporator but still not working.

I checked every wire in the a/c and didn't find any breaks. I read a thread on here that I should be getting about 5v from number c5 wire on the ECU? I'm only getting about .3v. I've also noticed that when I select my A/C button on, that my engine RPM does not increase. Could it be that my ECU doesn't know the button is pushed in to increase the rpm and give those 5v out of c5? I looked up the wiring diagram and can't find the wire that sends true signal to increase the rpm when the A/C button is selected. I ordered a ECU from eBay and should arrive in a few days.

Any idea?? Thanks!

 

Redo this test. If you unplug ECU connector A and turn key to ON(II), you should measure battery voltage to body ground at the Blk/Red wire pin A17 in the connector.

Also, you didn't mention whether the condenser fan runs when you press the A/C button..

 

Yes the condenser fan turns on when the a/c button is pressed. Also with connector A still plugged in I am getting battery voltage at 17. Does it have to be unplugged? That red/black wire runs to the pressure switch which I am getting battery voltage on the other side of the switch.

 

0.3V at A17 is not battery voltage.

Wrong.

A Blu/Red wire runs between the pressure switch and ECU pin C5.

A Blk/Red wire runs between the clutch relay and ECU pin A17.

 

Got my numbers/colors mixed up. Let me double check but I sure I was getting 12V from 17 and only .3v from c5 with the pressure switch unplugged

 

 

Yes I am getting battery voltage at A17 with the connector plugged in and also unplugged

 

betting or getting?

If you ground pin A17 with key in ON(II), does the clutch engage?

Did you retest voltage at the Blu/Red pin of the unplugged pressure switch connector?

 

If I ground pin A17 the clutch does engage. And I rechecked the voltage on the blu/red connector of the pressure switch and I'm only getting .18v or (.05v with connector A unplugged from the ECU)

 

Unplug the pressure switch and ECU connector C.

With key OFF, test the Blu/Red wire for continuity and for continuity to body ground.

 

I checked the blue/red wire from the pressure switch to the C5 connector and it shows continuity. How do I check it for continuity to the ground? According to the diagram it's not grounded anywhere?

 

Good.

Set multimeter to read continuity.

Touch one meter probe to pin C5 in the ECU connector and the other probe to the metal frame under the dash.

 

There is no continuity

 

Your original hunch was correct. Buy a replacement ECU.

 

Thanks for your help RonJ. It should arrive by Thursday and I'll let you know if it works or not

 

If the ECU you bought is good, your A/C will work again.

 

Also should I be worried that my rpm doesn't rise when I select the a/c or is that because of my faulty ECU?

 

This^