maverickiz3d

Hey Guys. Have been taking a lot of information off this forum for years, but never really needed to post.

Now I need some help with respect to the A/C in my car. Its a CIVIC EG Sedan, originally carburetor but swapped to D15b dual vtec (aka 3 stage) off an A/T car, but using M/T.

When the a/c is switched on, everything is working except for the idle rpm to increase. The rpm drops from 800-850 to around 400 when a/c is turned on.

This has been the issue since the swap. Please let me know which wire I need to check on the ECU, and let me know its complete connection as to where it needs to be connected, whether its ground wire or positive.

Thanks.

Former User

You need to post the year Civic as it could be a R34a or R12 system.

What continent was your Civic produced for?

maverickiz3d

Its 1994. R134a.

Produced for Asia, Pakistan to be specific. Came only in carburetor here.

Former User

The A/C circuit of PGM-FI Civics connects to the ECU so that, when A/C is turned on, the ECU ramps up the idle speed. If that's not happening, then the ECU may be bad or the IACV needs cleaning. Any CEL codes?

maverickiz3d

My assumption right now is that my wiring guy (the electrician) didn't do a perfect job after the swap.

There was no cel light option in the cluster, and i got one sent from Japan of civic eg6 sir m/t. Wired in the cel light myself. So similarly there may be other things the wiring guy left out since he only promised to successfully start my car after the swap.

Therefore, i think the wire from the ecu isn't even connected where it needs to be. Thats what i want to know as to where the wire from the ecu (a17) goes to, so that i can at least verify the wire(s) is connected.

No cel codes, except for ELD.

Btw, its an honor being helped by the legendary Ronj whose comments i have been reading for long!

Former User

You need two A/C wires to connect to the ECU:
See circuit diagram below for details





Ah shucks.

maverickiz3d

Thats helpful! Now i need to know whether those 2 wires are positive or ground?

And, whether current is passing from ecu to relays or from relays to ecu.

Sorry if thats a weird question.

maverickiz3d

Also, ecu and harness is obd2a.

Blk/red is at a17
Blu/red is at c5

Former User

See circuit diagram.

ECU pin A15 serves as a ground for voltage from the compressor clutch relay.

ECU pin B5 supplies reference voltage to the A/C on/off button to detect when you turn the A/C on. When you do, the ECU ratchets up the idle speed, and also supplies ground at ECU pin A15 after a 2-second delay.

The Blu/Red wire is also hot because it also get voltage from the fan relay.

Former User

Oh, okay. Then you have the correct ECU pins.

maverickiz3d

Got it! Really appreciate the input. Will first trace the connectivity of the wires at those pins at the ecu, then find some wires to test the solution.

Thanks!

oneheadlight

I too lurk here a lot, not much to post when so many things in common are going bad and the fixes are there. I had to jump on here and tell you that my 96 civic was doing the same exact thing yours is. Idle would be fine, but turn the a/c on and rpms would go down to about 280-300rpms, almost stalling! For mine it was a defective IACV (idle air control valve). Cleaning it didn't help, checking the resistance of the 2-pin motor showed it was not within the resistance (around 12ohms) it should be. Replaced the iacv and that fixed it. But you should definitely check the signal wires since you had swapped it out.

frost6

Holy snap I thought it was just me having this problem, thanks for posting this!

maverickiz3d

Given that I got no CEL for IACV, I am hoping it works! Furthermore, the IACV I got is a 3 pin type (from an A/T engine). See attached photo.



So how do I check if this is good (if in case the wiring part is fine)? Can anything go wrong while cleaning?

maverickiz3d

Hey guys. Just to update i had the wiring done today and issue resolved!

Thanks for the help guys, especially @Ronj