My p28 (obd1 civic EX) ecu is functional for the most part but is hindering my A/C from working.
After having taken my car to a more than reputable tuning shop, the tech determined that the ecu was bad. He said that the only way to test this is to get a known working ecu and install it into my car to see if this corrects the problem. I installed a friends ecu and it worked fine.

3 questions:

1. Is there any way to fix the ECU that I have?
2. Anybody have the schematics on this ECU?
3. Does anyone have one for sale or know an inexpensive shop that can repair mine, or sell me another?

 

how does the ecu hinder the AC to not work? i dont see how this is possible.

on a side note, i see stock p28 ecus for sale from 100-125 all the time.

krazy

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by krazy &raquo;</TD></TR><TR><TD CLASS="quote">how does the ecu hinder the AC to not work? i dont see how this is possible.

on a side note, i see stock p28 ecus for sale from 100-125 all the time.

krazy</TD></TR></TABLE>

i agree, i don't know how it would leep it from working????
but on a side note, i have a p28 froma 5 speed for sale. $100 shipped. OBRO

 

the ac has nothing to do with the ecu. it just merely gets the power by y motor.. but is not in any way connected to your ecu.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 2camsaam &raquo;</TD></TR><TR><TD CLASS="quote">
1. Is there any way to fix the ECU that I have?
2. Anybody have the schematics on this ECU?
3. Does anyone have one for sale or know an inexpensive shop that can repair mine, or sell me another? </TD></TR></TABLE>

First off, open up your ECU and look closely to see if there are any burn marks on your ECU, showing that a transistor or resistor has burned up. If that's the case, then you can use the same part off of any OBD-1 ECU and replace it.... we did it to 2 OBD-1 ECUs already (P28 and P72) with the fuel injection transistors and it worked perfectly. So it all depends with your ECU.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mingchi69 &raquo;</TD></TR><TR><TD CLASS="quote">the ac has nothing to do with the ecu. it just merely gets the power by y motor.. but is not in any way connected to your ecu. </TD></TR></TABLE>Umm dont post when you dont know **** huh?? Look at a wiring diagram some time and look at pins A15 (a/c comp clutch relay) and B5 (A/C pressure switch).... For you........

 

Repair or buy refurbished if there a problem

AC is conrolled by ECU. Youll want to test the wires going from the Ecu that read this pin to make sure its getting voltage...

 

I sell JDM P28 ECUs.

You might want to check to be sure everything is fine on the ECU. If something is burned, you might save some cash and replace the burned circuit on the ECU.

 

I just took my car in to the elec. shop too, for the same exact problem with a p28 ecu. I have a d16y8 in my 91 hatch, using the same 91 compressor. The ECU is only putting out like 4 volts to the A/C Compressor Clutch Relay. Any ideas on this?!?! Seems like a common problem. I'll tell them to open up the ECU and check for burn marks. Any other ideas?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mingchi69 &raquo;</TD></TR><TR><TD CLASS="quote">the ac has nothing to do with the ecu. it just merely gets the power by y motor.. but is not in any way connected to your ecu. </TD></TR></TABLE>

yes it does, it is obvious that you know nothing about what the ecu controls.

there are some people who can fix ecus, but it may be easier to get a new one.

 

yAAAAAAAAAy!!!!
My a/c is blowing cold as hell now!!! (not the best analogy but it will have to work).
What I did was install a P07 ecu from a DX that had working a/c in the car just to see if this would get my a/c to work. This made the a/c work fine and I also drove with this DX ecu in my EX for a week til got a new P28, during this time I didn't even get a check engine light, although Vtec was not working.

Once, I put the new p28 in the a/c continued to work fine and I also got my vtec back.

Moral of this story:
ECUs play a vital role in successful operational a/c.


Thanks everyone.

 

Congrats.... Now sell me the faulty P28 not for 130 like in the sig either

 

It is connected. I have the same issue. The blue and red wire sends 5v from ecu to pressure switch

 

Good for you.

12 year old thread bump

Don't do that. Ever. Period.