lurice01

My ac does not work on my 95 civic ex sohc vtec obd1, the fan and condenser neither will turn.

I first would like to get the fan running, correct?

Fuse #35 under hood is good and Fuse #13 under dash are OK.

I disconnected the condenser fan relay 4P connector. and connected the WHT and BLU/BLK wires with a jumper wire (on the wire harnessed side, like in the service manual pg 22-7) and the fan did not run. to do that i just took one piece of wire and put one end in the WHT and the other end in the BLU/BLK...ok?

I disconnected the jumper wire and using my multimeter set on DC 20, i found no voltage between the WHT wire terminal on the condenser fan relay 4P connector by placing the red multimeter line on the WHT, and the black multimeter line to ground. It read zero

SO that means there is an open in the white wire between the under the hood fuse box and the condenser fan relay harness thing? So i took a harness from my junk civic and its testing the same. everything same. no changes with a new ac harness. So i guess the problem is further up closer to the fuse box?

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I continued with the other condenser fan tests for the heck of it:

i did next step = disconnected the 2P connector at the condenser fan.

Next service manual says to check for continuity in the BLU/BLK wire between the condenser fan relay and fan. That is confusing. I can do continuity on multimeter (and i have this other device that lights up i guess when there is continuity)... What i did was test from BLU/BLK terminal at 2p connector at the condenser fan, and the only thing that would produce a tone is if i connected the other multimeter line to the WHT terminal at the condenser fan relay 4p connector. So i believe there is continuity?

Finally, I tested the condenser fan motor by running wire from the fans 2P connector directly to the battery. The fan ran! so i started the car with fan running and turned the ac on but the compressor does not turn when observed.

So since the fan ran, Manual says i should repair open in the BLK wire between the condenser fan motor and body ground. If wire is OK check for poor ground at G751, And also way over by passenger side headlight, where the ac systems entire wire harness connects, a ground wire comes splits out and is grounded to the passenger fender wall frame area... and its like that on both civics. I cleaned that real good and got it shiny metal to metal and fan still wont work. Had this car running strong since 2003 and AC has never worked but the light has always came on at the Climate Control and the Fans Blow.

mk378

Is the pressure switch (on the condenser) closed? I think on that model if there is no pressure the fan will not start either. The light on the A/C button does always come on even if there is no pressure.

Do you have power to the fan relay? The fan and the compressor are on the same underhood fuse. When both don't work you should double-check the fuse. Also pull the fuse and look at the contacts in the fuse box for signs of melting.

Former User

Test installed 20A hood fuse 35 for voltage like this:

https://honda-tech.com/honda-civic-d...fuses-3079359/

lurice01

@RonJ I used the fuse testing method you posted and the under hood 20amp condenser fan fuse is the only one that will not read. It just says zero, the rest say almost 12 so that's something.

@mk378. Under the fuses i see no signs of melting or anything. Is the ac compessor pressure switch the 2p connecter near fan with BLU/RED wire and YELLOW/WHT wire?

Former User

Replace the hood fuse box.

lurice01

@RonJ I replaced the under the hood fuse box with one from my junk civic, then the fan worked and I am truly grateful.
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So I continued to troubleshooting the compressor..

I double checked fuse #13 in dash fuse box & the 20 amp condenser fan fuse #35 under hood fuse using the method. They read all like solid 12.

I went behind glove box and disconnected the A/C thermostat 2P connecter however mine was a 3P connector and i'm sure its the right one, and i read elsewhere that is ok and to ignore the black yellow wire during testing...

I connected the two terminals using a jumper wire but wire was a paper clip (other jumper wire i have was too thick and the paper clip works when im jumping for check engine light)

Then i started the engine and the compressor did Not engage.
so i turned the ignition off and reconnected the a/c thermostat 2/3p connector.

Then i went under the hood and disconnected the compressor clutch relay 4p connector and measured the voltage between the WHT wire terminal on the harness and body ground and it was solid 12v.

Then i turned the ignition on to II. and measured the voltage at the BLK/YEL terminal and body ground the same way and it also read 12v. then i turned the ignition to OFF.

THen i tested the compressor clutch relay by putting a wire from car battery negative to top right terminal of relay, another wire from car battery positive to bottom right terminal, i heard it click, then i tested for continuity between top left terminal and bottom left terminal and their was continuity tone. That means its OK.

Then i disconnected the compressor clutch 1P red wire connector. Service Manual says to Check for continuity in the RED wire between the compressor clutch relay and compressor clutch. That confuses me. Can anyone explain how to do this step or did i miss something before this point?
Also, looking ahead some troubleshooting mentions use of an ECU test harness, do i need one or is there a way around that?

mk378

Measure resistance through the whole compressor from the clutch wire to ground. Should be 3 or 4 ohms. You can also jump the wire to the battery with the ENGINE OFF and the clutch should pull in. Do not jump the compressor with the engine running, since that bypasses the pressure switch it can over pressure.

lurice01

Ok i put multimeter red probe on the 1p compressor red wire connector and black multimeter to ground withit set on 200ohm scale and it read 3.5.

I also heard and saw clutch engaged when i jumped same red wire to battery.

I'm grateful but still need help

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I don't have the tool to check the clearance of pulley and pressure plate at the moment ...

Checking resistance at field coil and its 3.5 on the 200 ohm scale of multimeter. That means its ok.

Says to reconnect ac compressor clutch relay

Then connect ecu test harness n I don't have that. Its to see if i need to repair BLK/RED wire between compressor clutch relay and ecu. And/Or the BLU/RED wire between condenser fan relay and ecu.

If they're ok i must replace ecu. I have one from junk civic should i try it or did i miss something?? Thanks

I don't have test har

Former User

There's no Wht wire connected to the clutch relay. Do you mean terminal 2?



If you unplug ECU connector A, and then ground pin A17 (Blk/Red wire) with the key in ON(II), does the compressor clutch engage (click)?

lurice01

Hmmm i mean if im looking at terminal with the connecting clip facing up, i tested the top right terminal, 92-95 civic service manual says WHT on page 22-9

About to try the ecu test

Former User

Dagnabbit, I thought you had a 98 Civic.

Ground pin A15 (Blk/Red wire) not A17.

lurice01

that's Ok. So I disconnected harness A from ECU. Then i ran a wire from my battery's ground and touched other end to pin a15 on the ECU harness by BLK/RED wire. I did this with key on II. And the compressor did click and move.

Next I tried to ground the B5 pin also. It was a Blue/Red wire i believe. I did so with the ignition OFF and nothing happened. Did i do this test correctly? Do i need to repair that wire? If not, the ECU must be bad?

mk378

OK let me get this first. Everything plugged in, you start the engine turn the heater fan on and press the A/C button, and the condenser fan starts but the compressor does not. Correct?

The engine must be started and running at a normal rpm before the ECU will pass the A/C command through from the blue-red wire to the black-red. Note that this is negative logic. When the A/C is supposed to be on, the blue-red will drop from 12 volts to near zero volts. Measure this at the ECU with everything plugged in.

If the engine is running at normal rpm, the blue-red wire is near zero volts, and the ECU still does not pull the black-red wire down to engage the compressor relay, ECU is bad.

Former User

^This result may indicate a bad ECU. See next test below.

In terms of ECU function, ECU pin B5 supplies a reference voltage to the A/C button. When you press the A/C button ON, the ECU B5 voltage gets grounded, signaling the ECU to supply ground to ECU pin A15, which activates the clutch relay and in turn causes the clutch to engage.

The test I recommend that you do next is to unplug both the condenser fan relay and the pressure switch, and then measure voltage at the Blu/Red wire in the pressure switch connector with the key in ON(II). Post the voltage reading.

lurice01

@RonJ The BLU/RED wire on the 2p connecter read 4.7v with the key on II. I also had the condenser fan relay disconnected like you said.

(I also still have the condenser's 1p red wire disconnected AND i also still have the little compressor clutch field coil disconnected because the service manual did not say to reconnect them.)

@MK357 I can also read voltage at BLU/RED wire on B connector at ECU harness, but should key be on II or OFF?

mk378

Plug everything in. Start engine and turn on A/C. Confirm that the condenser fan runs but the compressor does not.

Measure voltage on the blu-red wire at the ECU. It should be near zero with the A/C on and go up to battery voltage when you release the A/C button. When you press the button and the ECU sees that low voltage, the ECU should rev the engine slightly off of idle then about 1/2 second later pull in the compressor relay.

Former User

This finding^ together with the previous one showing that the compressor clutch engages when the A15 ECU wire is grounded strongly suggests the ECU is bad.

lurice01

OK folks I'm just going to go ahead and install this ECU I have from my junk civic but will it work in this civic or what details need to be the same?

The junk civic is a red 1995 Honda Civic EX. with a D16Z6 engine. It has Vtec but the valve cover doesn't say Vtec... but i see the little round cap of vtec solenoid thing on side of engine, and D16Z6 are VTEC, correct? It is made in the USA.

My car that needs a new ECU is the exact same as junk car except its made in Canada and currently has a D16A vtec engine and has a valve cover that says vtec. Before the D16A it had possibly a D16Z6 in there.

Former User

Should be fine for testing purposes.

lurice01

Hey sorry for the delay. I installed that ecu from my junk civic, started car and compressor still not spinning.

I re-did all the tests except field coil (I'm sure it's same)

and plate clearance check I don't have tools to do but i can watch it and see it doesn't move when i press a/c button but i see it move when i jump the red 1p wire to the battery.

I even grounded the a15 blk red wire from harness side of ecu again, and the clutch clicked/engaged. Should i be grounding the pin on the ecu and not the harness side..?
I guess both of the ecu's could have bad a/c?

Remember the thermostat test, how my 2p connector is a 3p instead? Maybe i have to test it differently??

Maybe I swapped the little clutch and fan relay boxes because i had them off a few times... Would that effect anything?? I'm lost

Former User

Don't give up on the idea of a bad ECU yet.

Aside from the A15 grounding test that worked as expected, be specific and give details about the other tests you redid with the ecu from the junk civic installed.

mk378

Everything plugged in, start engine and watch the voltage on the blu/red wire at the ECU as you push the A/C button on and off.

lurice01

I checked fuse #13 7.5 amp under dash and #35 20 amp under hood using the method and they were 12 amps.

I went under glove box and disconnected the 2p thermostat connector. But mine is 3p: it has a blue/red wire, a yellow/white wire, and a black/yellow wire. I jumped/connected the blue/red wire and the yellow/white wire on the dangling harness. then i started the engine. And the cimpressor did Not engage. I turned on a/c and compressor still did not engage. I tried jumping with paperclip and real wire. I turn off engine and reconnect 2p connector....

I go under hood and I disconnect 4p clutch compressor relay connector and get 12v reading at white wite on harness. I turn key to II and get 12v reading at black/yellow wire on same connector. I turn ignition switch off....

I tested the clutch relay by connecting it to car battery and listening for click, then listening for continuity tone on the other two terminals. I did this on my spare two relays also and tried all three, they all test good but none make the clutch engage...

I disconnect the compressor red wire 1p connector and test the compressors red wires continuity and it's 3.5 at the tip.

The next step i have not done. Check for clearance between the clutch pulley and pressure plate. How do i do this?? What tool do i need??

mk378

Voltage with button not pressed: _____ volts
Voltage with button pressed: _____ volts

lurice01

To do this test, after i start the engine do i disconnect the b harness at the ecu? Wont the engine shut off? I see the blue/red wire but can't start engine with it's harness disconnected

Or do i not disconnect it and stick one of those t-pin things in there and test from it maybe?