Vehicle: ’97 Accord EX, 5sp, 143K mi. I’m coming to a dead-end; help me solve this & I'll buyyou a pizza & 6-pack! Summary: AC has worked 100% fine for years until a few weeks ago. The dash AC light illuminates but the compressor doesn’t kick in. Here’s what I’ve done: Started with checking all the fuses in the driver footwell and near the passenger firewall. All good. Next, I checked the two relays (one for the compressor and the other for the electric fan) located forward of the compressor near the driver-side radiator fan. Both function when removed and tested, but I did not detect any input voltage that would close the AC relay circuit.

With the engine running, I put a jumper wire in place of the AC relay, and the compressor kicked in, put a load on the engine and AC blew cold air (quick 15-20 second test), so it seems to work OK. I put that AC relay back and then put a jumper wire on the low pressure switch to see if that was the culprit. No luck.

After more reading, thought I might check the pressure with an auto store AC recharge kit (kind of a mickey-mouse setup…) Followed the instructions which mostly collaborated with the Haynes manual. Said the compressor had to be running to charge, so I put the jumper wire back in place of the AC relay & tried to do the charge (gauge did read low). Can of refrigerant didn’t seem to do much; didn’t hear anything going in system & weight felt the same. The compressor, however, seemed to put more and more of a load on the engine until the engine nearly died (orig idle RMP about 800). I pulled jumper wire off & engine returned to normal idle. While manually revving the engine a little higher (1350?) I put the jumper back in place and the compressor loadkilled the engine!

And that’s where I am. I put the relays back in place and the car runs fine, but I’m back at square 1: No AC. Hope I didn’t jack the compressor! Got any ideas? Like I said, if you can help solve it, you got yourself a pizza and 6-pack on me!
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1997 Accord EX, 4Dr
4 Cyl. VTec, 5sp, 143K mi.


[IMG]local://upfiles/9275/C130F253357548348B118627D5BC5D9D.jpg[/IMG]

 

the reason why engine might die when ompressor engages could be
# 1 system overcharged
# 2 compressor starting to lock up ..
# 3 ECM , not recognizing the a/c on input to boost idle up ( very unlikely )

Now let's roll our sleeves up and fix this thing
You say that when you jump the relay compressor comes on .. this is what i want you to check
at the compressor relay there are 4 wires ( white, red, blk/yellow, red/blue ) start the car and turn a/c system on , get a volt meter or a test lite and chk for power at the white and yellow/black wires,, they both should have power,,
also chk for ground at the red/blue wire , if either is not present compressor will not work ..
If no power at either the white or yellow/black wire could be a bad fuse ( # 8 , under dash fuse box 7.5 amps or fuse # 34 , 15 amps under hood fuse box ...or wiring problem ,
If you get no ground at the red/blue wire ,, then it is a bit more complicated than that ,,,
If you get no ground , disconnect the connector at the a/c pressure switch ( 2 wires ,, blue/yellow and red/ white.. chk to see if you get ground at the blue /yellow ..
If you do .. reconnect the connector , with it connected see if you get ground at the red/white ,, if you do not you got a bad pressure switch
If you DO NOT get ground at the blue/yellow, ground the red/white wire and see if compressor turns on ...

try these tests and report the results

 

Thanks much for outlining the tests. I did them, and here are the results. To first summarize, I never did get a ground at the red/blue wire at the AC Relay thru any of the tests.

Also, to define "ground", I used test leads and a 12V LED, connecting the positive side of the LED to the battery, and the negative side of the LED to whatever ground I was trying to test (see images 1&2). One thing I did notice was that although the LED did not light up when testing the red/blue, my volt meter sometimes showed continuity between it and the engine (see images 3&4). Just thought this piece of info may help.

-- Illustrations at http://www.nigelspearlnecklace.com/accordac/--

Test results of the AC Relay...
With the engine off, ignition off-
White - has power (LED on when +lead to white wire, -lead to -car battery)
Red - has ground (LED on when +lead to +car battery, -lead to red wire)
Blk/yel - no power, but it does act as a ground. (LED on when +lead to +car battery, -lead to blk/yel wire)
Red/blu - nothing; no power, no ground (but sometimes has continuity - see pics)

Ignition on, but engine not running-
White - has power
Red - has ground
Blk/yel - Now has power
Red/blu - still nothing; no power, no ground

Engine running, Dashboard AC switch on-
All wires have the exact results as above when the ignition switch is on

AC Pressure Switch...
Engine off, ignition off-
blu/yel - no ground
red/wht - no ground

Ignition on, both engine off or on-
blu/yel - Now has ground
red/wht - no ground

Used test leads to connect these wires & test the pressure switch. LED on (see images 5&6) so pressure switch works. So it seems like we can eliminate the pressure switch(?) Then this made me wonder if the dashboard AC switch is what completes is ground circuit for the red/blue wire on the AC relay? Maybe it's a bad switch? This red/blue wire is where I never saw a true ground, just continuity sometimes. Seems like when red/blue gets ground, the relay should close to connect white/red, and thus the engage the compressor(?)

With the ignition/engine off, I quickly jumpered the white & red, and I heard what I assume is the clutch engaging in the compressor. And I checked the relay again to ensure it works, and I could hear it closing/opening. Well, thoughts? And BTW, really appreciate your help; would love to get this solved!

 

Ok,, we are almost there..
if there is no ground , car running a/c on, at the blue/yellow at the pressure swtich , the red/white won't have any ground either,, red/white is on the output side of the switch..

Now what i need you to do , is to locate the a/c thermostatic switch , it is located under the dash rt side , on evaporator, you need to remove the glove box ,, it has 3 wires ( blue/red, blue/yellow and black/yellow, ) car running a/c on,blower motor fan on, , chk to see if you get ground at the blue/red... If you do not you got a problem ground circuit heater control panel.
if you get ground at the blue/red, see if you get ground at the blue /yellow.. If you do and there was no ground at the same wire at the pressure switch there is an open in that wire
If you DO NOT get ground at the blue/yellow and you got ground at the blue/red.. you got a BAD thermostatic switch,, need to remove the evap to replace it ,,, try something.. leave connector at thermostatic switch unplugged , suppply a ground to the blue/yellow and see if a/c turns on ,, make sure everything else in the system is plugged in

let me know

 

I've done all the tests, and everything checks out OK:

A/C Thermostatic switch on theevaporator -
[ul][*]Both blue/red and blue/yellow had ground when turning the A/C on[/ul]
A/C Pressure Switch -
[ul][*]Checked the pressure switchagain, and it hascontinuity.[*]I also checked the blue/yellow at thepressure switch plug again, and it has ground whenA/C button & fan are on.[/ul]
I also pulled these files and I'm afraid the next step is having the dealer check the ECM. On the flow chart, everything passes up to the point where it directs to put on the test harness (which of course I don't have). Also, looking at the Circuit Diagram (see at link below), the red/blue from the A/C relay connects to the ECM. I'm narrowing on that wire again since it is the wire where I never see a ground. I connected that A/C relay to the plug via test leads. With the engine running,I supplied a ground to the red/blue wire and the compressor kicked in asit should and the A/C began to cool.

So, what do you think? Is it time to have the shop put on the test harness and/or check out my ECM? Again, your input certainly appreciated and valued.

These are the diagrams I followed:
http://www.nigelspearlnecklace.com/accordac2/