Hi, My Accord is stuck in A/C! As soon as the key is turned on, both fans and the a/c clutch are engaged as if the switch is pushed in calling for a/c. When the a/c switch is pushed in, it lights up but does not change anything. It is not stuck and it feels normal. I have checked the relays under the hood in the fuse/relay box and they are all working normally. They are being told to come on as normal. If I unplud the low pressure switch in the accumulator everything turns off as it should. Does anyone have any ideas what I could try next?

 

When you turn on the A/C switch, you ground a wire to activate your a/c. Somewhere your wire is grounded at all times before the pressure switch.

If your setup is similar to my 95, then the only two components downstream from the pressure switch are the thermostat, a stuck a/c switch on your console, or a grounded wire.

The Online Manuals link the DIY section have a 98-02 accord shop manual that will help. Use a continuity setting on a volt meter to ensure that the wire is grounded. Verify that one of the wires is grounded at the pressure switch (blu/yel on my accord your may be different).

Unplug a/c switch and see if wire is grounded (or start car and see if a/c turns on immediately). Do the same at the thermostat (on top evaporator in my car).

 

Okay, I spent most of the day checking stuff and here's what I found:
With everything set to "off", when ya turn the key to the on possition, both fans turn on and the a/c clutch engages. after start up, the a/c clutch is engage, and both fans are still runnung. with in a few minutes the low-side line from the evap starts to ice over! if you push in the a/c switch and turn the blower switch to any speed the a/c switch lights up and the clutch dis-engages and the fans all stop(unless the engine is hot and calling for cooling). I have removed the a/c controls from the dash bezel and found that if you unplug it, the fans/cluth behave like normal. I disassembled the a/c controls and found the switch working normal. It rang out w/meter fine. I traced the GRN/YEL wire from the a/c control to the low pres. switch and back to the ECM and it is fine-no damage or shorts. So I think the control unit my be kaput. But I was wondering if anyone else has any thoughts on this. Or maybe(hopefully) I just missed something. Where would be a good place to buy a new/used control unit?

 

I just looked at the 98-02 shop manual that you can download from the DIY section.

The hot side of the a/c switch is the blu/wht wire. If you have the control unit removed, see if that wire is grounded with the a/c switch unplugged. The ground label is G401 and the green wire goes to that. It is under the center console. See if that ground is loose or there is corrosion on it. I put some pics of what I am talking about below.

 

I checked the blu/wht wire from the connector and it is not grounded(with the heater control unit unplugged). I found G401 and all the wires are fine. Thanks for the pics. I also checked the 2 diodes located in the pass.side fuse panel and they are fine. they only read in one direction. I am at a loss for what to check now. Hasn't anyone ever had this kind of problem before? I am wondering why everything works fine untill the heater control unit is plugged in, then the fans & clutch become energized. I got a headache now!

p.s. I looked for the repair manual you spoke of, couldn't find it. can you tell me the link? I found files for everything but a 1998 accord.

Thank you!
Ronski

 

The link is spoonertuner[dot]com We aren't supposed to post the actual link.

Click on manuals link

You want:

Accord 1998-2000 ESM CD ISO server 254 MB

Its an iso file, so you will have to burn it to a CD.

Test the two leads on the a/c switch that correspond to blu/wht and the green wire.

The circuit on the switch should be open when switch is off and closed when the switch is closed.

 

Thanks for the link- it worked great! I took the HCU apart and the switch works with my meter, but I can't figure out which leads on the HCU connector corespond with them... I spent about 4 hour messing around with it tonight. What I found was kinda wierd! With the connectors plugged into the back of the HCU(heater control unit) and the key on, I get 2.2volts on the YEL/GRN wire which is the "A/C on output" lead. when you turn on the fan and push in the a/c button it jumps up to 3.9 volts. Now heres where it gets wierd- if you unplug the HCU you get 4.4 volts on the YEL/GRN wire with the key on! I followed this all the way thru the a/c press. sw. and back to the PCM BLU/RED wire! WTF! Does the PCM send a signal to the A/C on switch? I am using a Fluke 32 and I am very confident of my readings. I thought the signal went FROM the HCU through the A/C pres. sw. then to the PCM.

Additionally, I completely removed the fuse/relay center under the hood and physically checked each wire from the firewall grommet out to each device and found no pack rat damage or shorts. Tucson is big on wire damage caused by pack rats!

Does it look like I need a new HCU or what!

 

Anyone have an answer? Can someone please check their wire to the accumulator and check the voltage at both wires with the a/c on and with the a/c off. please?
Thanks,
Ronski