I have spent a little too much time and money already so I am looking for some help. I am a newby so pls bear with me.

I have a power issue getting power to the AC Clutch. System is charged ad will cool (with a jumper) I have jumped the pressure swith (works) and jumped the relay (works...and replaced the relay too) I have also replaced the Compressor (new). Both the 20 am fuse and the 7.5 under the dash test good. (i have also replaced them)

I believe my limited electrical knowledge points me to the ecu/ecm but need some expert advice. thanks for the help as I am new to the honda tech world.

 

Wow replaced the compressor, huh?? Why?? How much did that run you?? I expertly advise you to take it to an AC shop pay for the diagnosis and then perform the repairs yourself instead of throwing parts at it...

 

I don't have diagrams for a 99, but you might try the other end of the problem. Make sure that the dash controls are asking for AC. Mine is 4th gen and has a separate button and wire that calls for AC.

Also, in my limited model specific knowledge - frequently, there are two pressure switches. One opens at low pressure and the other opens on high pressure. If all else fails, in the old days, we would just run a hot wire to a switch and then to the ac relay and force the ac on. Make sure you are still in line with the pressure switches or you could toast your compressor if your freon level isn't just right.

 

On 4th gen, there is also a diode located next to the AC relay. It is smaller than the relay but still kind of square. When the relay opens to turn off the compressor, there is a kick back surge that this diode stops (to protect the ECU). If the diode is bad it either will not pass any power, or it may have shorted and allowed the kickback to damage the ecu output.

 

same problem help what should i do first?

 

What colour are the power wires for the ac and where can i find them along with the relay your talking about? I cant here it kick in when im turning it on so im thinking its a power issue! any suggestions? Cheers

 

I really don't have the specifics for a 5th gen. You'll have to find a shop manual.... you might be able to download one somewhere, but I don't know where.

Here is some troubleshooting tips - sorry if they are repeats.

In general, the dash controls send a signal to the ECU and the ECU sends a signal through the pressure switches to the AC relay.

Turn key on. You can do this without running the engine, but you'll have to listen for the AC clutch to pick up.

First, It you can jumper the relay and the compressor comes on, then you know the compressor is good. If not, then double check the fuses. You said that you replaced the compressor, so the clutch is most likely OK. If fuses are good, you need to look for a wiring problem from the fuse box to the AC clutch relay.

Second, jumper both pressure switches. (or just the one if that is all there is). If the compressor picks up then the relay is bad.

Third, you can also check to see if you have 12v between the chassis and one of the two sensor wires. If not, then the ECU isn't trying to turn on the AC and we need to look in the dash.

I really don't have any data on the dash controls, so that will need to be researched. The basics are that you want to see a signal coming out of the dash control (probably 12v, but maybe 5v) telling the ECU that either the AC button is pressed or the defroster is on. Sorry I can't be more helpful from this point on.

 

I had a similar AC nightmare recently. After weeks of diagnosis I found 2 problems.

1. When pressed, the A/C switch inside the ac control panel was not supplying the correct signal (ground). I bought a used control panel for cheap and that was resolved.

2. The wire from the A/C thermostat to the ECU was disrupted/shorted. I ran a new wire connecting the 2 to fix this.

I would start by eliminating all things you know are working such as fuses, relays, switches, etc. This will help you zero in on the problem area.

 

ok, I have limited my problem to the fact that the ecu is pushing out a positive signal to the clutch relay and not a negative signal. I have jumped the relay and the clutch relay works. I dont know how to jump the thermostat but I assumed the diagnosis in the honda manual calls for a body ground of the center wire. (this turns the fans on but doesnt turn the ECU to a ground output to the relay.

so I believe my ac thermostat is bad but it may not solve my clutch power issue....

How do I jump the thermostat to ensure the ecu is getting the kick on signal? also how do I check if its a short or a button on my dash thats the issue as mentioned in the previous thread? any help would be great.

 

Not 100% sure since it has been awhile since I had my troubles. But I think the thermostat supplies the ground signal to the ecu, which in turn supplies the ground signal to the compressor+fans.

I think what I did to test it in my case, was hook up a wire straight from the chassis ground to the pin on the ecu (the one that is supposed to be getting the signal from the thermostat) while the a/c button is pressed.

 

lol!!!!

u prolly just need a new climate control.

they are cheap on ebay..

i have this same problem.

but my ac turns on when it wants to..and when it does it stays consistent...

all my electrical stuff is fine. ac charged.
blah blah blah

get a new climate control man. call it a day.