hello guys i got 94 hoda civic with two problems the first is that the car blows a lot of heat thru the vents and i dont know whats wrong the second one is i had the ac recharged and the compressor is not coming on does any body have any ideas i think the rellay is good why is it not coming on and how hard is it too change

 

The temperature slider operates a cable that goes down to a mechanism on the bottom of the heater box. You can see it if you crawl into the driver's side floor (my favorite car repair position) and look in the center of the car near the gas pedal. This operates a pushrod that goes to an air door to select whether the air passes through the heater core or not. Also it drives another cable that goes under the hood to a valve that shuts off the flow of hot coolant through the heater core.

Make sure that the mechanism is moving all the way when you put the lever on full cold. Also make sure the other cable is pushing the valve all the way closed. If necessary, undo the clip that holds the plastic outside of the cable and slide the outside the way it needs to go, then replace the clip.

For compressor not coming on, check that the condenser fan starts when you push the button, also the engine idle should increase slightly, and finally if all is right the compressor comes on.

Fan does not start: Check 15A A/C fuse in underhood fuse box.
Fan starts but idle doesn't increase: unplug pressure switch (on the condenser, undo the electrical plug only do not remove the switch from the car) and check if it is closed circuit. If not, all the refrigerant has leaked out. Will need to find and repair leak, evacuate and recharge. If you don't have the tools to do that have a shop do it.
Fan starts, idle increases, but compressor doesn't engage: Check compressor belt (duh), check if power reaches the compressor wire (if not, bad relay), check compressor coil circuit for continuity (should be 3 or 4 ohms), check clutch gap.

 

Actually, for a 94 Civic, neither the fan nor compressor would work if the refrigerant has leaked out or the pressure switch is bad.

Another possibility is that the fan runs but the idle does not increase. In this case, the ECU could be bad.

 

The diagram I have (Haynes manual so may not be that great, but I though all 5th gens were the same) shows the controls in the car directly drive the condenser fan relay. So the fan will start even with no pressure. The pressure switch interrupts the signal to the ECU if the pressure is no good.

 

What you describe above is the circuit from 6th generation Civics. Here's the circuit diagram taken from the 92-95 Civic service manual:



You know, the manual is called 92-95 but is actually the 92 manual. Did the circuit change with the conversion to R134a, which was 94 I believe?

 

I think the Haynes diagram is from a '95. If it is wired as Ron's diagram shows, it would indeed work as he described: nothing would happen when you push the button if the pressure is low.

 

Conversely, if the diagram is as mk described it from his Haynes manual, then his original description is correct. I might tend to go with the latter, given that the Haynes manual is for a 95 Civic, which may be more similar to a 94 Civic.

 

Hey, I seem to have had a similar problem. My wife's car, same as yours, has had a/c problems since she bought it. I paid about $1400 to get everything replaced. It worked fine for a month or two, and now no cold air. Well, it will blow cool air for a little while, but every time the compressor kicks on, there's a horrible squeal. I've had the tension for the belts checked and its correct. I even put some belt conditioner with no success. I am assuming that the bearings in the compressor are bad and that's causing the squeal. Has anyone replaced just the compressor? If so, how difficult was it? I think I can get a compressor off of ebay for around $150 which is fine as long as I can do the work myself. If anyone has any ideas, I'd really appreciate it.

 

That is actually a completely different problem that should be in a new thread. If the noise were really from inside the compressor it would likely self destruct in a few minutes. With engine off, you should be able to turn the clutch plate by hand (counterclockwise) with little resistance. Maybe the alternator belt or condenser fan is actually the noise?

 

Ah, now that I read the original post again, I realize I should have posted a new thread. Thanks for giving me a direction to go anyway. I'll check those out and go from there.