Honda AC compressor/clutch question

99 Honda Civic EX: at 162,000 miles the AC compressor locked up and burnt up the belt while my wife was on a long trip. I found a used compressor and installed it and a new belt and introduced new R-134, but at no time did the clutch activate… in other words, the compressor freewheels but does not pump any pressure, and there is no cooling action at the vents in the passenger compartment. The gauge on the R-134 kit does show the system is holding pressure. Is that simply from the can of refrigerant? My Haynes manual says to jumper the wires at the low pressure switch. I did, but still no clutch activation.

Question: how can I make the clutch activate while I recharge the system? I see there are two wires going from the compressor body to the clutch area, one black and one red. If I apply 12V to the red one and battery ground to the black one, would that activate the clutch (if the clutch is OK - who knows, it’s an old used compressor?)?

Thanks for all help and advice. This is my first foray into AC, but if you’ve read this far you knew that already.

Yes, you should be able to run jumper wires to the compressor connection and activate the clutch.
Offhand, I can’t remember details on the low pressure switch or wire color code but I generally jump the terminals on the low pressure switch to activate the compressor until enough refrigerant is present to close the switch and engage the clutch. No idea why yours is not working. I’d have to peruse a schematic. I’ll dig around and see if I can find one.

The pressure showing may be the can itself. That can vary based upon the type of can/gauge setup being used. Is the gauge a numerical one or is one of those with the colored bands? I’m assuming this is one of those single can/attached charging hose setups.

I strongly advise gloves and glasses while working with this. Last weekend I informally offered to help someone who had one of those setups from Wal Mart. Something like 15 bucks for a can of refrigerant with dye in it and a short hose. About 2 seconds after I depressed the nozzle on the can the hose started blowing apart at the service port connector; spraying refrigerant and green dye all over. Refrigerant can be very bad news for exposed skin and much worse news if it hits the eyes.

Anyhoo, I’ll see if I can drum up a schematic as I hate to do anything with wiring without a general idea of how things are laid out and what color wires I’m looking for.

@shanonia: Silly question maybe, but when you replaced the compressor, did you also pull vacuum on the system before introducing the new R134a and also add the proper oil to replace any lost with the compressor change? I doubt this is what is causing your compressor to not engage, but expect poor cooling performance and many more problems in your future if you did not.

I think oblivion is on to something here. If you don’t vacuum down the system…you are just wasting your time adding the refrigerant.

Pull a vacuum? No, I just released whatever was in there (using goggles, gloves, caution) before installing the used compressor. What tools and techniques are used in pulling a vacuum? Maybe there’s a limit to what I can do and diagnose before handing it over to a real repair shop.

Re: electrical I have looked over a wiring diagram, slept on it, and am about to look into those aspects.

Thanks to al!

You are getting ahead of yourself without checking the basics. BEFORE you worry about how much refrigerant you have in the system and or if the pressure sensor switch is working… You FIRST must determine if the Electromag clutch is functioning at all. You can test the Compressor clutch…Directly at the Compressor… Run 12 V to the clutch electro magnet and it should lock up… If it does NOT…then the electromagnet coil has shorted out…a VERY common failure mode on compressor clutches… In fact i just repaired the compressor on my 03’ VW GTi by installing a new electro-mag clutch because mine shorted out… It would not lock up when I applied 12VDC directly to the clutch trigger wires… Until I replaced that…nothing would have the chance to function.

To Test the clutch at the compressor just run power to the wires going to the clutch on the compressor… Because no amount of testing or filling the system will make a bad clutch function again if its fried.

If the clutch does lock up and is functioning…THEN you can begin to worry about evacuating the system…Adding OIL…and Refrigerant…and or trace why voltage is not getting to the clutch… there is a path to all of that which you can easily look up on the net. Pretty simple


Thanks al for your help. Yes, Blackbird, I did put 12V to the clutch and heard/felt it function, so I then looked “upstream” in the wiring diagram and came to the place I might have better began: the 20 volt AC fuse in the underhood box had blown somewhere along the process of the original compressor/clutch locking up. I replaced the fuse, started the engine, the AC came on, etc. I added refrigerant. At some point the pressure on the gauge went into the red zone. I bled some pressure out the high side, then resumed adding refrigerant to the low side and stopped when the gauge showed I was in the green zone.

So the AC is working, for now.

The first can of refrigerant I added contained oil, but I don’t know how much total oil is in the system. I have read the receiver/dryer should be replaced along with the compressor, but have not done so. How important are those considerations?

Is it time to turn it over to a professional? Would a pro be able( at not too much expense) correct the amount of oil, install a new r/d and get it charged up again? So far I have under $100 plus quite a few hours of work invested, which appeals to me with this 16 year old car that is still in great condition. So maybe I just see how it goes, and if in the future it needs newer AC parts I bite the bullet, or not.

I think your system has a much better chance of continuing to run for a long time and not giving you a very expensive repair bill if you bite the bullet and shell out for a professional to properly evacuate and recharge the system. If the A/C system was only briefly exposed to atmosphere, you might be able to get away with not replacing the receiver/dryer. However, you have been circulating whatever air and moisture got into the system when the compressor was changed because you didn’t evacuate it first, so it would be a pretty good idea to replace the dryer.

If you’re planning on getting rid of the car in a year or so, then I suppose you could just see how your luck goes.

Thanks for your advice, oblivion. We’ll decide in a few days how to proceed.

I rummaged through my stuff and late 80s is the most I could find on Hondas.

If the system was not evacuated that can make it more difficult to get it to take a refrigerant charge.

Some equipment rental places will rent out vacuum pumps but around here I think they get about 40-50 bucks a day. That’s pretty pricy and you need the full gauge set in order to use the vacuum pump.

There’s an inexpensive (40 bucks…?) vacuum pump available from Harbor Freight but it requires an air compressor to operate and the full gauge set also. Those air operated vacuum pumps are also annoyingly noisy.

I have replaced hundreds of seized compressors, the air in your system is the least of your problems. A seized compressor, burned clutch and melted clutch coil can result in a blown clutch fuse.

Unfortunately you discovered the blown fuse before flushing the a/c system. When a compressor fails internally the system is polluted with metal debris. Normally the system can be flushed with a solvent and the drier (filter) and orifice tube or expansion valve replaced.

At this point you could flush the system and replace the drier but you really can’t flush the compressor. You can turn the compressor up-side-down to drain the oil from it but it is impossible to completely flush all the contaminants from it. Should this compressor fail be sure to flush the system before the next replacement.

Remanufactured/new compressors come dry or with oil for the entire system. If it comes with oil you must adjust the amount of oil in the replacement compressor or flush the entire system.

Thats true Nevada…Ive seen A/C systems never work again after grenading a compressor… I think tiny fragments of metal clog the orifice tube or worse…

Cast My Vote As It Appears Below.
Don’t Try This At Home!
A Man’s (or Woman’s) Got To Know His (or Her) Limitations.

I appreciate working on one’s own vehicle to save money and learn. I work on our family fleet of cars, doing oil changes, brakes, drivability issues, electrical problems, CEL issues, etcetera.

I’ve added refrigerant to old cars to get colder air. However, I know some of my limitations and replacing components that require evacuating and properly servicing air conditioning is one of them.

Think it’s expensive to hire a pro? It’s more expensive to DIY! You’ll damage something or blow it up. Knowledge and an investment in equipment makes all the difference.

How much is free advice worth? You decide.


I do appreciate all the free advice. You are so right that the seekers of advice have to evaluate it and make own decisions.

The day after I got the system working with the used compressor I took apart the original compressor. The clutch pulley was off kilter, it barely turned, and its solenoid was shorted out. That explains the blown AC fuse. The insides of the compressor and the 80 cc of oil in it were clean and new looking, no metal flakes or the like. So I am confident no debris was introduced into the system when the AC failed.

Before I removed the original compressor I taped over the openings on the used one and cleaned it up. When I turned its clutch the tape over one of the openings burped a little, which gave me hope it was pumping. When removed the original compressor from the car [after carefully letting out the refrigerant] I taped over the openings on the pipes. I don’t know if the used compressor I installed is pristine inside and had its 80 cc of oil, but I think so now that it seems to be working just fine.

If the AC fails again I’ll be armed with this experience - and free advice - to deal with it.

The man at the auto recycler let me take the used compressor to install and try out.[It’s from a 1997 Civic.] He said if it works, come back and pay him $45. That’s top of my to-do list today!