greg51

I am seeking help to troubleshoot why A/C compressor clutch will not engage on my '99 Civic DX.

Here's what I've done so far and if you can take me to the next step. This is my 1st Honda I have ever owned or worked on.

Bought car a few weeks ago and A/C did not work. Compressor would kick on when I jumpered the low pressure switch. Found hole in condensor where someone hit a curb or something. System not pressuized. Replaced condensor last week. Not knowing any better, I added a can for R134. Should have evacuated system. Compressor engaged and A/C started working while I added R134. Not great but working for that day. Drove civic next day and compressor would not engage. Low side pressure 70 psig. High side little over 100 psig.

Started with usual checks again. With engine running and A/C on there is voltage at the compressor (does not engage) and condensor fan runs. Low pressure switch read continuity. Blue/white wire on connector does not ready 12/14 volts. Previously it had voltage week ago. Jumper across connector and clutch does not engage. Compressor thermal switch measure continuity. Feil coilds measure zero ohms where your other post stated 3 to 3.35 ohms. Clutch rotates with little clearance. Did not measure gap since I can hear it lightly rub the pulley when it rotates.


Started looking for a short. Found I had trapped wire bundle between condensor and frame. Thought, A Ha, thats it. Got wires out. Inspected. No wires showing they were grounding to frame. Clutch still did not engage. Followed wire bundle back to a connector mounted in front of battery tray. Measure continuity from this connector to low pressure connector. Continuity was good.

I have read where you and others mention the ECU or I guess its the PCM because I don't see ECU in my Haynes manual. Recommends grounding terminal A15 or B5. I am unfamiliar with where to find these connectors or terminals. Checked passenger side under dash and found a brown multi-pin connector but no numbers on it. There must be another conector somewhere.

In my fumblings, I shorted the black/yellow lead at the A/C thermostat and no longer get 12/14 volts on that terminal. Checked all fuses. under driver dash and under hood. All good.


On Monday I plan to have the refrigerant recovered, system evacuated and recharged with refrigerant and oil.

Thanks for any and all help you can provide.

Former User

Problem #1: This^ is a must eventually, but first sort out the electrical problems below.


Problem #2: Repeat the coil test. If it reproducibly reads 0 Ohms, then it is bad and is one reason that the compressor clutch fails to engage.

Problem #3: All of these issues are possibly explained by a blown 7.5A dash fuse 17. Turn the key to ON(II) and test whether the installed fuse has voltage to body ground at both top test tabs.

greg51

Ok, got it. I won't touch the R134 until I solve the electrical problems.

My mulitmeter died the other day and I pulled out my old Simpson analog multimeter (thinking it was bullet proof from the '60's) and it was giving me the zero ohms on the fiel coil. I didn't want to beleive it. It did not read battery voltage correctly either, so I'll head to sears and buy a meter.

When I removed the fuse from slot 17 it did not look blown but to be certain it was good, I placed 1 ear on the battery and the other ear to a test light that lit. I suspect I won't have power at the 2 top test tabs in slot 17.

Kinda frustrated with the A/C right now so I'm gonna take a small break today and wash and wax my Audi tt. It needs those light scratches buffed out.

Thanks for sharing your knowledge and experience RonJ@HT

greg51

Borrowed a cheap meter from a neighbor. Fiel coil still measures no resistance at all. Indicates its open. Range set to 200 ohms on meter. Shorting leads, meter reads ohms in the teens.

Slot 17 in fuse panel. Removed 7.5 amp fuse. Measured continuity across fues ears. Switched meter to 20 volt range. Measured zero volts at upper terminal of slot 17.

Got tt bathed and waxed. Looks great. Damn the humidy of the Ohio Valley.

Former User

Did you calculate the actual coil resistance by subtracting the meter internal resistance (teens Ohms) from the coil reading?

Does the meter have a lower scale, such as 20 Ohms. If so, redo the resistance measurement on that scale.

Was the key in ON(II)? What did you measure at the lower slot? You can more easily do the voltage tests with the fuse installed using the two top test tabs.

greg51

My mistake. Prior voltage readings at slot 17 were with ignition off.

This AM and using a test light, ignition on, slot 17 upper terminal no light. Lower terminal test light on. Will still buy a VOM later today.

Former User

Also test voltage at installed 20A hood fuse 56, and redo your tests below with the key in ON(II).

Currently, does the condenser fan run when the A/C is turned on?

greg51

Ok, got a decent VOM. Please disregard measurements I quoted on original post since my Simpson meter highly questionable, except continuity, maybe.

I started car and turned on A/C. Condensor fan came on. Idle rose for a moment and settled back to normal.

Slot 17 upper terminal 0 volts, lower terminal 14 volts.

Moved to A/C thermostat under dash and unplugged 3 wire connector and measured Blk/Yel 14 v, Blu/Red .02 v, Blu/Wht 14 v. Plugged in connector and measured Blk/Yel 14 v, Blu/Red .25 v, Blu/Wht .26 v.

Moved to Fuse box under dash. Cooling Fan 20 A fuse measured 0 v on right terminal, 14 v om left terminal. Condensor Fan 20 A fuse measured 0 v on right terminal, 14 v om left terminal.

Moved to Lo Pressure switch and measured .25 v on Blu/Wht wire, 4.7 v on Blu/Red wire.

Moved to compressor and unplugged Red wire after the Thermal Switch measured 14 v.

Turned off ignition switch and returned to under the hood.

Measured continuity across Lo Pressure Switch. Still have R134 pressure.
Measured continuity across the Thermal Switch
Measured continuity across the Red wire to the Field Coils and Black wire coming from Field Coils. Readiing does not flucuate in any way, blink, nothing even when scraping the probe across compressor body or valve cover.

So the Field coil is likely bad, but I think I need higher voltage at the Blu/Wht wire of Low Pressure switch. Where can I go from here?

Former User

Was the pressure switch unplugged, engine off, and the key in ON(II) for this measurement?

If the coil were good, you would also measure continuity in this test. What was the actual resistance reading with key off?

The fact that the compressor gets battery voltage but the clutch does not engage is a clear sign that something is wrong with the clutch mechanism. If the coil resistance is out of spec, then it's bad. Make sure to also measure the clutch clearance.

greg51

My post reads sequencially, so car was on during all voltage checks. Car was off during resistance checks.

Response to Q1 - Lo P switch unplugged, car running, A/C button & key ON(II). Turned key ON and A/C button on, engine not running, unplugged Low P switch connector. Blu/Wht wire .21 volts, Blu/Red wire 4.71 volts. About same as engine running condition.

Response to Q2 - The multimeter LCD display does not show a resistance value. It never moves from the default display when turned on. A 1 shows in the left side of display. It is a total 4 digit display. If I cross the leads the display reads 000.2 ohms. Lowest ohm range is 200 and thats position used.

Response to Q3 - Clutch to pulley clearance is about .035" It spins freely and light rubbing.

Clutch mechanism engaged a week ago Friday, May 27. Its possible it broke that Friday with only an hour or 2 of running. Field coil is curious. Replace bot or coil only? Not even sure they are available. I'll check locally see what I turn up.

greg51

Autozone $107, 2 -3 day shipping to store for P/U.

Former User

The voltage at the Blu/Red wire should be around 5V, so your 4.7V reading is fine.

Voltage at the Blu/Wht wire should be battery voltage (~12.5V). The reason that your reading is low is because you have the A/C button turned on, which grounds the voltage thereby lowering it. Had you turned the A/C button off, the voltage would jump to about 12.5V.

The coil is clearly bad (has an open) and needs to be replaced. Replace it and your A/C will work again.

The clutch gap is too wide. It should be 0.02" +/- 0.006". Install a smaller shim to bring the gap to spec.

You need to replace the coil and shim. The OEM coil costs ~$62 and a shim costs ~$2 at Majestic Honda. This does not include shipping and handling, which would probably cost about $15.

greg51

Ok, I will recheck Lo P switch voltage of Blu/Wht wire with A/C button off.

Proabably go the Autozone route and reset gap with new kit. Guess this used car I bought had a few things on the edge. A/C was one of several mechanicals I have repaired due to basicly neglect. I'll post my success this weekend, hopefully. Going to be a full court press to finish by Sunday.

Former User

Just a minor side note, the A/C pressure switch is both a high and low pressure switch not just a low pressure switch.

greg51

Can I just remove compressor belt. Loosen pulley nut by using strap wrench on pulley. Remove 4 compressor mounting bolts. Lower compressor enough to use 2/3 jaw puller to remove pulley. Will I have enought clearance to do this hanging from the hoses?

Thanks for sharing your knowledge.

Former User

If you understandably wish to avoid disconnecting the A/C lines, I believe you need to remove the compressor belt and mounting bolts and hang the compressor from some rope. This should allow you to move the compressor around enough to access the pulley with a two-jaw puller.

greg51

Alright. Found a compressor clutch kit at a local store and had some real kinda fun taking the old clutch plate & pulley off. Got the new clutch/Coil/pulley kit installed. Took a little while to get the clutch plate gap to .020".

With all things done, turned on key to II position. Checked 14 volts at pressure switch Blu/Wht wire. Wiring checks complete though I forgot to measure the field coil before installing. May still do it when its light out.

Started engine and turned on A/C button. Clutch did not engage because the R134 leaked off. Jumpered the pressure switch and clutch engaged.

LIFE IS GOOD ! ! ! ! YESSSS

I suspected R134 would be low because when I started removing the power steering pump, I leaned my hand on the Low Pressure side hose at runs along top of condensor and it started hissing. Got some wrenches and tightend.

Once can was running I put a gage on Low P side. Zero pressure. DIs-assembled flalow P side fitting and found o-ring cut. Replaced o-ring and tightened fitting. Ready to head to A/C shop tomorrow for R134 evact, oil and recharge. Hope all goes well.

This Warsteiners's for you Ron. Thanks a helluva lot for the help.

greg51

Auto Shop evacuated system and perform pressure test. No leaks. Charged with R134. System working as designed.

Former User