Jimi Hondrix

1995 Civic EX coupe. M/T. 140k miles.

Purchased a '95 Civic last Friday and after an hour of driving the compressor no longer engaged. I tried several times for the next hour (long road trip) but, never engaged. A/C worked on two prior test drives of up to 30 minutes each. The cabin temp never got very cold but, not surprising for a 5th (and 6th) gen civic so I wasn't real concerned. Today (didn't drive yesterday) the compressor engaged again and ran okay for the 15 minutes I drove the car.

Seller said he and his friend (HVAC tech) replaced all a/c components except condensor and evaporator. They blew out a/c lines before install. He gave me reciepts of new a/c components. Since the a/c system is closed, if it incurs a leak to a point where pressures are off and the compressor will not engage, is it possible for the compressor to engage again the following day ..as in my car's case?

From what I've read a partially or fully clogged condensor can prevent proper cooling return and cause the compressor to draw to many amps, overheat and trip the compressor's hi temp fail safe switch. Is this correct?
If, the condensor is the issue can it alone be replaced or is more involved?
Also from reading symptoms of failing/failed condenser are:
improper cooling and system not functioning.

mk378

Compressor works after a cold start then doesn't later in the trip is almost certainly the clutch gap. You just need to remove some shims under the clutch plate so it is closer to the pulley. When it is hot under the hood, the electromagnet that pulls the plate in becomes less powerful.

A big reason for complaints of inadequate cooling is that the heater valve doesn't close all the way when the dash control is on full cold. This causes the heater to reheat the air from what may otherwise be a perfectly functioning A/C system. This has a no-cost solution of adjusting the cable on the valve on the firewall.

If after checking that, the cooling is still inadequate, you need to get pressure readings.

94eg!

iTrader: (2)

On the EG, the soldering inside the HVAC control unit goes bad and cracks. On mine this meant pressing the AC button does not actually tell the ECU to switch the compressor on. The switch would still light up, but the signal to the ECU was not being sent. I found if I pushed hard on the button, The compressor would momentarily click on (pressure making the contact), then off when I let go. I bought a new heater control unit, but have yet to install it. There are other options though....

To get mine to work, I pop out the AC button out and jam the pointy end of a wooden bbq skewer above the circuit board inside. The pressure completes the connection when the black switch button is turned on.

A better less ghetto option is to disassemble the unit and re-melt all the contacts on the circuit board inside.

On my CRX, the AC switch went bad due to old grease on the metal contact points within. I had two separate switches with the exact same problem. I'm not sure if the EG button is serviceable like the EF ones were. But if re-soldering doesn't do it, then I would give it a look. On the EF you can dissasemble the actual switch. Then clean the grease out with brake cleaner and a q-tip. Re-apply a thin film of fresh silicone grease (like syl-glyde brake grease) and iit should be good to go.

Jimi Hondrix

Thank you.
I recieved similar info on another site I posted in related to the clutch air gap. That replier posted the following:
Spec:
gap 0.5mm (1/2 mm) +/- 0.15mm
or 0.020", +/- 0.006"

coil resistance about 3 - 3.4 ohms
if it measures open, check if the thermal protector is open

I've read that as well (you mentioned), as the clutch coil gets hotter it becomes less magnetic and an out of spec (too far) air gap will not let the coil pull the clutch.
I will look into adjusting the valve cable as well..very good suggestion. Getting pressure readings this Wednesday.

Jimi Hondrix

Thanks.
During internet searches for the past two days in several threads people had the same issue with switch contacts you described. I will approach that if air gap or pressures are not the issue. I mentioned the possibility of bad solder joints/weak contacts to seller and he said it's never been an issue to this point. Is it difficult to pull the HVAC control unit?

mk378

If the condenser fan always starts when you press the button, the control unit is OK.

94eg!

iTrader: (2)

Pulling the HVAC isn't crazy hard, but turned out to a bit difficult for me since I have the lower audio console (I had to remove it). You have to remove the radio and remove the lower console. There are 3 screws and two plugs. You might be able to do it all through the DIN hole for the radio (not removing the console), but my two plugs were too tight to remove with only one hand. You also have to disconnect both temp-slide cables at their far ends (one in the engine bay on the heater valve, and the other in the passenger footwell on the blend-door mechanism. Then it slides right out.

You may be able to test it though by simply pressing hard on various buttons to see if the compressor momentarily kicks on. That's what mine does.

Jimi Hondrix

Being that I just purchased the car and haven't driven it much since, the only time the compressor and condensor fan didn't engage was after about one hour of use on a road trip. I tried several times afterwards during the drive but, it wouldn't work until the following day..car sat overnight. I drove it twice since turning the a/c off and on with a/c button several times and it worked each time.

Jimi Hondrix

Okay..Thanks.

TheJGB3

Yes the problem is the compressor clutch. I had the exact same issue with my 2000 EX. 1992-00 Civics and Integras all came with the same Sanden compressor (excluding Models which came with a B series motor, like the 99-00 Si that came with a Denso compressor).

Jimi Hondrix

I haven't brought it back to mechanic yet not looked at it myself since the day of purchase. A/C has been working fine since then but, I've only used it for short periods and during cooler Florida days. So, to this point I haven't been able to recreate the issue. Thanks for all the replies and will update after this Friday (mechnic).

Jimi Hondrix

Seller replace heater valve less than a year ago. I found an adjustment procedure (posted by Ron J.) but, I haven't tried it yet.
The a/c belt was loose and intermittently squealing so I tightened it up today. Took it to a mechanic last weak and he checked pressures, then pulled vacuum on it, replaced Freon. He said the high side pressure was erratic at idle..the gauge's needle kept bouncing. He thinks the compressor may be going bad/contaminated even though it has less then 10k miles on it.

Brought it up on another civic site and got this response from one of the brain-trust there:
Hold RPM steady at 2000 for testing. Most compressors don't pump very efficiently when the engine is only idling. Also....needle issue........if the high side service port is located close to the compressor it can show vibrations on the gauge needle especially at idle, it can sense every pulse as the compressor pumps at low speed.
If the service port were located after the condensor in the system , you would not be able to see as much of the rapid needle fluctuation.

I will get a chance this Friday to run the a/c for an hour straight and see if the compressor might shut off. If it does I'll pull over and push on the clutch plate to see if the air gap might be the issue.

mk378

Pulsation is normal with the scroll type compressor. They have a once-around pumping cycle.

If you're going to press on the clutch plate be extremely careful of moving parts. If the condenser fan stops along with the compressor, the problem is likely the controls inside the car not the clutch.

Jimi Hondrix

Since my last reply I tightened the a/c belt (was squealing). Washed condenser fins with HVAC foam and garden hose. Adjusted heater valve (seller replaced a year ago). Infrared thermometer reads 48 degrees on HVAC suction pipe but 60 degrees vent temp. Since tightening belt and vacuum + refill... the compressor hasn't shut off abnormally. Hour long drive today in mid 60's ambient temps and compressor seemed to cycle fine. My feeling is the evaporator core may be dirty and needs cleaning. Any other thoughts on what's causing the temp differences from suction side pipes to cabin vents?

mk378

The compressor cycles based on a temperature sensor in the evaporator. This sensor is pre-set to turn the compressor off when the evaporator core temperature is just above 32 degrees. Overcooling the evaporator so that water freezes on the outside causes the A/C to stop working, because air can't flow through an iced-up evaporator.

If the cycling is occurring, the system thinks that the evaporator is cold enough, and nothing you could do under the hood to improve refrigeration performance will change that. It would just cycle off more, and you'd have the same temperature air from the vents.

So the question is is the evaporator really cold enough, or is the sensor cutting off prematurely? If the evaporator is cold enough, the heater could be reheating the air still. You should check that the heater hoses do not get hot with the dash slider set to full cold.

The evaporator core is almost certainly dirty. You can see part of it by pulling the fan motor or the whole fan box. Removing the evaporator from the car of course requires removing the refrigerant. On an old Civic that has never had it done, it's a good idea to pull the evaporator for a proper cleaning while you have the refrigerant out for some other reason.

94eg!

iTrader: (2)

Along that same wire is the AC pressure switch. It too can turn off the system if the line pressure drops too low or spikes too high.

Jimi Hondrix

Thanks. Great info. The person on the other site I mentioned previously came to the same conclusion: possible evap temp sensor issue.

I did that and heater hose after shut off valve isn't hot when set to full cold

Any way to clean it well without removing it from the car?

Jimi Hondrix

Thanks for the reply. I may not know more concerning the initial symptom until i take a three or four hour drive. I drove an hour to work last night and an 45 minutes home this moring and the compressor cycled on normally the entire time.I iwll ask the seller if he replaced the a/c pressure switch during the initial install or otherwise.

Jimi Hondrix

Well, 80 degrees outside today and a/c compressor wouldn't turn on during my ride home from work. Tried several times still wouldn't engage. Pressed on compressor clutch coil for possible air gap issue and it made no difference. Felt heater pipe between firewall and heater valve and it is very hot with dash slider temp control on max cold. At dead cold I think i am going to disconnect the heater valve and look inside and feel to see exactly when it's fully closed.

I plan on pulling the HVAC control unit and resoldering a few points to rule that out. Possible an intermittent condenser fan?

94eg!

iTrader: (2)

Checking the heater valve is simple. Just put it to max hot and go look at the heater valve and note the lever position. Then swtich it to max cold and note the lever position. It should have moved. If it moved, then at least you know the cable isn't broken. Next you can check the cable adjustment by setting the temp to max cold. Now slip the end of the cable off the heater valve lever and, check to make sure you can't close the valve any further by hand. If you can, then you need to un-clamp the cable sleeve by the valve, and re-clamp it in a different position so the cable will now fully close the valve in that position.

With the heater valve, there is one more problem to check for....sometimes the screw on the lever comes loose and it no longer turn the valve inside. You check this by moving the lever back & forth by hand (with the cable slipped off). When the lever is turned, the screw should turn with it as one solid unit. If the screw stays stationary when the lever is turned, then you know it's come loose and the lever is just flopping around unattached. Get the lever keyed in place and snug down that screw.

BTW: Any problem with the water valve mentioned above will have zero effect on your compressor switching on or off. But you don't want to pipe heat into your AC stream anyways.

94eg!

iTrader: (2)

I re-read all your posts and I'm leaning toward a bad solder joint on the AC button circuit inside the HVAC control. Especially if it only fails to come on when it's warmer outside. If you were experiencing pressure problems, the unit would still kick on if only for a moment.

If you don't want to remove the AC control to test & replace, there is a relatively simple test you can do. When it's acting up, remove your glove box. Then un-plug the 3-pin connector on the AC thermostat. Now start the engine. If your 95 is the same as my 94, you can use a wire attached anywhere to the body of the car to ground the pin on the wire harness attached to the YEL/WHT wire. Grounding this pin will bypass the AC Thermostat, AC button and Blower Fan signals completely. If the rest of your system is functioning correctly, your AC compressor and condenser fan should immediately switch on.

If the AC still doesn't kick on, you know the AC button, Blower fan switch, and AC thermostat switch are all good. If it does come on, then you know it's one of those 3 items causing your problem.

Jimi Hondrix

I think this may be the issue. I disconnected the cable (working fine) and tried the valve in many positions and warm are still coming the vents. However, to be sure I need to do from cold engine to know for sure or disconnect hoses from heater valve and inspect visually.

Yes.

Jimi Hondrix

Thanks. I will try that tomorrow.

Jimi Hondrix

Tonight (outside temp in mid 60's) my wife and I went to dinner and the compressor engaged and system blew pretty cold for the 15 minutes we were driving

94eg!

iTrader: (2)

FYI: That YEL/WHT wire I mentioned is the signal wire from the ECU. The ECU supplies 5 volts along this wire. In normal operation, the signal wire follows this path....

ECU +5v ---------> Pressure Switch ---------> Thermostat ---------> AC Button ---------> Blower Fan Switch ---------> Ground

For the system to come on, all 4 of those switches have to be functioning correctly, closed, and all the connections between them must be good.

While you are in there trying to ground the YEL/WHT wire, go ahead and make sure it has 5 volts first. If it doesn't then there may be a problem with system pressure (pressure switch is open), a problem with the pressure switch (broken), a problem with the ECU (no 5v supply at that pin) or a problem with the wiring or connections in between.