Model: Civic Hybrid
Engine Size: 1.3L
Refrigerant Type: R134
Experienced Honda tech spent 1.5 hours on it and is stumped. Here's the background and facts.
- Compressor can be commanded on by jumping 1-2 pins on relay. Clutch kicks in and blows cold.
- All fuses and relays tested
- Continuity through thermal protector
- Coil resistance test passed (if coil was problem, clutch wouldn't engage right?)
- A/C system does not respond to on/off control from cabin
- Climate control self-test pass
Note: The A/C originally stopped working because clutch/bearing failed. Clutch and bearing replaced, confirmed working, but A/C won't work from control panel.
Would really appreciate any suggestions.
You say when the system was jumped, it cooled. Were low/high side pressures measured during that test (I'm not familiar if the self-test provides that or similar information)? If so, did they appear normal? If not, is there a low or high pressure cutoff switch that could be blocking the request from the controls in the cabin?
I'd be trying to assess refrigerant charge level long before jumping on electronics...
There is a high pressure switch but there's no evidence it isn't working (no codes). Even when it is bypassed the system still doesn't work. I tested the low pressure line to be in range. Can't test the high pressure line. Don't have the gauge for that. Refrigerant charge level was tested by shop. If it was over or under charged wouldn't there be an indication via sensor?
You need a circuit diagram, from the older Honda's, blower switch must be making contact and has a diode to activate a relay, capillary tube used to be a switch, not a thermistor running into an AC amplifier. This evaporator temperature device was the main control for cycling the compressor switches on above 39*F, off at below 33*F. Then a dual function switch in the side line, had to be closed if the pressures were between 40-430 psi, more than likely a thermistor now feeding the AC amplifier as they use to call it.
All this stuff was in series, if all okay, would energize the clutch relay. Just saying a tad more than just the clutch relay. Get an alldata.com circuit.
If you have automatic climate control. even a lot more complicated.
Edited: Thu July 18, 2013 at 5:45 PM by NickD
The non-hybrids pass the A/C command through a Multiplex Control Unit to the ECU. It's basic negative logic, the control panel pulls a wire low, it passes through the pressure switch, and in some cases the thermal protector, then on to the MCU which transmits a coded signal to the ECU. The ECU then closes the compressor relay.
The main test is to check the voltage at the pressure switch (from either lead to ground), it should switch from 5 or 12 volts to near ground when the A/C button is pressed. If it is a 3 wire sensor not a two wire switch the system is entirely different.
Compressor is driven by serp belt only. I've read where some HCHII's have a combo belt/electric motor driven compressor. I can say with certainty there is only power source for my compressor.
The safe mode theory is a good one but I would think there would be some code(s) to indicate such. No?
As for the problem being caused by some component or system unique to the hybrid , I am not aware that the A/C system on the hybrid is any different than a regular civic.
I stand corrected. The compressor is also hybrid powered, by the engine serp belt and electric driven via an internal electric motor in the compressor. The big orange power cable coming out of the right side of the compressor led to the 'a ha' moment yesterday. Sorry, I'm new to auto mechanics (although I'm becoming well informed on A/C systems trying to solve this fricken problem!!).
I still feel the issue is electrical/electronic. It really feels as though some sensor is malfunctioning but not causing an ECU fault.
I lurk in a Ford Escape Hybrid forum but own a gas version. You might be better off going to a Honda Civic Hybrid forum for operation questions. Lots of Hybrid owners use a Scanguage II which can show lots of vital battery pack info. I know of one FEH owner that has three of them daisy chained together!
Dang it...lost my post. This darn computer is so 'touchy'.....
A word of caution. Hybrids are not vehicles to begin or continue 'OJT' training. These vehicle require specific diagnostic procedures and test that require specific tools to accomplish. The compressor used on this vehicle should be scroll unit, however, it does have a belt driven section and also a electrical motor part. The belt driven part...12 volts..no problem...the electrical motor part uses a 200 volt motor for compressor operation. Now we are talking an entire new program. A suggestion would be to obtain the correct diagnostic flow chart for your vehicle. This maybe available thru All DATA on a single purchase/single user program. Check ALLDATA web site for info.
It is felt that the problem with the clutch is an electrical problem and is more than likely a sensor issue. However, it is almost impossible to determine which sensor or group of sensors without the correct info and tools. The use of a scan tool maybe require to completely evaluate the system and test/activate sensors. A good multi-meter rated for at least 600 volts is also a good addition to the tool box. Class '0' gloves are also a good investment....protects the fingers...arms....heart....heck all of the body. Should be tested prior to each use. Make sure there is no leakage (holes) in the gloves. Be careful with these vehicles...they can be very dangerous to the uninformed technician.
Service of the compressor requires specific lubricants and service procedures. Insure that the system is clean and there is no possibility of introduction of PAG oil into the system. PAG is detrimental to the motor windings in the compressor and may result in internal damage to the unit. Contaminate lubricant should be removed (totally) from the system. Have read several on line post that this is not a serious issue and the "OE's" are simply attempting to 'scare' people into using the dealers. Not sure....but if what is expressed by the "OE's" is the least bit true....why take the chance. It is known that these vehicle represent serious concerns for EMT/First Responders because of the voltage/amps of the electrical systems. Since we are typically putting our hands directly into the mouth of the lion....take the appropriate protection measures.
Most 'OE's' will allow for app. 2-3 hours (billable) for a diagnosis of these systems....from that aspect...it appears these new systems can be quite complicated. Take the time...use the correct tools to insure a positive outcome.
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