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Hi all,
It got up to 97 in central Florida yesterday and my wife left work in the early evening. The A/C was working fine on our 07 Odyssey when she left, but called me about 10 minutes after she left to say the A/C quit working. I spent about an hour trying to troubleshoot it last night.
First thing I did was put a 134a gauge on the low line with the engine off and it read ~70psi which proves it has refrigerant. I then started the van and noticed the clutch was not activating hence the compressor was not coming on. I checked the underhood and cabin fuse, and both checked out to be fine. Next I swapped the compressor relay with the fan relay, but still the clutch would not activate.
Is there some way to test clutch itself or where do I start to test if power is getting to the clutch itself? I have the shop manual which does list the steps to test the coil to the clutch, but I am hoping there is something easier that can be done to isolate where the problem is.
Thanks
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Just did a bit more troubleshooting. I pulled the relay for the clutch and jumpered pins 1 and 2, but the compressor clutch did not click on. Also the voltage to the relay is not happening either. The condenser relay clicks and shows voltage when the AC is on though. Looking for suggestions on what to check next.
Check for 12v at the compressor connector.
http://www.ericthecarguy.com/faq/solving-automotive-hvac-problems
Since there is no power at the relay, is that worth checking? Although, jumping the pins should have resulted in the compressor coming on if there is 12v there. I will jack it up and pull the wheel and check the voltage, but my guess is that there is no voltage there.
Took the tire off and removed the plastic cover but determined that there is no way I am going to be able to check the power at the connector to the compressor without a lift. If find it odd that jumping at the relay location still did not get the compressor clutch to engage, hence no power to the compressor. But what would explain no power to compressor and no power to the relay? As stated the other two relays (fan and condenser fan) get power and the condenser fan energizes when I turn the A/C on.
Does the pressure switch cut power to both? Could it be a computer problem?
Power on the load side of the relay comes from the under hood fuse box, fuse #12, 7.5A. Power to the control side of the relay comes from under dash fuse box, fuse #30, 10A. The relay control ground comes from PCM, after all the correct conditions are met from the sensors and switches (pressure switch, ambient air temp, cabin air temp, thermistor, etc. depending on trim level and option packages). If you do not have power to the load side of the relay, the control side is probably fine, which rules out the computer. It controls the ground, not the 12v.
Thanks cap, I pulled up the wiring diagram and according to it, if the pressure sensor is open, then the condenser fan should not be on either. I pulled #12 again and swapped it with another 7.5 just to be sure. Still no voltage to the relay. I am still perplexed why jumping pins 1 and 2 on the relay did not make the clutch engage, as this is all the relay is doing. I tested my jumper on the condenser fan relay socket and it did indeed make the condenser fan come on whether or not the AC was on.
Here is what I know:
1) Both #12 under the hood and #30 in the cabin have 12.93v.
2) The condenser fan comes on eliminating the pressure valve as the issue.
3) There is no power getting to relay for the A/C clutch.
4) Jumping the relay socket pins 1 and 2 does not cause the clutch to engage which it should if the compressor is getting 12v.So I am looking for something that would cut the power from #12 to the relay and the power to the compressor assuming that my tests and assumptions are valid. The dangerous part is that these are “my” assumptions based on my limited knowledge of troubleshooting this. I am fairly certain though that it is electrical in nature.
Applying a jumper wire from battery positive terminal to the load side output of the relay should make the compressor kick on. This is important just to verify that the compressor does indeed run (that the clutch is still good).
What trim level is your car? LX? EX? The next thought I had was that perhaps the A/C switch inside has melted or become damaged. This is a fairly common issue on some vehicles (not necessarily yours), and will prevent the 12v from being forwarded from the switch to the rest of the system. Also the thermistor will cut power to the A/C compressor relay in order to protect the system (evaporator, specifically) against freeze-ups. If the thermistor has gone bad (less likely than the switch) it could also interrupt power to the relay. I would check the switch next. Make sure 12v is going into and coming out of it.
Cap, this is an EX-L with RES and NAV. If it were the switch or thermistor would you expect the condenser fan to work? Also, there is power to #12, so would either of these still allow power to #12? I ruled out power from one of the fuses by checking the hot end of #30 int he cabin and #12 under the hood.
Not necessarily, depends on the vehicle. On some the condenser fan works at all times when A/C is on. In other vehicles the fan only comes on when the high side of the compressor reaches a certain pressure (the relay will have 12v applied but the fan won’t run until the control circuit switches the ground on). With the option package in your vehicle, many of the mechanical switches have been replaced with touch screen and electronic modules, so the difficulty troubleshooting this increases by an order of magnitude. To check the fuses properly, you need to visually inspect for intact filament, burnt contact, or other physical damage, and then check voltage at power side and at load side. The nav, body controller, and PCM, however, control the ground side of the system. There should be nothing preventing 12v from getting to the fuses and being passed on from the fuses to the relays other than wiring faults. With that said, I am assuming you are checking for 12v against a known good ground. If you are attempting to check for 12v against a controlled ground, then you would not see the 12v if the control is bad. Check for the presence of 12v against a known good ground, such as neg battery terminal, engine, frame, or exposed metal on body.
Checking the voltage against a good ground, it has voltage. So, does the clutch and the relay share a ground? I have a feeling this will be going in the shop on Tuesday 🙁
If the A/C relay has voltage on its load side, and you short the load side terminals and the compressor does not kick on, there is an issue with the compressor clutch or wiring, as the compressor clutch gets it ground at the engine. Taking it to the shop at this point may not be a bad idea, especially considering the amount of electronics installed that you wouldn’t want to damage during more invasive electrical troubleshooting. Let us know what happens.
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