OP
OP
clandr1
Full Access Member
It’s the truth
No A/C, driving me crazy.
- Thread starter clandr1
- Start date
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mikez71
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Right, it looks like the PCM controls +B to the compressor.
Have you tried a new A/C relay yet?
Since it sounds like the shop confirmed PCM is sending the right signal, and jumping the relay also works.
Perhaps when the shop commanded the clutch on with a scanner and it worked, it was a short period of time before the relay could act up?
And so do I. The low pressure cycle switch is nothing more than an input to the HVAC control module. The HVAC control module sees that as one of several inputs to be used in the decision making process.
Exactly what PIDS are you reading and monitoring in real time?
Ambient temperature??
What app are you using? Using an OBDII adapter you can see high pressure reading. It is available as PID 1144 from the PCM. The equation is where it becomes either the raw voltage reading or the pressure in psi, kPa or whatever.
Cabin air temp and low pressure switch status are a bit tricky to get since the HVAC control module does not support mode $22.
nonickatall
Full Access Member
I wrote in another forum:
Here's a short list of how you can check your air conditioning system yourself...
First, you'll need a multimeter.
The most important thing is that the air conditioning system is properly filled.
If it is, the low-pressure and high-pressure sensors must be delivering the correct readings. You can measure this with a multimeter. The low-pressure sensor is located at the back of the engine bay at the dryer cartridge in the low-pressure line and must have continuity when the system is sufficiently filled.
This is the most important thing, because air conditioning systems usually contain too little refrigerant, and then this switch shuts it off.
The high-pressure switch is a bit more difficult to measure, but it's not rocket science either. It shuts off when there is too much refrigerant in the system, which is rarely the case.
The high-pressure sensor is a pressure sensor and delivers different voltages to the control unit. With the engine off and the system properly filled, it should deliver between 1.2 and 1.7 volts. You need to measure the black or blue wire against ground.
If these two conditions are met, then your air conditioning system should be able to be engaged via the climate control unit.
If that's the case, then power is reaching the base of your magnetic clutch relay. You can easily measure this with a multimeter. If that's the case, then power must be reaching the connector at the bottom of the air conditioning compressor. If that's the case, then the magnetic clutch must be engaging.
You can check the magnetic clutch by measuring the resistance. Resistance must be 4 Ohm.
That's how I would proceed logically in your situation. If the system is properly filled and the pressure switches aren't defective, then the system should be enabled, and if your climate control unit isn't defective, then there should be power reaching the magnetic clutch relay.
The diagnosis is not so difficult...
Here's a short list of how you can check your air conditioning system yourself...
First, you'll need a multimeter.
The most important thing is that the air conditioning system is properly filled.
If it is, the low-pressure and high-pressure sensors must be delivering the correct readings. You can measure this with a multimeter. The low-pressure sensor is located at the back of the engine bay at the dryer cartridge in the low-pressure line and must have continuity when the system is sufficiently filled.
This is the most important thing, because air conditioning systems usually contain too little refrigerant, and then this switch shuts it off.
The high-pressure switch is a bit more difficult to measure, but it's not rocket science either. It shuts off when there is too much refrigerant in the system, which is rarely the case.
The high-pressure sensor is a pressure sensor and delivers different voltages to the control unit. With the engine off and the system properly filled, it should deliver between 1.2 and 1.7 volts. You need to measure the black or blue wire against ground.
If these two conditions are met, then your air conditioning system should be able to be engaged via the climate control unit.
If that's the case, then power is reaching the base of your magnetic clutch relay. You can easily measure this with a multimeter. If that's the case, then power must be reaching the connector at the bottom of the air conditioning compressor. If that's the case, then the magnetic clutch must be engaging.
You can check the magnetic clutch by measuring the resistance. Resistance must be 4 Ohm.
That's how I would proceed logically in your situation. If the system is properly filled and the pressure switches aren't defective, then the system should be enabled, and if your climate control unit isn't defective, then there should be power reaching the magnetic clutch relay.
The diagnosis is not so difficult...
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