1998 V70 A/C doesn't work, P1308 P0107 manifold absolute pressure/baro low input

Post by **shiloh51933** » 21 Jul 2017, 16:17

My 1998 V70xc a/c compressor won't engage except briefly when I erase the code the clutch engages. New compressor, accumulator, orifice tube and pressure switch/sensor . Any suggestions please? I also have P1308 accelerator pedal sensor DTC, I'm reading that the pressure sensor, accelerator sensor, map sensor and sensor on a/c compressor are all on same circuit or use same ground. The compressor engages if jumped. The pressure switch/sensor plug is only showing 1.2V, I'm pretty sure it's a 5V reference. My climate control model on dash lights up green when I press A/C button or put on defogger. What I haven't noticed is the orange led's that light up when you start up the car. This is my third P80 chassis and we have a P2, I'm sure that the other Volvo's climate control panel had orange led's that lit up after start up,

Post by **jreed** » 23 Jul 2017, 05:22

Pardon this basic question... did you check that there is a full charge of refrigerant in the AC system?
You mentioned that you're measuring 1.2V on the pressure switch... is that between the two pins on the switch? Or between ground and one of the pins?

Post by **Clemens** » 23 Jul 2017, 06:31

To checkbif low pressure or thw low pressure switch are the culprit you can always disconnect the switch and jump the connectors of the wire. If then the compressor engages and stays on you're low on refrigerant or the switch is bad.
Have you checked the clutch gap?
The 850ies all have orange leds on the ecc as far as I know, but if yours is a v/s 70 (can't fins that in your post) it might be different.

Post by **jimmy57** » 23 Jul 2017, 09:11

Something wrong in the a/c high pressure sensor circuit can give those codes. Unplug the sensor and see if the baro code stays gone. If so the high pressure sensor is the bad guy. You will get a code for the a/c sensor being unplugged.
It is on the receiver drier and that is next to the condenser and is not easy to get to. Probably need to pull front bumper cover to get it.

Post by **shiloh51933** » 24 Jul 2017, 15:00

I'm sorry for lack of info I was typing from my android. Initially I couldn't jump compressor, I have since then replaced compressor, accumulator, hose from accumulator to compressor and orifice tube. I evacuated system, recovered refrigerent and recharged to proper level as per specifications. Now it appears I'm having power source issues, the voltage reading from the 3 pin plug for pressure sensor is 1.2V using chassis as ground and middle pin reads under 1V. The 3pin pressure sensor by low side port is new. Now when I jump compressor it goes on but won't go on by itself. I swapped in a known good ECC unit from my 2000 v70xc but made no difference, it was worth a shot. I'm going outside to check other sensor voltages. What else should I be looking at?

Post by **shiloh51933** » 24 Jul 2017, 15:06

jreed wrote: ↑23 Jul 2017, 05:22 Pardon this basic question... did you check that there is a full charge of refrigerant in the AC system?
You mentioned that you're measuring 1.2V on the pressure switch... is that between the two pins on the switch? Or between ground and one of the pins?

Actually I checked voltage between 2 pins and then a chassis for ground which also was around 1.2V. The middle pin reading was below 1V and I read it should be 12V.
I had just replaced compressor, accumulator, accumulator hose and orifice tube...the 3 pin pressure sensor is also new. The refrigerent was evacuated, recovered then recharged properly. The new compressure will engage when jumped, the old one would'nt engage when jumped, even after proper charge and that's why I replaced old one but now I'm having electrical issue with A/C.

Post by **shiloh51933** » 24 Jul 2017, 15:27

jimmy57 wrote: ↑23 Jul 2017, 09:11 Something wrong in the a/c high pressure sensor circuit can give those codes. Unplug the sensor and see if the baro code stays gone. If so the high pressure sensor is the bad guy. You will get a code for the a/c sensor being unplugged.
It is on the receiver drier and that is next to the condenser and is not easy to get to. Probably need to pull front bumper cover to get it.

Which ones is high pressure sensor? I replaced the 3pin pressure sensor by the low side port, it's right behind passenger side headlight. The voltage readings are 1.2V on outside pin and middle pin reads under 1V.

Post by **jimmy57** » 24 Jul 2017, 16:49

The three pin is the a/c high pressure sensor.
No pin read 5v? One end pin is grd, the other is Vref and the center is signal. The 1V reading you get may be equated to pressure less than 35 or so PSI and then it shuts off compressor for undercharge protection.
I missed that you said you had changed A/C HPS already.
IF you unplug the connector for HS then it should be grd-5v-5v. The signal line is Vref through a high Ohm resistor so open vs short vs OK can be detected. the 5V is so low mA that once plugged into the source it has negligible effect on signal.

Amber lights on CCM is not a certainty depending on the settings selected.

The intake pressure sensor is on the intercooler outlet where plastic pipe to throttle attached. Unplug that as the Generic code you list might be pointing to that. Some generic code readers and Euro cars don't play nice and the OBD-II codes can be confusing. The Vref sources in ECM can be shorted and go low to the other circuits sharing that source point.

Post by **shiloh51933** » 24 Jul 2017, 19:08

jimmy57 wrote: ↑24 Jul 2017, 16:49 The three pin is the a/c high pressure sensor.
No pin read 5v? One end pin is grd, the other is Vref and the center is signal. The 1V reading you get may be equated to pressure less than 35 or so PSI and then it shuts off compressor for undercharge protection.
I missed that you said you had changed A/C HPS already.
IF you unplug the connector for HS then it should be grd-5v-5v. The signal line is Vref through a high Ohm resistor so open vs short vs OK can be detected. the 5V is so low mA that once plugged into the source it has negligible effect on signal.

Amber lights on CCM is not a certainty depending on the settings selected.

The intake pressure sensor is on the intercooler outlet where plastic pipe to throttle attached. Unplug that as the Generic code you list might be pointing to that. Some generic code readers and Euro cars don't play nice and the OBD-II codes can be confusing. The Vref sources in ECM can be shorted and go low to the other circuits sharing that source point.

Thank you.
Intake pressure sensor is next to cooling fan relay up top above can shroud.

Post by **jimmy57** » 24 Jul 2017, 21:45

OK, I'm not paying attention. I reread the entire thing with care and see the 2004 Xc70 isn't the subject here.

98 XC70 has a secondary air system solenoid on shroud brow and uses no MAP sensor. The Baro sensor is light violet and is on a bracket on the RH hood latch. It also uses an acceleration sensor down on subframe below a/c compressor. The accel sensor is the better candidate for assing with the Vref.