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2006 V70 2.5T Brake Pressure Switch and AC Pressure Switch Faults

Help, Advice, Owners' Discussion and DIY Tutorials on Volvo's stylish, distinctive "P2" platform cars.

2001 - 2007 V70
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STSCowboy
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Year and Model: 2006 V70 2.5T
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STSCowboy

2006 V70 2.5T Brake Pressure Switch and AC Pressure Switch Faults

Post by STSCowboy » Wed Oct 16, 2019 9:50 am

My Cruise Control Function is intermittent so my guess is this related to Brake Pressure Switch code I just pulled on the Autel AL629. I just got the scanner last night so it’s the first time I used it and it seems like a nice unit.

Where is the Brake Pressure Switch located and how easy are they to change? What is the function of this switch? I’m assuming it doesn’t trigger the brake lights as they function normally with pedal travel.

It also pulled an AC Pressure Switch Fault. A little background on this. The car is new to me from auction and I knew no history on the car. The AC didn’t work so I took it in for service and found the Freon level to only be at .44 pounds instead of 2.2 pounds. The techs serviced the unit and found no leaks. The pressure on the high side was slightly elevated to them but another shop said that was fine. The AC functioned perfectly was a 40* Temp Drop at the vents from ambient for about 3 days.

I parked the car and the next day the AC was only flowing ambient air through the vents. The AC Clutch is still engaging the compressor so I don’t think I’ve lost pressure and there are no strange noises under the hood like something mechanical has been damaged.

My question is, what does this switch detect is wrong (over/under pressure?) how does it effect the AC System?


2006 V70 2.5T Geartronic Silver Black Leather 131,000 Miles

STSCowboy
Posts: 39
Joined: Sun Oct 06, 2019 1:25 am
Year and Model: 2006 V70 2.5T
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STSCowboy

Re: 2006 V70 2.5T Brake Pressure Switch and AC Pressure Switch Faults

Post by STSCowboy » Wed Oct 16, 2019 10:15 am

Update!

I reset the codes and they didn’t come back but the Cruise Control and AC still don’t work properly.


2006 V70 2.5T Geartronic Silver Black Leather 131,000 Miles

STSCowboy
Posts: 39
Joined: Sun Oct 06, 2019 1:25 am
Year and Model: 2006 V70 2.5T
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STSCowboy

Re: 2006 V70 2.5T Brake Pressure Switch and AC Pressure Switch Faults

Post by STSCowboy » Sat Oct 19, 2019 9:16 pm

Found that the AC Condenser has a small leak that only shows up when the system is pressurized. It holds a vacuum no problem.

I ordered a Nissen Condenser.


2006 V70 2.5T Geartronic Silver Black Leather 131,000 Miles

jimmy57
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Year and Model: 2004 V70R GT, et al
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Re: 2006 V70 2.5T Brake Pressure Switch and AC Pressure Switch Faults

Post by jimmy57 » Sun Oct 20, 2019 9:57 am

I wonder if the code definition is worded wrong. There is a travel sensor on brake booster on all P2 of that year model but only models with DSTC (all wheel stability control with traction control, std is traction control) have two pressure sensors screwed into bottom of master cylinder frt and rear circuits. DSTC also have a 5 wire connector at 2 to 3 o'clock position looking at booster. The travel sensor is aat 8to 9 o'clock with a three wire plug. The travel sensor would keep cruise from working if it is not indicating released brake even when no code is shown. The code sets when the signal is far off or missing but reporting a 10% pedal depressed position will kill cruise but not set a code.
The a/c pressure sensor reports pressure to ECM. The ECM in turn runs fan at proper speed to keep high side pressure in check, kills compressor if pressure is below 36 psi (or thereabout) and kills compressor if pressure goes over 425. The compressor will run and not have enough refrigerant to cool and the pressures will support the ECM running the compressor.



STSCowboy
Posts: 39
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Year and Model: 2006 V70 2.5T
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STSCowboy

Re: 2006 V70 2.5T Brake Pressure Switch and AC Pressure Switch Faults

Post by STSCowboy » Sun Oct 20, 2019 10:22 am

Jimmy,

I had one code that showed Brake Pressure Switch which I cleared and hasn’t come back. Now I’m showing a code for Brake Position. I’m thinking the Brake Position Switch is the fault preventing the Cruise Control to engage. The strange part for me understand (I don’t have a wiring diagram so I’m guessing) is you would think the Brake Position Switch or the Brake Pressure Switch would also control the Brake Light Function but the brake lights operate properly.


2006 V70 2.5T Geartronic Silver Black Leather 131,000 Miles

jimmy57
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Joined: Fri Nov 12, 2010 9:25 am
Year and Model: 2004 V70R GT, et al
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Re: 2006 V70 2.5T Brake Pressure Switch and AC Pressure Switch Faults

Post by jimmy57 » Sun Oct 20, 2019 1:18 pm

Look at the booster and master cylinder to see if it has the 5 wire connector and the two pressure sensors on bottom of master cylinder. The brake pressure sensors have nothing to do with the cruise. The booster position sensor is redundancy to assure the cruise goes off if the brake light switch were to malfunction. If the sensor is detected faulty then the safe action is to cancel cruise function. What are the actual codes?



STSCowboy
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Re: 2006 V70 2.5T Brake Pressure Switch and AC Pressure Switch Faults

Post by STSCowboy » Mon Oct 21, 2019 12:18 am

The fault code is ECM 900C


2006 V70 2.5T Geartronic Silver Black Leather 131,000 Miles

STSCowboy
Posts: 39
Joined: Sun Oct 06, 2019 1:25 am
Year and Model: 2006 V70 2.5T
Location: San Diego
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STSCowboy

Re: 2006 V70 2.5T Brake Pressure Switch and AC Pressure Switch Faults

Post by STSCowboy » Mon Oct 21, 2019 12:19 am

:x Brake Position Sensor Signal Low


2006 V70 2.5T Geartronic Silver Black Leather 131,000 Miles

STSCowboy
Posts: 39
Joined: Sun Oct 06, 2019 1:25 am
Year and Model: 2006 V70 2.5T
Location: San Diego
Has thanked: 0
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STSCowboy

Re: 2006 V70 2.5T Brake Pressure Switch and AC Pressure Switch Faults

Post by STSCowboy » Mon Oct 21, 2019 12:37 pm

Does anyone know what the range in resistance the Brake Position Switch is supposed to read through its length of travel?

I need to troubleshoot the switch and wiring/connectors before I throw parts at it.

Thanks


2006 V70 2.5T Geartronic Silver Black Leather 131,000 Miles

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