a/c not working need help with codes

FRESH77015 · #1 (**permalink**) 04-27-08, 05:39 PM

Ok so i checked and i got these codes can you please tell me what they mean and how to fix these problems...

1.B0429 - Temperature Control #3 Rear Circuit Range/Performance

2. P1540 - Air Conditioning (A/C) Refrigerant Overpressure - Air Conditioning (A/C) Disabled (how do i release the refrigerant pressure here???)

jjm01 · #2 (**permalink**) 04-28-08, 02:06 AM

B0429 is the actuator for the rear HVAC. Common problem. If you're not concerned with rear HVAC peformance alone, don't worry about it.

As for P1540, you need some pressure readings. Are the fans working? Condenser clean? Was the vehicle recharged with one of those kits? Please provide us with both high side and low side pressure readings, and the ambient temperature they were taken at.

It would also help if we knew what kind of vehicle this is, year, model, mileage, etc.

FRESH77015 · #3 (**permalink**) 04-28-08, 08:12 AM

Oh SORRY Its a 02' Cadillac DHS It has 110,000 miles on it highway miles tho. I took the car to get the pressure read and the guy told me it was ok. Didn't get the readings I went by his word. But I was going to refill the refrigerant bought from autozone the one that comes with the gauge on the refill tube already and when i hooked it up to the refill port it went all the way to the red!! So i think it is overpressured

SO i dont know what to do. He took the reading at a temperature of 75 (ambient). N about the other code the actuator.. How do I go on about fixing that problem there?? Does that mean if i dont fix it the rear a/c wont work??? How do I fix it??

jjm01 · #4 (**permalink**) 04-28-08, 08:04 PM

Were tarrot cards or a crystal ball used to get those "OK" pressure readings? Because without the compressor running - P1540 disabled the compressor - it is not possible to get proper pressure readings.

Those "refill kits" are not at all accurate - they will show "red" on a system nearly empty with the compressor off. Using those kits often results in four figure repair bills, when the compressor, condenser, accumulator, lines, OT, and sometimes even evaporator all need to be replaced, particularly when sealers, conditioners, and other "enhancements" are added.

If you're not sure of the refrigerant charge, the entire charge should be recovered, system vacuumed down, and recharged to spec. The refrigerant should also be tested with an analyzer.

B0429 will not affect HVAC system performance for the front, only the rear. Depending on the failure you could get constant heat, constant cooling, or anything in between from the rear vents. But the failure will not prevent A/C compressor engagement.

FRESH77015 · #5 (**permalink**) 04-28-08, 09:49 PM

Ok so i was trying to figure out what is wrong with the a/c system. Today in the morning i check the on board diagnostics and come to find out that code P1540 went into history therefore letting me clear the code resulting in letting the compressor engage again. BUT!! As soon as i set foot on the accelerator the a/c stops blowing cold?? N code P1540 goes into current. Why is that?? If i turn the car off and on again the code will go into history once again n will let me clear it again. But you know what happens if i set foot on the accelerator =[ should i take the car to an auto electrician? Is it something electrical?? Or should i take it to an experienced a/c technician???? Please help me!!!!!!!

jjm01 · #6 (**permalink**) 04-29-08, 12:42 PM

It is highly unlikely P1540 is electrical, unless the pressure switch (located on the discharge line) is completely out of whack.

The pressure switch is likely doing its job, it's sensing excessively high pressure which sets code P1540 resulting in the compressor being disabled. Pressing the accelerator of course increases engine RPM's which increases compressor RPM's which increases pressure.

When you clear the codes and the compressor engages, are the fans running? If the fans aren't running, high side pressures will increase in short order, resulting in code P1540.

If fan operation is correct, the system could be way overcharged, the condenser or discharge line restricted. There could also be excessive oil in the system, or air or contaminated refrigerant. That's why we need pressure readings for a proper diagnosis.

If any sealers or conditioners were added to the system, put a fork in it, it's probably done now.

As for the questions in your other post... to kill three other birds with one stone:

B3832 typically sets after the battery is disconnected. Cycle the windows up and down a few times, then clear the code. If the code returns, there is a problem.

B0429 is for the actuator for the rear HVAC. As mentioned previously, it's a common problem (almost always the actuator) and if you're not too concerned with rear HVAC performance you can leave it be. Do a forum search B0429 on this code for tips and tricks on getting to it because the shop manual I believe specifies removing the dash to get at it.

B1586 is a code for the outside memory mirros. Are the mirrors holding the settings? Sometimes cycling the mirrors via the switch to the extremes several times after unpowering the module clears the code, but usually the sensor is bad and repacement is tricky. There's a procedure is the FSM for recalibrating the sensors.

FRESH77015 · #7 (**permalink**) 04-30-08, 08:01 PM

Ok so i took it to a a/c tech/ auto electrician and told me the pressure switch behind the compressor might be faulty. That switch runs about $60 at the dealer he also mentioned that i might as well change the other sensor out since the freon is going to be discharged might as well change all possible faulty sensors... The over all price for these sensors are going to run at about $160 plus $140 hes going to charge me to do the job.. Am I getting a good deal???

carnut · #8 (**permalink**) 05-01-08, 08:19 PM

I think I already answered this post somewhere else. Spend the money to DIAGNOSE it then report back the pressure readings. The reason to replace ALL sensors is for his protection, not yours. NEVER throw parts at a car. Have an expert diagnose it then with that info we might be able to guide you thru the repair. We cannt teach you the fundamentals of A/C repair in 3 posts! The reason the system turns off again after the restart and erasing of the code is there is still a problem. Either no radiator fan operation at the right time or not at all, or the front of the condenser is restricted by debris (bugs, grass, pedestrians etc) or the system has too much freon.

FRESH77015 · #9 (**permalink**) 05-02-08, 07:33 PM

Ok so i got the car back today from the shop. All of the codes went away except for the B1586 Now the a/c kicks in and all but the drivers side will not get cold air!!! Only the passengers side will.. The compressor kicks in at the right times cold a/c but not on the drivers side.. What do you advise me to do..?? I called the dealer but they told me that since the vehicle is close to hitting the 100,000 mark the will not work on it due to that because of the miles it might have some other issues and their rates go a little bit above the $100 mark... So the guy advised me to take it to a qualified a/c tech because its going to be something computerized?? But i wanted to get some advice from you guys first before i make any sudden decisions... Please help me out guys...!!!

777ER · #10 (**permalink**) 08-21-09, 12:43 PM

Quote:

Originally Posted by jjm01

It is highly unlikely P1540 is electrical, unless the pressure switch (located on the discharge line) is completely out of whack.

The pressure switch is likely doing its job, it's sensing excessively high pressure which sets code P1540 resulting in the compressor being disabled. Pressing the accelerator of course increases engine RPM's which increases compressor RPM's which increases pressure.

When you clear the codes and the compressor engages, are the fans running? If the fans aren't running, high side pressures will increase in short order, resulting in code P1540.

If fan operation is correct, the system could be way overcharged, the condenser or discharge line restricted. There could also be excessive oil in the system, or air or contaminated refrigerant. That's why we need pressure readings for a proper diagnosis.

RE: http://www.cadillacforums.com/forums...de-pulled.html (2000 Deville AC problem, code pulled.)

I have the same code but it shows it's CURRENT.

Where is the over pressure switch located on the AC system?

00 Deville · #11 (**permalink**) 08-21-09, 01:34 PM

Quote:

Originally Posted by FRESH77015

Ok so i got the car back today from the shop. All of the codes went away except for the B1586 Now the a/c kicks in and all but the drivers side will not get cold air!!! Only the passengers side will.. The compressor kicks in at the right times cold a/c but not on the drivers side..

The passenger side being warmer than the driver side is a classic symptom of being low on freon in a dual zone system. You need to take it back to the same shop that worked on it and have them add more freon. Have them compare the drivers side vent temperature to the passenger side vent with a thermometer after they add freon.