Troubleshooting Climatronic

Hello everyone,

I came across this great forum through a link.

Fortunately, my expertise was probably sufficient to be admitted .

I drive a Passat 3B Variant V6 Syncro (first registered in December 1998, 168,000 km). It's a gasoline engine, but I hope that doesn't lead to disqualification.

I've been having a problem with the Climatronic system for over a year.

'Sometimes, the air conditioning simply shuts off. For example, when driving on the highway, everything is fine (code 19 = 0). The cooling performance is very good. However, when driving off the highway and encountering stop-and-go traffic, the system shuts off (code 19 initially shows 1, then 3; according to the documentation, 1 means...).' Behr-Hella indicates high pressure and 3 instances of low pressure, but the pressure sensor does not differentiate between these and instead evaluates the states based on time.
This mainly happens during warm weather (like we're experiencing now).

If you turn off the car and wait, for example, for an hour, then everything usually works perfectly again. Until it all starts over again.

The display occasionally flickers when turning on (so there is a fault). The system's error memory shows '318', but Volkswagen technicians can't make sense of that code. They were also unable to help me at Behr-Hella.

The vehicle's diagnostic system indicates: F129 (pressure sensor). The pressure sensor has been replaced, but the issue persists. The system has been refilled and checked for leaks (apparently it is leak-free). The dryer and expansion valve have also already been replaced. The error is still there:(.

When the system shuts down and the error code is 19=3, a 'ticking' sound can be heard from the area of the compressor. This sound can be easily heard using a screwdriver (to amplify the sound) on the right-hand hose of the air conditioning system (when standing in front of the car and looking at the engine, the two hoses are located on the left side of the splash panel). The left-hand hose does not make this ticking sound. The frequency of the 'ticking' sometimes changes.

Who can help me? Two VW workshops and a specialized climate control company were unable to find the fault.

Greetings.
Peter.

Hmm, difficult.

Based on your description, I suspect the system is shutting down due to overpressure and/or excessive heat. This could be caused by your condenser (located in front of the radiator) having reduced cooling capacity due to dirt buildup, which leads to the system overheating and being unable to cool effectively. The fan control unit should also be checked to ensure that the fans are still working and activating at the correct temperatures.

The knocking sound might be coming from worn compressor bearings. When you turn off the air conditioning, it will probably go away, right? Does the ticking sound change proportionally to the engine speed?

Just another thought... the engine's mass airflow sensor is okay, right? It might be worth replacing the coolant temperature sensor; it's not that expensive. This shuts off the compressor at high temperatures.

Based on the description, I would also suspect insufficient cooling power when the car is stationary. Either the radiator is somehow blocked (pinched from the outside or clogged internally), or the air conditioning fan (if you have two fans in the front) is not turning on or is otherwise defective. When the car is stationary in hot weather and with full cooling capacity, it should eventually turn on. You should check that.

@Julian & Varianti,

Thank you very much for your answers.

The fan for the air conditioner is running. Does it actually have two speeds, or just one, in the 3B model? Which way should the air be blowing?

The reason for the question is that I replaced the fan for the air conditioning system more than a year ago (because the old one was making noise). Perhaps something is connected incorrectly.

I need to have someone check the coolant temperature sensor. It could be the problem. However, there are no error codes stored in the system's memory.

Greetings.
Peter.

Hi,

The fan for the air conditioner is running. Does it actually have two speeds, or just one, in the 3B model? In what direction does the air need to flow?

Well, I think it goes from the outside to the engine compartment, right?
Otherwise, it would.
1. the hot air from the engine compartment flows around the radiator and...
Starting at speeds of 20 km/h, the fan is hardly able to overcome the oncoming airflow.

@Markus H,

Okay, I admit that was a silly thought. But I wanted to explore all the possibilities. In any case, the fan is drawing air into the engine compartment. Everything is fine here.

But is the fan for the air conditioning two-speed?

I'm now almost certain that the climate control system is shutting off due to excessive pressure. The likely cause is either insufficient cooling or the aforementioned coolant temperature switch (where is it located, and how can I test it?).

Now, the only question is what exactly is causing the overheating.

Greetings.
Peter.

HI!

The fan has 2 speeds. Have you checked if the capacitor is clean, or completely covered in dirt and flies?

The coolant temperature sensor is located somewhere in the coolant circuit, near the outlet of the engine block. Unfortunately, I'm not familiar with your vehicle, so someone else might be able to describe it better.
It's difficult to test, as it was also defective in my Golf 4 and provided incorrect values, but nothing could be detected in the speedometer or error memory. The item costs about 15€... I would just exchange it to try it out.

Is there enough engine coolant?

@Julian,

What determines which speed setting the climate control fan is operating on?

Which parameters are relevant?

When should the air conditioning fan be running on the second speed setting?

My suspicion is that a mistake was made when the climate control fan was replaced (over a year ago), and that the fan is only working in the first speed setting. Level loading.

I haven't been able to observe this behavior recently during normal operation. Level loading.

Over the weekend, I let the car idle and, after turning off the automatic climate control, I sprayed water from a hose onto the condenser from the front. After some time, the automatic climate control turned back on , and additionally, the second [component/function] activated. Fan speed .

What could that mean?

Greetings.
Peter.

Hi!

Okay, it depends on what the coolant sensor at the radiator is measuring. Depending on the temperature, the after-run time or the respective stages are controlled. Does the lower hose connecting the water cooler to the engine get hot when the engine is idling?

Then there's a fan control unit that regulates the fans based on generator load, board voltage, and capacitor temperature.

My Passat is at the mechanic's today, at the third one. VW dealers.

There, they really put in a lot of effort .

It seems that the pressure switch (which was replaced first, a year ago) is probably broken.

The second speed setting of the air conditioner is not working. As a result, the pressure increases, and the system shuts down.

Apparently, someone plugged a jumper wire into the workshop instead of the pressure switch, and sure enough, the second stage is working.

They have now ordered a new pressure switch. Let's see.

Although it seems logical, I don't think it is. Or does the pressure switch have different switching states, and is only one of them defective?

The air conditioner is also switched off by a signal (high pressure) from the pressure switch.

Greetings.
Peter.

Hmm, isn't the pressure switch supposed to control the fans? However, I'm not sure about that.

The fans are primarily controlled by the temperature switch on the water cooler. The pressure switch only recognizes pressures that are too high or too low.

Hi,

The pressure switch activates when the system pressure is too high or too low (normally open; first contact pair), AND a second contact pair (normally closed) activates the cooler fan one level higher when the system pressure exceeds 16 bar.
If this switch is no longer working, the pressure will continue to rise through the condenser without additional air until the first pressure switch opens, which will shut off the compressor.

Best regards, Andy.

OK, that sounds logical!

@Andy,

Thank you, great explanation, it looks like you've described my problem exactly .

Are you an expert? Only the third VW factory has come close to the cause, which you are casually describing here on the computer in the forum.

Greetings.
Peter.

HI,
Well, uh, I'm definitely not an expert in the field.
I've had my first air conditioning system in my car for almost 2 years now, and it stopped working about 4 weeks ago.

See here:
Okay, I'm ready. Please provide the German text you want me to translate.

Since it wasn't a simple error, I really dug into the issue (I read VW's self-study programs, analyzed and measured the circuit within the control unit). Then your problem will be quickly explainable...

Good luck.

Andy.

Grmmpff:(.

The new pressure switch is installed. The error is still occurring:(.

It would also have been strange if a pressure switch had a defect straight from the factory (the switch has already been replaced once).

Well, so again nothing (€116.00:(). At the workshop, they bypassed the switch; supposedly, the fan then switched to the second speed. Very rarely, the fan also runs on the second speed setting (but it has always been like that).

So, a new control unit then?

@Andy,

You're talking about a control unit for the air conditioning fan. Where is it located? Or is it located in the Climatronic control unit?

Since I'm not very good at soldering, I'm going to try using a new Climatronic control panel from eBay.

Is there anything I should keep in mind? How can I check if the part listed on eBay is compatible with my car model (or are all parts the same for Golf IV and Passat?), and how can I verify that it's in good condition?

Greetings.
Peter.