NZ AUTO-AC FIELD SURVEY

SUMMER 2014-2015: PART 6

THE survey of air conditioning faults in 667 motor vehicles, including cars, trucks, tractors and heavy equipment done from 1 December 2014 to 31 March 2015 includes repairs and evaluations by CoolCar Air-Conditioning Centre, Hamilton (more background can be found in September 2015, November 2015, May 2016, August 2016 and December 2016 editions of SightGlass News).

This final instalment of the survey report deals with some of the other, non-refrigerant related findings (sometimes found in conjunction with low refrigerant issues).

In earlier editions, leaking thermal expansion valve o-rings were described as a source of refrigerant leaks in 22 vehicles. In addition, there were 34 examples of faulty TX valve function. Compressor failure due to TX valve liquid slug or a shutdown TX valve was documented earlier but some of these 34 vehicles just presented with a shutdown TX valve.

Not only did pressure switches present as a leak site in seven vehicles but two of those seven were also faulty electrically. An additional seven presented electrical faults at the pressure switch due to component failure or loose connections.

An outside ambient temperature sensor fault presented in a 2004 VW Touareg with multiple faults. The sensor recorded 3.5°C on a 14°C day.

The vehicle had the worn direct drive hub mentioned in an earlier article, a faulty blower motor and compressor control valve.

Replacing the ambient temperature sensor corrected the temperature input but the evaporator was freezing from the faulty blower motor and we believe the control valve faulted because of the changed refrigerant dynamic in the evaporator this brought about.

The customer initially refused to replace the blower motor because it was only faulty ‘sometimes’. 

Another, a 2002 Toyota Corolla had poorly completed accident repairs, including the outside ambient temperature sensor not being properly connected and dangling down at the front of the car. 

A 2009 Ford Falcon experienced a fault with the in car temperature sensor located in the mirror.

A 2003 Porsche Cayenne had a faulty evaporator temperature sensor and the compressor was locked out by the ECU. The compressor could be unlocked and then run with the CTL1 tool. The system also had low refrigerant but no leaks were found with rechecks performed at one month using UV dye in the system. 

A 2007 Kia Picanto experienced an intermittent evaporator temperature sensor fault. 

Five vehicles had faulty air-conditioning thermostats; two Mack Visions, an Antonio Carraro tractor, an Isuzu FRR500F and a Freightliner Argosy. The Macks and Freightliner had the thermostats replaced when they failed to cycle properly after refrigerant leaks were solved and other repairs carried out.

There were 17 instances of controller faults, four of which were due to the controller being unplugged, while another had been tampered with and broken.

In one case the blower motor was noted to be faulty upon re-initiating controller function and another had a leaking discharge hose.

There were several instances of faulty cold solder joints that were able to be repaired satisfactorily in our workshop and others required repairs outsourced from electronics experts or complete replacement. 

On VW Golf and Audi A3 models (as well as Audi A4, but none were encountered in this cohort) deterioration of the blend door flap foam that allows hot air to bleed from the heater and reduce cabin cooling are sometimes accompanied by another air conditioning fault.

Another 15 instances of faulty blend door actuators or flaps were noted along with fresh/recirc flap faults affecting various makes and models.

Cabin filters are often dirty and blocked and may lead to blower motor and fan speed resistor failure – and in a few cases we believe, compressor failure as performance in the evaporator is altered by reduced air flow. Nissan and BMW models are particularly vulnerable to this.

Blocked evaporators continue to provide poor airflow in agricultural and passenger vehicles. A number of cars fitted with cabin filters from the factory had the filter removed altogether and debris had reached the evaporator, which can also block the evaporator drain and cause water to accumulate inside the vehicle.

Loss of AC drive belt on Holden VE and WM V8s

There were five examples of V8 VE Holden Commodores with the AC not working due to loss of the AC drive belt. We concluded the cause was excessively high revs.

A subsequently discovered Holden bulletin describes a service fix for the VE and WM V8 when this fault occurs. They report that investigations concluded the AC belt jumps off the crankshaft pulley due to crankshaft resonance above 3000rpm.

Holden has released a longer drive belt and revised AC bracket incorporating an idler pulley to prevent excessive belt oscillation. According to the bulletin, the existing tensioner is re-used and installed onto the revised bracket but in our experience the replacement bracket may incorporate a new spring tensioner. In addition, the harmonic balancer should be inspected for run-out and replaced if required. Order 92244378 AC bracket assembly, 92244381 AC drive belt (and, if required, 12635649 harmonic balancer and 12557840 bolt).

This recommended repair was not automatically shared with us when ordering parts from Holden, but all VE and WM V8s from part-way through 2009 had this modification from factory. 

Summary

This account of our findings over six parts is not an exhaustive record of what we found but covers the main areas. 

We are reminded every day, as Deyan Barrie writes in TaT Magazine December 2015 that, “Air conditioning [is] as complex as ever – but still a mystery to most”, as many vehicles we see have been somewhere else first, complicating the diagnosis process because their presentation is muddled by re-gassing and botched repair attempts.

Many cars present with multiple issues, both refrigerant and non-refrigerant related and it is amazing to us that companies still attempt to repair cars with a re-gas as the first point of call, even when low refrigerant is not even the presentation in a significant number!

VASA members owe it to themselves to be the creme-de-la-creme and not worry about what the opposition is up to.

Someone has to offer the professional, substantive repair option. Always seek to identify the leak when low refrigerant presents itself without an explanation after accident or major engine repairs. 

Prior to engine repairs refrigerant recovery should have been carried out on both sides of the Tasman in accordance with our environmental protection laws and should be encouraged. To help people make the right decision, we offer free de-gassing at our workshop and a small charge if we travel out to do it.

Invest in good quality gear and trust your leak detection equipment. Consider adding Lok Trace leak detection to your arsenal, which has been used very successfully this past summer. The product manual (tinyurl.com/goyyozr) suggests leak sensitivity at less than 5g/year. Formier gas is available from your gas supplier.