Problems with your AC compressor?

This weeks technical post is to inform you why AC compressors fail after replacing OE condensers with a non OE condenser, and how this affects your AC system.

According to OE manufacturers, Denso, there has been an increase in warranty claims for compressor failure following the replacement of an OE condenser with a non OE condenser. But what causes this failure?

Denso have found that the most common reason for failure is flux. This is a chemical commonly used during the production process of the non OE condenser, and finds its way into the condenser tubes. This then goes on to start a chemical reaction with the UV-Dye and Oil. Not a good combo!


Flux is mostly used for the aluminium brazing process during the manufacturing of a condenser. Because of the poor production quality of some non OE condensers, the flux can enter the condenser tubes during this brazing process. When a workshop installs these non OE condensers, the flux inside the condenser tubes comes into contact with the UV-dye.
During AC system operation, the flux and UV-Dye starts mixing and causes a chemical reaction with the oil. This turns the oil into a jelly like, sticky substance. Immediately after the repair, the AC system operates without any issue. The problem starts after the engine has been switched off and the AC system cools down. During the cool down period, the sticky oil causes the pistons to bond to the cylinders. The compressor will still rotate, but remains in the minimum displacement position, thus not giving the required cooling performance.
Well, it actually means that you will have a higher rotational torque. The rotational torque of a contaminated compressor is higher – it also has a “sticky” feeling when rotating the compressor shaft for the first time.
  • The brazing flux can be found in several forms – a powder, a liquid or a gel. The problem arises during the aluminium brazing process. On non OE condensers, the flux enters the condenser tubes.
  • This “contaminated” non OE condenser is then installed in your vehicle. You could say that it is all downhill from there…

As you can see, once you’ve got the contaminated non OE part fitted to your vehicle, it’s only a matter of time before the damage is done. But fear not! Opies stock a huge range of OE products from the best of the best – Denso. Use our handy look up guide to find all air conditioning and heating parts HERE, you can find the full range of Denso quality condensers HERE.

At Opies, we like to stress the importance of using OE parts, as the quality speaks for itself, but we also believe that using non OE products is a false economy – why risk fitting a poorly engineered part that has a high chance of failing, only to save a bit of money, when the OE product is a guaranteed fit and will be up to spec. Don’t forget you can also get a 10% discount with the code OPIEBLOG.

If you need any further advice on the correct parts for your vehicle then we are only a phone call away on 01209 202 944 or drop us an email to We’re in the office Monday to Friday, 8:30 – 5:30.

Until next time!




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