Hi guys . Strange problem with my car both radiator fan work on Cold start ! AC off and engine cold . Could it be faulty temperature sensor? Relay? ECU ? . I conected the code reader there's no codes . Any ideas?

Thanks.

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Can you decipher if it’s on low or high fan speed?

 

Unplug the connector from the AC pressure switch (front left corner of the engine compartment) and, if the fans stop running, the pressure switch is faulty.

 

Low speed .

 

I will try that thanks.

 

I did unplug the the AC pressure switch and the fans stopped running so probably the switch is bad . Should I change that switch? I mean there's no overheating or something really bad in the AC system or the cooling system everything works fine .

 

try cleaning the connectors to the switch: but if it is leaking, it is broken.

 

​​​​​​Couldn't find any leaks. New switch cost 120$ .
Im not really sure if I must change it everything works fine but fans works on cold start . Will this faulty switch cause any further damage or problems?

 

With regard to the fans operation, the pressure switch has two steps: pressure up to 22 Bar, Low Speed; pressure above 22 Bar, High Speed comes on. The question is whether the switch, having a fault in its contacts for low fan speed, will operate correctly or not when the high fan speed is required. If the switch does not trigger the high fan speed on time (at 22 Bars), it will cause AC system to get overheated and overpressurised. Otherwise, the AC triggered high speed will only be required in hot weather and when sitting in traffic.

Another negative side is that, if the fans are running all the time, their life span will be reduced. In normal operation, the fans will practically not run at all when moving at speed on an open road/highway (except in extremely hot weather) as the natural air flow will be sufficient to cool both, the AC condenser and the engine radiator.

Other than the above described points, there are no other issues if the fans are running all the time at low speed.

 

​​​​​​Thanks a lot . I tried to change the pressure switch but once I opened it alot of green oily stuff came out so I closed it immediately I think the high pressure hose need to be replaced too

 

There should be a Schrader valve in the extension of the high pressure pipe onto which the pressure valve screws. You may try to replace the valve only (if it can be unscrewed), if the hose still looks good.

 

I bought the high pressure hose from scrapyard it looks in very good condition 35$ it came with the switch too . So the mechanic discharged the AC system and the changed the hose along with the pressure switch then add about 100ml pag oil then R134 Freon to 40psi now everything's works correctly.

I believe the oil in the AC compressor doesn't have the correct amount of oil because I had burst hose time ago and all oil came out ,what makes it worse I discovered the AC compressor had ATF fluid in it didn't know that until the hose Burst

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How would ATF get in ?

That hose failed on one of my 02's -- it gets a lot of heat and pressure .... I think it comes with the sensor or maybe I just replaced mine. It was a long time ago ..

For long term reliability the R/D should have been replaced .

 

I'm third owner of this car so probably there was a problem in the ac system so that mechanic filled it up with ATF and Freon probably he didn't have AC oil such pag100 or other oil.

When I pulled the intake manifold to replace the 2 coolant hose there , I discovered there was no intake manifold gasket!! So someone used filling silicone to work as intake manifold gasket!

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Sadly -- this is common with older luxury cars. Second owners when the car is relatively new are typically not bad. When you go down the line of owners no one wants to get the correct part and the car becomes a hack all over the place .... even something as simple as coolant. Putting ATF in a AC system ... that's a new one. Who knows what that does over time.