user 20389

I don't know if I have a problem or not. Last week the car overheated (way hot and heater did not blow hot). figured that it was thermostat stuck. Filled with coolant and now it runs fine. temp is on the 0 of 180. I burped it good. when it overheated I recall both radiator fans running. Today I wanted to check it again just in case and all was well (temp the same and fluid stable, heater blows heat) but it seems that only one fan is blowing. Is this normal or does both fans react the same, both running when running at all? Thank you in advance for your suggestions.

Macster

Both fans should run at the same time. The fans are turned on when coolant reaches 212F. They are switched off when the coolant temperature drops to 205F. If the temperature climbs to 216F the fans are switched to high speed operation.

If the A/C is on the fans run all the time, at least at low speed, but high A/C demand or elevated coolant temperature can have them switched to high speed.

Over the years had a couple of radiator fan issues... First one was with my Turbo. Passenger radiator fan motor was running but no air flow. Turns out the motor shaft had snapped. Tech said he had *never* seen this failure before.

In the Boxster the passenger side radiator stopped working at low speed. This is a "common" problem and is often a problem with the ballast resister in the fan harness. Techs have told me that often when a car is worked on the radiator fan wiring harness is not routed as per factory and as a result is located out of the air flow which causes the resister to run hotter which can result in shortening its life. Also, if the harness is not routed correctly water splash can hit the resister and if it is hot can damage it.

Another time the driver side fan of the Turbo was running and moving some air but not nearly as much as the other side which was blowing a gale. Tech checked and found no fan stage errors but found the current draw of the driver side fan way higher than the current draw of the passenger side fan. I had him replace the driver side fan motor and all was well again.

If both fans are not running or of both fans do not appear to blow the same amount of air there's a problem. I did not do any real in depth diagnosis. My attempt to get to the bottom of what was going on was to just confirm one fan was not blowing any air or not blowing the same amount of air as the other side. In the case of my Boxster, the tech confirmed the ballast resister was bad. In the case of the Turbo he found the fan laying down behind the radiator. And in the 2nd Turbo radiator fan problem he connected the Porsche diagnostic computer to the car and checked for fan stage errors and then checked current draw.

user 20389

thanks for your help. Will make sure that both are running and output same before I do anything else. thanks again