Radiator fan runs continuously

[millsa99]

Hi,

I have a problem with the radiator fan running continuously.

History: Problem occurred a few months back and the mechanic replaced the high pressure A/C sensor. This stopped the radiator fan running all the time and also fixed the lack of cold air from the air-conditioning.

However, the problem has come back with the radiator fan.

Anyone had this problem and do you know the fix?

Thanks
Andrew

[dogface]

I have opposite problem--my fan never turns on, even when engine is hot as hell. If you can find the engine temp sensor (I dont know where it is), try unplugging it, then try unplugging the fan relay. the relay might be stuck closed.

[millsa99]

A lot of people of this forum and Matthews have had the same problem. They describe the problem but no answers come up and then they do not return to point out the answer. Please, does anyone know?

[Willy]

I believe the most common cause of a radiator fan either not running or running all the time is a failing
driver module. This is a (darlington) transistor circuit and can fail open or short.
However, since Andrew's problem was (temporary) fixed by replacing another part, this seems to indicate
the problem may very well be something different.
The module (item 4/71 in the pdf) is part of the fan assembly itself and can't be replaced seperately :-(
Willy

[millsa99]

Thanks for the replies. According to Volvo mechanic, when the pressure in the aircon gas goes below a certain PSI the radiator fan switches on by direction of the high pressure sensor. As to why an idiot would design a system in this way is beyond me.

Found a leak in the condensor. Evidently fixed although something tells me I'll be back.

For the record, mine is a 2005 XC70 with 75.000kms on the clock. I have never had more problems with a car. Volvo truly are crap.

[Astro14]

Sorry you're having trouble with the car, the Volvos that I have owned have been more reliable and cheaper to own than my friend's BMWs (Bring My Wallet) or other european cars.

But to your question on why the AC can switch on the fan - it's pretty simple. Look where the condenser is located: just in front of the radiator. The AC efficiency depends on the condenser being able to reject heat and condense the freon, so that it can be evaporated inside the car to remove the heat from the air blowing into the passenger compartment. If there is not enough air moving across the condenser, then the cycle doesn't work because the freon isn't cooled enough.

In that case, the radiator fan kicks on to draw air across the condenser. One fan, two uses - efficient engineering....

[millsa99]

Thanks Astro. But if there is no gas in the AC and they took the effort to place a high pressure sensor on the system, why not just shut down the AC through the computer and send an error message. Making the radiator fan go to max is just stupid and inefficient.

[Willy]

Thanks Astro. But if there is no gas in the AC and they took the effort to place a high pressure sensor on the system, why not just shut down the AC through the computer and send an error message. Making the radiator fan go to max is just stupid and inefficient.

Perhaps, but this is still in the assumption that it is indeed the A/C system that keeps
the fan running and if I am not mistaken, this is not (as yet) proven.....
Therefore, it may useful to keep an open mind as to the cause of the problem.
Willy

[Blue_V70XC]

I am late to the party, but I find that, on occasion, my radiator fan and/or my blower fan (for cabin circulation) will operate of their own occord. My independent Volvo mechanic tells me that there are temperature sensors for both situations that will cause the fans to operate to help keep temperatures under control. And a friend who is a technical writer for BMW tells me the same thing about that brand.

And in both cases, this information is not contained in the operators manuals, so owners think something is wrong, thereby spending precious funds at the dealership for no good reason.

[NJ03XC]

I had this issue about a year ago. Fan ran nonstop, even after parked in the garage for 2 hours. I disconnected battery to keep it from running down and went to a good local indy. They told me, as Willy said above, that the controller couldn't be replaced independently of the fan. They replaced complete fan assembly and all has been fine since.... at least with that portion of the car. Kind of a drag that the controller can't be replaced w/o trashing what is otherwise probably a fine fan assembly.