What A/C Component Activates Engine Cooling Fan

wanderdüne · Post by **wanderdüne** » 15 Jun 2018, 08:30

Hi, I'm having problems with my a/c in my 2003 T6. It is blowing cold at first, then warm. A signal feature of this is that the engine cooling fan engages at highest speed really loud when the compressor is engaged. I have to think that this is related to the problem and hope that if I can find out what controls the fan, that I might be able to diagnose the problem.

I do have a scanner that can read and scan all of the modules, but I do not have Vida Dice yet.

I can say that the cabin temp sensor in the climate panel is off by ~25*F too high of a reading; ex:~71* in the cabin, reading 95* on my scanner.

Anyway, I have no idea what sensor or switch controls the engine cooling fan from the A/C side of things. Would help me a great deal if I knew where to start looking.
Thanks

Post by **oragex** » 15 Jun 2018, 09:01

Hi, when it blows warm, have you looked see if the clutch plate is running?

Not sure about this one but there is a sensor inside the evaporator box, however this little guy rather fails open causing the air to rather get too cold www.youtube.com/watch?v=s1vIWTG9-Zw

I'm guessing it's the engine coolant sensor that will trigger the fan blower speed at max when the engine gets very warm (such as when letting it idle at rest in a hot day). May as well be an issue with the cooling fan controller (a box located right on the fan)

Note that as the cooling fan goes faster, in theory this should help the refrigerant get colder, this is why I'm thinking the clutch is disengaging because of the gap (google up)

You may possibly have two separate issues

wanderdüne · Post by **wanderdüne** » 15 Jun 2018, 09:14

Thanks,
I'm not sure that it's the CTS, the fan goes to high speed just after I start it up in the garage and the CTS is reading normal temps through my scanner. The clutch does engage but only briefly when it gets warm.
I am not getting any DTC's and the ECM is not seeing the engine fan turning on, that is why I think that it is engaging from the A/C system somewhere.
I do plan on testing that sensor on the evaporator later today when I can find the Ohms values for it.
I am reasonably sure that the engine fan is operating normally outside of when the a/c is on.

Post by **ggleavitt** » 15 Jun 2018, 13:06

For what it's worth-

The engine cooling fan (FC) has two functions. One is to cool the engine compartment, the other is to cool the condenser when the air conditioning (A/C) compressor is working.

The engine control module (ECM) transmits a pulse width modulated (PWM) signal to the engine cooling fan (FC) control module. The control module then activates the fan at different speeds. The speed of the engine cooling fan (FC) is determined by the engine control module (ECM), depending on the coolant temperature (based on the signal from the engine coolant temperature (ECT) sensor) and the vehicle speed. The temperature conditions for engagement of the different engine cooling fan (FC) stages may vary slightly, depending on the engine variant and the equipment level.

The temperature conditions apply when:
-The A/C is off
-No faults are detected by the Engine Control Module (ECM).
Note! The engine cooling fan may have a post-run of up to approx. 6 minutes after the engine has been turned off. The time for the fan's post-run depends on engine temperature, temperature in the engine compartment and pressure level in the AC-system.

The engine cooling fan (FC) and its control module are behind the radiator.

The engine control module (ECM) can diagnose the engine cooling fan. The fan can be activated using VIDA.

wanderdüne · Post by **wanderdüne** » 15 Jun 2018, 13:21

OK, took it out for an errand, 94*F outside, then scanned some things when I got back home.

-A/C wasn't working. Compressor would just cut in and out- was reading 258-300psi, then blip up to 400psi when the compressor was on briefly.
-Evap temp. was 104*F
-Coolant temperature was reading 285*F, thinking that is not accurate? Maybe a problem there after all.
-Cabin air temp reading 113*F, Actual was 86* by thermometer resting at the same location.

Thanks ggleavitt,
So looking like the A/C system has no engine cooling fan control.
Would the ECT throw a code if it were bad?

Post by **jimmy57** » 15 Jun 2018, 13:36

There is a high side pressure sensor on the right side by condenser. Access is by removing front bumper. The ECM will get pressure value from that sensor and run the fan at variable speed to keep pressure in desired range. Also the pressure reading will cut off compressor when it exceeds approximately 400 psi. It shouldn't go much above 300 psi for a very hot car on a 100+F day. If fan is working and there is no air path blockage then the high pressure is due to blocked condenser refrigerant path or expansion valve obstruction or sticking. Water spray on condenser will often bring high side pressure down to resonable level even with intrnal blockage as the water will condense refrigerant at several times that of air cooling. Water would not bring down expansion valve caused problems so readily.

Post by **oragex** » 15 Jun 2018, 13:55

wanderdüne wrote: ↑15 Jun 2018, 13:21
-Coolant temperature was reading 285*F, thinking that is not accurate? Maybe a problem there after all.

Seems really high. Normally it will not go past 200F or so with the thermostat fully opened and the fan spinning. Sounds like the fan is spinning high because it thinks the coolant got too hot, maybe faulty ECT ?

Try reading the high pressure with the engine off, see if it drops relatively fast and steady to a lower value. If not the expansion valve can be stuck closed.

Post by **ggleavitt** » 15 Jun 2018, 15:26

Taking a guess and this is a 2003 so has the older (all number) codes, but if there was a code being thrown it could be ECM-6000 (AC), ECM-6100 (Engine cooling fan control module), or ECM-6110 (Engine cooling fan relay), with each code to be followed by a descriptor (Signal missing, too high or too low). These are the Volvo codes, somebody can do the OBD conversion (I have a list but think it's the newer post 2004 number/letter codes). VIDA with a DICE can test the fan at variable speeds I think as well as get some real-time metrics (fan speed, temp, etc.). Good luck !

Post by **ggleavitt** » 15 Jun 2018, 17:54

I read the first post a little closer. Fan turns on to full or near full speed when AC compressor is on. Per VIDA, that's maybe "normal".

Was thinking about the "cabin temp" sensor comment though. This is the temp reading from the little text box under under the RPM gauge? If yes, that's outside temp, comes from the passenger mirror side thermistor I believe. New mirror in this car or has it always been like this? I got one of these from Erie a few years ago, mirror worked great temp was waayy off, they swapped me for a good one, great folks.

At any rate, if the car's assumed outside temp is reading far more than the real outside temp, turning on the AC is maybe going to cause the CCM to expect the car to cool down far more than it would otherwise. Could absolutely be something wrong which has the AC on all the time triggering the engine fan in turn to run full blast all the time. In my mind that's another possibility to consider.

Bet if you can get a Volvo tool on this car, you'll have a better idea where the issue is coming from.

Good luck !

**edit- Fan may be on full, may not be on full.

wanderdüne · Post by **wanderdüne** » 15 Jun 2018, 20:09

Thanks all,
The cabin temp I referred to is the one from the CCM itself behind the tiny grill on the face of the unit. Not really sure how that effects things. I rented a manifold gauges today and it is reading a really high pressure on the high side ~350-400psi and pretty normal pressure on the low side ~45psi @85*F in my garage. Based on the sheet that came with the gauges unit, it looks like it may be the expansion valve is clogged. Going to take it in in the morning to the Tunex by me to get it evacuated and see how much they want to replace that and the receiver drier.

Looks like the least expensive option for me on the temp reading front would be to replace the CCM temp sensor (the xemodex CCM unit is over $500 USD, I think), but I think that it needs to be programmed to the car afterwards. Anyone know if Vida Dice can do that?