05 S60 2.5T AWD: Cooling fan runs when engine started

[MarcM]

This started happening a month or so ago. I unplugged the fan and plugged it back in (thinking terminal oxidation as a possibility for some sort of feedback circuit). No dice. I saw the thread with the guy with the 0030 code, so I cleared the ECM (battery cable method). It's taken until now for it to start doing it again and the ECM now has a DTC set since the fan started running the other day.
Basically, I can put the key to run and the fuel pump pressurizes the system. That's it. Within seconds of the car starting the fan winds up running. If memory serves, word was that the IAT goes to hell. Tomorrow I'm going to throw the DMM on the IAT sensor to see what it ohms out to. I have this info as I got Vida 2014D to work with Win10 and can at least use the app, but can't read the codes (but no Dice (pun)).

[oragex]

I don't think the IAT fails too often, still a good idea to give it's small wire a cleaning if it has never been done.

I don't think the IAT would cause the fan to came on, however. Perhaps, the coolant temp sensor is related (located on the thermostat housing), this guy does fail sometimes, it can also be an air bubble trapped inside if the thermostat bleeder is not well positioned. The fan controller box located on the fan assy can also go kaput after a number of years as it's has two capacitors inside that start leaking.

[MarcM]

I don't know why I said the IAT sensor is in the MAF. It's part of the boost pressure sensor on intercooler. Shots fired because the lady wants to go somewhere... but here is the resistance spec from Vida across pins #1 & #2:
5886 Ω @ 0°C (32°F)
3791 Ω @ 10°C (50°F)
2510 Ω @ 20°C (68°F)
1715 Ω @ 30°C (86°F)

Maybe I can do this in the parking lot while she's bouncing around inside a store or something. Posting here so I can find it on my phone for future reference.

As far as the ECT sensor. Put in brand new. It came installed with the Beck/Arnley thermostat housing. The first thing I did was loosen the halves and put the bleeder straight up. Learned that from one of Robert's YouTube videos before I found the forums (which, BTW, I've basically abandoned the other one as MVS people seem to be more patient). I do have a spare ECT sensor I bought before the thermostat housing replacement.

[DGM]

Low A/C charge could cause this condition. See the following thread;

https://www.matthewsvolvosite.com/forums ... =9&t=50104

[MarcM]

Seeing how I replaced the condenser but have yet to have the system evacuated/refilled.... I'm betting you're right. I have relatives in the HVAC field who offered to do this, but is 1/2 to 3/4 hr away (depending on departure point) and is hard to catch... and in the totally wrong direction I generally travel. Since I'm willing to meet up with Abscate 1-1/2 hrs away, I guess 1/2 hr (from work) to do the HVAC is nothing. Hard to believe 1/2-3/4hr drive whining is coming from a guy who used to drive very long distances on a whim.

[abscate]

MIT tomorrow.

If you don't mention that you need to borrow the vacuum pump and AC manifold set how am I supposed to know to bring that too, on top of the SRS reset scanner?

[MarcM]

My cousin has all the HVAC stuff. As time runs on with my new management job, I'm out straight... just remembered you texted me and didn't respond. Basically I have to drive to Manch-vegas from Concord to get that done. His schedule (business primary) makes it hard to catch up with him at his house. Had plans to go there tonight, but I have no-go smoothies on the car and not up for another tow-out-of-the-ditch incident. So hitting his place first then down to Cambridge probably won't work tomorrow. Doesn't make sense to read the codes without having the AC system evac/filled. I noticed I've lost about .5 mpg with the fan running (was 23.5 avg, up from 21.1). Maybe yet *another* time. I appreciate your wanting to help. Hoping someday the schedules meet.

[abscate]

Once summer hits my Volvos spend weeks in southern MA watching me sail the Cape.....