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S40 fan speed erratic

Help, Advice, Owners' Discussion and DIY Tutorials on S40 and V40. In this forum you'll find S40/V40-specific owners asking and answering questions on maintenance, ownership, repairs, tutorials and almost every do-it-yourself thing you can do to save money owning these Volvos.

1996 - 2004 S40
1996 - 2004 V40

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tr_car_nut
Posts: 17
Joined: Wed Feb 09, 2011 2:19 pm
Year and Model: 2000
Location: North Carolina

S40 fan speed erratic

Post by tr_car_nut »

When I bought my S40 several years ago the fan for the climate control was not working so I replaced the fan resistor module (under the glove box) with one from a salvage car and everything began working again. Fast forward to today and now the fan speed and possibly the temperature side of the climate control appear to be all over the place no matter what I have the controls set too. Is this a problem with the head unit in the dash or could this be a bad transistor on the fan resistor? I'm tempted to buy a used climate control from eBay but I think I might just end up with the same problem. Not to mention the knobs are so sticky now.
2000 XC70 (113,450 miles) CEL P0422 after new fuel pump
2003 S40 (186,000 miles) re-assembling.
1999 S70 (170,500 miles) everyday driver now
kstinmb
Posts: 9
Joined: Mon Feb 25, 2013 1:36 pm
Year and Model: 2001 S40
Location: Myrtle Beach SC

Re: S40 fan speed erratic

Post by kstinmb »

We have a 2001 S40 and for many years (!!) now, the blower has been running erratically, fast/slow/stop, no matter the settings, heat or A/C, speed number or AUTO.

I replaced the entire Final Stage Resistor and it had no effect ($65).

Image

A couple of weeks ago I bought a replacement control panel from eBay ($100) (matching part number).

Image

But this also has had no effect. The blower still runs fast-slow-fast-stop-slow-fast, etc. The one nice aspect is that we now have buttons which aren't sticky!

Is there something else that controls the speed of the fan?

Has anyone replaced the blower motor itself?

Thanks,
-stephen
Myrtle Beach SC
2001 S40
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alschnertz
Posts: 649
Joined: Fri Apr 29, 2011 9:25 am
Year and Model: 1995 854T
Location: Connecticut
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Re: S40 fan speed erratic

Post by alschnertz »

Just noticed the same thing on my daughter's '01. As soon as I turned on the fan, it would vary in speed without any input from me.
I'm suspecting something like a broken solder joint on the ECC board, but would also like some other suggestions.
Hopefully someone will chime in.
And yes, those gooey knobs are awful.
'60 PV544, '68 220, '70 145S, '86 745T, '95 854T, '01 S40
'84 Prelude
'06 MPV
'13 Ford Focus SE
Livens
Posts: 54
Joined: Fri Dec 20, 2013 7:09 pm
Year and Model: 2003 S40
Location: Lou, KY
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Re: S40 fan speed erratic

Post by Livens »

The issue is corrosion inside of the potentiometers that control the fan speed, air level and temp. I took my module apart a year ago and sprayed a product called Deoxit 5 on the pots and worked the back and forth as per the instructions on the can. This completely fixed the problem, fan speed was steady as a rock... until about a month ago :(. So it lasted a year. I'm going to clean them again, this time I'm spraying the heck out of them! The can says to just use a tiny bit, just a quick blip... I'm going for broke this time :)

In another forum someone posted that you can buy replacement pots and solder them in for a more permenant fix. I've replaced capacitors on PC motherboards with good success... but honestly I'm tired of dealing with the crazy fan speeds, and some fan speed is better than no fan speed in the summer. So if the cleaning doesn't fix it this time I will just learn to live with it.
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pierremcalpine
Posts: 73
Joined: Tue Jun 18, 2013 7:38 pm
Year and Model: V40 2003, V70 2010
Location: Toronto, Canada
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Re: S40 fan speed erratic

Post by pierremcalpine »

I had the same issue and did end up replacing the POTS. Easy job (this coming from someone who had to learn to solder to get this job done). The trick is to find an equivalent POT. I ended up getting one from a fellow in the UK who had purchased a few extra ones when he did his. It has now been two years and all is well with the previously possessed fan.
kstinmb
Posts: 9
Joined: Mon Feb 25, 2013 1:36 pm
Year and Model: 2001 S40
Location: Myrtle Beach SC

Re: S40 fan speed erratic

Post by kstinmb »

I tried using spray contact cleaner with a tiny straw nozzle, but I'm not sure any actually got inside the potentiometers. At any rate it made no difference. Is it just coincidence that both of my controllers behave the same way?

If I can locate the pots (I believe I saw a source on another Web site) I'll swap out a set and see what happens.

Is there any other component involved in this problem besides the control panel, final stage resistor and blower motor?

Regards,
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pierremcalpine
Posts: 73
Joined: Tue Jun 18, 2013 7:38 pm
Year and Model: V40 2003, V70 2010
Location: Toronto, Canada
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Re: S40 fan speed erratic

Post by pierremcalpine »

I don't believe so. If/when you replace the POTS (make sure you do both temp and speed btw) you may need to manually calibrate the speed dial if the fan speeds do not behave As expected. You will immediately know this is the case if fan does not turn off "0" or turn to auto when in auto. All you have to do to correct this is to carefully soften up the plastic spindle behind the dial and twist it slightly and let cool off and test until you get the fan calibrated. Told that this is because the POTS get calibrated to the panel in the factory.
steve090
Posts: 13
Joined: Thu Aug 21, 2014 9:48 am
Year and Model: 2003 S40
Location: Texas

Re: S40 fan speed erratic

Post by steve090 »

On my 03 S40, I had a bad actuator which I replaced but mine still runs eratic minus the annoying click from the old actuator.

I find that it runs well in 2-3 above 3 it becomes more eratic
Nandha
Posts: 1
Joined: Fri Jun 13, 2014 5:45 am
Year and Model: S40 2001
Location: South Africa

Re: S40 fan speed erratic

Post by Nandha »

tr_car_nut wrote:When I bought my S40 several years ago the fan for the climate control was not working so I replaced the fan resistor module (under the glove box) with one from a salvage car and everything began working again. Fast forward to today and now the fan speed and possibly the temperature side of the climate control appear to be all over the place no matter what I have the controls set too. Is this a problem with the head unit in the dash or could this be a bad transistor on the fan resistor? I'm tempted to buy a used climate control from eBay but I think I might just end up with the same problem. Not to mention the knobs are so sticky now.

I had the same problem a few years ago. Replaced brushes on the blower motor. Works fine until now
lama15
Posts: 3
Joined: Sat Jun 27, 2015 11:33 pm
Year and Model: 2001 S40
Location: Central Valley CA

Re: S40 fan speed erratic

Post by lama15 »

I just went through a similar situation in my 01 S40. It started with my fan being erratic while driving. Then it would only run half the time with better results when starting the car with the setting to 0. But then it completely wouldn't work. I noticed it would be cold when driving at freeway speed, but no fan. I ended up swapping out the transistor with a new replacement and had no change. I took the blower motor fan out and noticed when i held upside down, it spun perfectly (likely due to the lower resistance), but when i held it rightside up again it would stop spinning. I ordered a new fan and installed today; is running perfectly with more fan power than i can remember having in the past few years.
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