2001 S40 A/C only blows on high or off

grileaux · Post by **grileaux** » 21 Sep 2015, 20:01

I recently bought my 2001 S40 with 94k miles. Since I bought it, the A/C only blows on High speed and Coldest setting (which hasn't been necessarily a problem for this summer in South Louisiana). I thought I needed a blower motor resistor so I bought one and replaced the 'bad' one. I replaced the motor blower resistor with no result (still blowing cold on high). However, I did notice a copper wire placed in the female plug that connects to the resistor (pictured below). So, i took that copper wire out the female plug and the A/C instantly stopped blowing (shut off) entirely. I tried plugging the female plug into the new and old resistors with no promising results. With the copper wire in the female plug, the a/c blows on high/cold, whether it's not plugged in, plugged in to the new resistor, or plugged into the old resistor.
And with the copper wire removed from the plug the A/C shuts completely off whether plugged into the old resistor or new. I'm looking for help both diagnosing and solving this problem. Thanks in advance for any and all help y'all.

Post by **regent** » 22 Sep 2015, 09:32

Check out the diagram:
It looks like somebody ‘corrected’ a wiring fault (open) between pin 4 on the ‘Blower Resistor’ 4/14 and Junction Point 43/400 by placing a jumper on the connector, and that is why you only have MAX blower speed, even with a known good ‘resistor’ 4/14 (which is in fact an pulse-width modulated electronic regulator).
Can you remove the jumper from the connector and check if you have good continuity between pin 4 and 43/400; if good and still no variable blower speed, then you need to check if the PWM control signal from the CCM is present at pin 3 (input) on the Speed CTRL (‘resistor’) 4/14. You will need a scope to check that input.
Hope this helps,
Please post back what you found.
Thanks

grileaux · Post by **grileaux** » 22 Sep 2015, 15:29

Thanks for the information and diagram. Here's where I'm at, with my limited understanding and ability to apply the information you've provided.

I removed the jumper from the connector and connected it to my speed CTRL, which I (mis ?)understand to be pin 4. The connection is fine but yields no effect.

Then I used the scope to test the voltage coming from the connector. I was testing alternating current voltage (acv) , do I need to test acma, dcv or dcma? With the acv test, I was receiving no voltage with the jumper removed, and the negative from the scope grounded.

I'm not sure how well I followed your direction and I'm getting a grip of this diagram, which I'm ashamed to say May be the first diagram of an electrical circuit I've studied since high school.

Thanks for your time and help, I look forward to hearing your response. I'll attach a photo of how I used the scope.

grileaux · Post by **grileaux** » 22 Sep 2015, 15:33

* one more note*
With the connector removed from the speed CTRL and the jump removed from the connector, I believe the air conditioner is still on, only not blowing. I say that because under my glove box, where we're working, there is cold condensation and the a/c seems to be making sound like it's on, though the fan isn't blowing.

Post by **regent** » 22 Sep 2015, 18:37

OK, let us do a simple test:
Jumper is removed from female connector, connector is plugged into the 'resistor' (where it belongs), ignition is ON (the engine does not need to be running).

1. With scope in DC Volts mode, on pin 2 you should read 0.00 volts (relative to chassis/ground) you should read 0 on Pin 2 as it is supposed to be grounded at 31/1 via 43/401.
2. On Pin 3, with scope in AC Volts you should read CTRL pulses from CCM to 'resistor', (the PWM duty cycle will change as you move the knob for the speed control from MIN to MAX)
3. On Pin 4, you should have a pattern similar to what you saw on Pin 3 (only it would change in the opposite way as you move the knob). The Speed CTRL 'Resistor' is a Pulse-With modulated switch to ground. Only when the knob is in MAX, you should read 0.00 (or very close to zero) on Pin 4.

The above readings are on a good working system.

Let me know what readings you are getting (I am suspecting that the pulses from the CCM that should be coming in on Pin 3 are not there, regardless of the knob's position. Hope we get this sorted soon.

grileaux · Post by **grileaux** » 22 Sep 2015, 19:57

* Should my glove box be taken out for proper access to these components?
Your help has given me great hope and excitement about this project and broadening my practical knowledge.
We spent about 10 hours this weekend fixing stripped wiper arms and getting the wiper timing back in sync, great learning exp.
That being said, I need a little patience, because I'm still figuring out what is what with the diagram. Do you know if it has a key, of if there is a general circuitry diagram key that may be useful for me?
Thanks again brother.

Post by **regent** » 23 Sep 2015, 07:22

I am attaching your complete diagram; with keys and guides at the beginning.

For now, let us not start taking the whole car apart (at least yet)

This could be just a broken wire, recessed pin, bad potentiometer (the speed control knob) or a bad CCM (worst case scenario). Let us see the readings at the connector first and we'll go from there.

On another note, are the rest of your climate controls working (air distribution, air temp controls); you should hear the servos responding as you move the controls, and this is best done with the ignition key in pos I or II (engine is OFF)

Post by **regent** » 23 Sep 2015, 07:42

If you do not have VIDA, this might help you with the components' arrangement:
http://volvopartslisle.com/assembly/628 ... r-Controls

grileaux · Post by **grileaux** » 23 Sep 2015, 16:31

Thanks for everything, I'm currently ingesting some info.
My climate controls are not working.

grileaux · Post by **grileaux** » 23 Sep 2015, 17:38

TEST RESULTS*
1. With scope in DC Volts mode, on pin 2 you should read 0.00 volts (relative to chassis/ground) you should read 0 on Pin 2 as it is supposed to be grounded at 31/1 via 43/401.

Scope modes; DCMA:0.00 DC10A= .000 DCV= Variable; I could not get a constant reading on this setting

2. On Pin 3, with scope in AC Volts you should read CTRL pulses from CCM to 'resistor', (the PWM duty cycle will change as you move the knob for the speed control from MIN to MAX)

Reading was about ACV=.007 with no change when I adjusted the knob.

3. On Pin 4, you should have a pattern similar to what you saw on Pin 3 (only it would change in the opposite way as you move the knob). The Speed CTRL 'Resistor' is a Pulse-With modulated switch to ground. Only when the knob is in MAX, you should read 0.00 (or very close to zero) on Pin 4.

Reading was about ACV=.000, also with no change when I adjusted the knob.

It appears that your hypothesis that "the pulses from the CCM that should be coming in on Pin 3 are not there, regardless of the knob's position", is correct.