I have a 2002 S40 and when I have the climate control set to auto (for both fan speed and vent selection) and the temperature set to 76 degrees the fan will come on full blast then almost turn off then turn on full blast then almost turn off and this cycle repeats until I switch to a different temperature. Any ideas on what may be causing this? I am totally stumped.

 

There may be a software issue.Or the climate control module may be going bad.

 

Volvo S40 2001 Climate Control Blower Speed Failure

My Volvo’s Blower Speed suddenly only operated FULL speed as soon as the ignition was switched on.

I found and repaired the following fault which is NOT in the Haynes Service manual, after the agents advised me that I will have to spend a fortune, to replace VARIOUS climate control components ??? They did not tell me what had to be repaired. (I believe they did not know neither.

This Electronic Blower Speed Power Module, is only on the units with Automatic Climate Control (As shown in 1 & 2) and is an electronic control, where in the older units are resistor controlled.

This Failed Electronic Blower Power Module (4) was removed from under the passenger foot well after a long search, next to the blower fan (3), tested and repaired by me.

The module is attached inside the blower housing and accessed after removing the two mounting screws, but the top screw is very inaccessible.
The power transistor, MJ802 was faulty (short circuit) which I removed and a replacement was soldered in place.
Although I did not try it, If you cannot get a MJ802 I am sure a 2N3773 will also work and should last. Ask your local electronics component / radio shack supplier for the MJ802 power transistor.
The MJ802 is a 200 W unit whereas the 2N3773 is only 150W, but is very similar for most other specifications.

Hoping this will help others with the same fault!

I have a more complete Word Document with photo's available for those interested

 

ronbeuke,

I have exactly the same problem as of this morning in my '02 S40. So, it's probably the Electronic Blower Power Module?

I really want to resist taking it to the dealer... or is it wise to take it in for a diagnosis and then fix it myself?