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Doug, ASE Certified Technician
Category: Volvo
Satisfied Customers: 8531
Experience:  Volvo Enthusiast and extended work experience from a Volvo specialized shop
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Volvo V40: heater fan..the climate control unit..removing..joints

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Volvo V40 1992 heater fan working erratically. I have replaced the transistor pack on the fan as well as the pollen filter. Still no joy, so removed the climate control unit from the dash and stripped back as far as removing the pcb and checking the fan potentiometer for dry joints. Resoldered the joints on each of the 3 legs from the fan speed control and things are better (better fan control, no hunting and speeding up/slowing down of fan on its own). Symptom is that there are no lights on the CCU for a few minutes after starting the car. After a few minutes, the orange light comes on under the fan control knob and all works well. Up until this point, the unit has no control - no heated seats or rear window. The colder the weather, the longer it is before the fan kicks in and the CCU works. Is it really dry joints on the CCU PCB or is another component failing? How much are these things to replace new (they seem pretty rare 2nd hand).

Unfortunately the boards in the CCUs on these cars are notorious for this type of behavior, and it is typically cold solder joints. While you can often sweat the joints and improve the condition on the fan and temp pots, many of the other joints are too small to effectively access without damaging other components, and replacement is the most optimal solution.

If you are having the entire head go dead in the morning/cold weather, as long as your plugs are solidly connected on the back, this is certainly a dying CCU. The power lead into the unit is direct, and obviously a fuse failure is not going to be an issue here (once they blow, they are gone, they won't come and go).

New replacements are as hard to come by as used ones, and depending on year/model can clear $750US. For this reason used replacement is the best bet. For the US models we only have 5 years worth, so there are even fewer out there; here we have two gambles available to us.... as-is used ones for $5-50 and cross your fingers, or used units from reputable breakers like erievovo that will sell for much more (usually $200-300) but offer lifetime warranty/exchange service.
Doug, ASE Certified Technician
Category: Volvo
Satisfied Customers: 8531
Experience: Volvo Enthusiast and extended work experience from a Volvo specialized shop
Doug and 5 other Volvo Specialists are ready to help you
Customer: replied 4 years ago.

Hi and thanks for the reply. I suspect the cold joint is so marginal that the contraction of the board in cold weather makes all the difference. As soon as power is applied to the board and it begins to warm up, the joint is reconnected. Two of the joints were easy to fix, but as you say, the third is so close to another component that even with a fine-tipped soldering iron it is not possible to fix properly. I did read that sweating the joints often didn't work and that resoldering was the only option. From underneath that is not a problem, but doesn't make the connection. From above it is impossible unless you are a robot! I might have one last go at it whilst keeping an eye on Ebay. I did try some UK breakers and they quoted between £40 and £120, but when I supplied them with the part number they all went quiet, so I suspect they were quoting for older units from the old style V40.


Thanks for your reply and it is good to know that this isn't an isolated case. One good thing is that I can solder a lot better now than I previously could!




Yes it is all about temperature, as the issue is dirt/pockets in the solder joint, and as the metal contracts/expands with temperature changes these pockets shift causing bad connections. This is why sweating and letting the solder reflow corrects these issues. In my experience, with the speed and temp pots it is best to use a solder removal tool to clean the old solder out entirely and replace with new, as even resweating the joints can sometimes come back a year later, indicating the solder is just plain dirty.

Good luck!

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