Dan Short wrote:

> I'm not sure if anybody else has this problem, but when I have my A/C

> or heater fan switch down to "0", cool or hot air still

> blows through the vents, depending on what the temp. is set at. Is

> this normal? It's very annoying trying to find the right temperature

> so that i won't roast or freeze when i have the A/C off. Thanks.

Hi Dan

Auto manufactures guarantee fresh air to the occupants with continuous fan operation. The standard set by ASRAE is 15 cubic feet of air per minute per person, this will maintain carbon dioxide levels at around 1000 parts per million ( normal out side air is around 400 ppm ). The human brain seems to function more incoherently when it is not subjected to high CO levels so some incoming fresh air is good. This is fine when your car is traveling very slowly or stuck in traffic but once up to speed the vent below the front windshield drafts additional air into the interior along with more heat or outside cooling, not so good.

Volvo uses resistance wire in different combinations / sizes to drop voltage to the HVAC fan, each position on the fan switch is wired to one of these resistance wires ( high speed is direct to the fan ). The lead which powers the fan for continuous operation most likely comes off the ignition switch or a relay and is also wire to one of these resistance wires. If you locate the block with the resistance wires find the terminal with power to it when the ignition is on and the fan switch is off. All you have to do is cut the wire to this terminal and tape it up, the fan will now only work off the fan switch. ( note: make sure to cut the supply wire to the resistance block not the wire from the block to the fan ).

Tim

Dan-

I was sure that this was limited to the 200's but I guess I am wrong. But anyway....

On the 240's it is quite common for the earlier models to have this switch. The "0" is not actually an off position. The switch is designed to keep AC/heater components from freezing. I'm not sure if the fix is in the archives but once the other 240 owners see this... you will have your answer.

/// Check the archive. I remember post to the effect that what you describe is normal for some cars. There is some swap available but I don't remember that much of the exchange.