95 A/C Blower Motor Won't Turn Off

[sebvox]

I was driving down the freeway (with the A/C off) and the car in front of me had bad exhaust, so I hit the recirculate button, out of habit. Now the blower motor is always on. Hitting the "off" button does nothing. I ran the self-diagnostic for the A/C with no faults. I have disconnected the battery to no avail. Bad climate control panel?

[maxnix]

Probably. Very rare on the later Q45, provided the owner exercises the unit regurlarly the year round.

[MinisterofDOOM]

Is the motor stuck on high speed? If so, it's probably the variable blower resistor (aka darlington transistor or blower amplifier).You can pull one of the two interior climate control fuses and it'll kill the blower.

You can pick up the resistors from junkyards for a few dollars apiece. Most Nissan/Infiniti models from the same era will have the same part, so I'd just go snag a handful of them from your favorite junkyard. You need to remove the glove box to get to the resistor, but it's a simple matter.

[Q45tech]

Important to understand WHY the transistor assembly fails FROM a worn out fan motor that is drawing beyond design point current.

As electric motors wear out they turn slower and draw more current, evenyually this extra current grossly overheats the transistors and they fail creatinng an open circuit in the assembly.

The HVAC ecu senses this and command the high speed relay to close as a warning that the transistor assembly has failed and as a fail safe to maintain air flow.

HVAC fan motors have a ~~ 10 year life by 14 years they almost all fail, of course depending on hours of use.1 hour per day 365 x 14 is 5,000 hours. 2 per day is 10k hours.

[sebvox]

Thanks! Just ordered a new blower motor and planning a trip to the junk yard for the fan control amplifier.

[sebvox]

Just a follow up-

I needed to turn the defroster on whiel it was raining the other day, so I pressed the defrost button. When I got in the car later, I hit the "Auto" button and noticed the fan was not on high anymore. So I hit the "Off" button and it turned off. Problem fixed... for now.

[bigdog76]

I would have started by just replaced the darlington resistor.I changed that 3 years ago and my blower is still running fine now.Its up to you if you have the money to throw down on the blower.