Erratic blower fan speeds. Help please

2010 Tundra SR5 HVAC blower inconsistent speeds when on high. Replaced the blower fan assembly with an aftermarket and doing exact same thing. Where would I go from here? A relay? Or replace the dial on dash / switch? Thanks in advance.

 

Check the connector to the blower motor… make sure there is no corrosion and is fully seated.

I would suspect the blower motor resistor, but I don’t think the 2nd gen has one, meaning speed is controlled by the HVAC amplifier (control unit). I would definitely want a good diagnosis before throwing parts at it.

check out post#5 for diagnostics: https://www.tundras.com/threads/ac-amplifier-replacement.75065/

 

Thanks for the reply. I checked the connector. It appears to be free from corrosion. It looks like the resistor is built into the blower fan assembly itself. I guess I could buy a 3rd one to see if I possibly purchased a faulty new aftermarket. But it is doing the exact same thing as the OE blower fan. When I place it on the upper speeds or close to high, it will become erratic and change speeds.

 

Check out this thread about upgrading to a Land Cruiser brushless motor: https://www.tundras.com/threads/hvac-blower-fan-upgrade.135617/

 

Feed the old one juice directly from the battery with jumpers, probably nothing wrong with the motor. Which means wiring, switch, control unit, etc.

 

https://www.tundras.com/threads/ultimate-tundra-wiring-diagrams-collection.81448/

 

When I wiggle the switch on the dash, I feel like I can sometimes get the fan to change speeds. That gives me the indication that it might be in the fan speed switch. Looks like might have to buy the entire control unit to get that switch. Am I seeing that correctly?

 

How good are you with a multi meter?

Do you have automatic climate control (where you set temp) or just cold-hot variable knob?

Like 2mchfun suggested, bench test the blower motor by feeding with direct battery power (with engine running). Bonus points if you can get a current (amperage) reading; it should be consistent while running.

 

My fan speed switch is manual switch vs the automatic climate control. Unfortunately I do not have a multimeter, but I could buy one .