Blower Speed 4th Issues

[SAYaris2013]

Blower works fine on 1st, 2nd and 3rd speed, when switching to 4th speed, it sounds like a switch is clicking under the passenger dashboard and fan clicks on and off. It’s definitely electrical, because the all the switch lights flicker.

[FROSTYBALLS]

Moved to the Yaris club.

[flash22]

That's a bit odd, Blower motor resistor seems the logical fault, check the cabin filter is clean and clear of debris

[Bernard Foy]

Check out if the motor fixing has not worked loose providing a bad earth at the higher speed.

[Starensis]

Speeds 1-3 are via a resistor, 4th speed isn’t. Sounds like the speed control switch - contact issue?

[flash22]

15 hours ago, Starensis said:

Speeds 1-3 are via a resistor, 4th speed isn’t. Sounds like the speed control switch - contact issue?

The switch sends a signal to the AC amp it sends a PWM signal to the blower motor "resistor" (it's more of a transistor pack) this controls the motor

[Starensis]

On 12/29/2021 at 11:49 AM, flash22 said:

The switch sends a signal to the AC amp it sends a PWM signal to the blower motor "resistor" (it's more of a transistor pack) this controls the motor

OK, but think my point was, 4th speed is a bit different to 1-3. High speed doesn't usually use resistor.

[flash22]

The motor is still controlled through the "resistor pack" the 4th setting has a thermal PTC fuse, internal in the pack (usually the PCB's are potted), that doesn't affect the other speeds

The lack of airflow across the pack and repeated heat cycles eg. A blocked cabin filter will cause it to overheat and fail over time

 

Edit. Thinking about this and the OP hears clicking, it maybe a faulty/loose blower fan relay and/or fuse that is not able to handle the current at full speed

[flash22]

R/B No. 4 - HTR relay is behind the glove box up high above the internal fuse box

90987-04010

[SAYaris2013]

Thanks all for advice. I will check these out over the next few days and get back with an update.🙂