Heater/AC blower fan won't work on full speed

2007 Tacoma

Heater/AC blower fan doesn't work on high speed but works at lower settings. I inspected the motor and cleaned it out. There were no signs of arcing on any of the contacts at the motor. The motor does make and annoying ticking sound when running.

I removed the climate control panel and one wire connection at the switch was burned. It was burned enough to melt some of the plastic.

I have ordered a new wiring harness from Toyota and I've ordered a used but complete control panel from ebay. The replacement is very routine, but in brief search online I see this is common.

What is causing the overcurrent at the wiring harness? Is it simply a bad connection or is there something else going on?

I'd appreciate any and all advice from those of you that have fixed this problem.

And just so anyone asks, no it wasn't the resistor and I know that from a simple understanding of electrical circuits.

 

Most of the time that is from terminal fretting which eventually results in a poor connection, a bad connection creates resistance in a circuit which generates heat which further increases resistance and also weakens the spring tension of the terminal. That cycle keeps happening until the connection can no longer carry any current.

If you have a blower motor that is failing and drawing higher than normal current it can aggravate the issue.

This is one place I think Toyota could have done better with adding a relay for high speed instead of running all the current through the switch.

 

i vaguely remember an updated pigtail from Toyota in response to some techical bulletin. i did this, and i have had zero follow issues for about a decade. its been a long time.

 

That TSB applies to the resistor and pigtail, there is no updated switch harness or switch as far as I know.
I've been tempted to install a high speed relay on mine to avoid potential issues with the switch but I have yet to do so.

 

What was part number for the new wiring harness from Toyota? Thanks.

 

https://www.tacomaworld.com/threads...lay-mod-prevent-blower-switch-failure.827331/

 

Thank you.