lululalalu

Sometimes the blower motor fan slows way down.

I suspect the HVAC relay. It is located up under the dash. You have to remove the glove box to access it.

I have two OEM relays. When I switch out relays, the fan speed returns to normal for a couple of weeks.

Btw - The resistor that controls fan speed located way up on the passenger right foot area is new and good.

1. What is the purpose of this relay?

2. What is going on when I have very low fan speed?

3. Why does switching out the same relays fix this for as short time?

4. If the root problem is causing the relays to do something weird, can I just shim or block relay contacts some how so the fan will always blow full blast when on high?

Thank you,

scope103

The relay has nothing to do with the fan speed control; it's just there to keep you from switching a 30A load with a tiny panel mounted switch. http://personal.utulsa.edu/~nathan-b...g/25heater.pdf

I would suspect that the blower has "crap" in it, or that the motor is reaching end-of-life (which could be due to said crap). That would cause it to run slow intermittently. It would also cause it to pull more current, which might be welding (or otherwise over-working) the relay contacts. Putting in a new relay with new contacts might help until the overload works them too.

I'd pull the motor to look for dirt in the blower. While you are at it, consider pulling the cooling unit; it's before the blower, so if you have dirt in the heater fan the evaporator is probably a mess.

lululalalu

Thank you.


I pulled the motor and it was clean.


I put power directly to it while removed for a fairly long test and it ran fine.


Any suggestions on what to try next?

RAD4Runner

Inspect wiring for high-resistance contacts (hence bad) that get hot with use and whose resistance increases with temperature.