Can a faulty blower motor resistor cause electrical gremlins?

My blower runs, but as I increase the speed the engine rpm drops to as low as 480 in gear stopped at a light. If I shut the engine off when warm, restart 5 min later, it’s fine. Does that make sense?

 

What happens if you turn the blower off?
Does idle return to normal?
Or do you have to turn the truck off to get back to normal idle?

My truck idles about 550 in gear.
What is your normal idle?

 

When I turn the fan down to either 2 or 1 on the speed control, idle returns to normal.

As for the second question, I’ve had this for so long, I don’t know the “normal” idle speed. I do know, when I turn the fan to high, idle in gear is anywhere from 480 to 530rpm. I only caught it today at a light. because I changed the fan speed while waiting. According to my scan gauge it was 483. Turn the fan down, it went to 562. This has been a problem for about 10 years.

 

First thing I would check is how dirty the throttle body is, it could just be so dirty that the PCM is past its idle airflow compensation range and as the electrical load increases it can't raise the idle anymore.

 

Wrong thread?

 

Yeah. Wrong thread.
Opened the wrong tab.
Thanks for catching it.

 

Cleaned the TB twice in the past year. Maybe 15k km’s since. Disconnected the neg battery cable for at least 30 min. No difference.

 

Is it just the blower?

Does anything change if the headlights are on and on High?

 

Just the blower. I did change the under hood fuse, and the fan speed went up. Fuse looked a little dark and blackened.

As well, year old Northstar 27f battery and Mechman 240A alt. Verified with clamp, puts out 254A at 1500rpm.

 

A problem in the blower circuit should not affect engine operation, I suspect you have a main power or ground problem.
Do you have the V6 or the 4cyl engine, is your check engine light on?

 

V6. I’ve never had a check engine light. I’ll look into the power and ground situation. Keep the tips coming too.

 

Toyota engines are notorious for idling super low when warmed up. Sounds like you don't have any starting/charging issues, the engine never stalls, no check engine light..

I wouldn't worry about it honestly

 

Looked into the power and ground situation today, as it’s almost at freezing. Poking around on the fuse box in the engine bay, I traced the wires. About 15 years ago, I did a big 3 upgrade. Comparing to the big 3 sticky in this forum, I looked around. I hadn’t reconnected my alt->fuse box wire, IN 15 YEARS! Thanks to @Dm93 for suggesting this course, and @TnShooter for being patient with me.