Hot/Cold Temperature Dial not working

I have a 2005 TRD manual shift 4x4 Tacoma

The hot/cold temperature dial works intermittently. I start the truck in the morning to warm up and set the temp to high to defrost the windshield. I come out after 10 minutes and have nothing but cold air blowing on the windshield. I fiddle with the temperature dial, moving it from hot to cold and it eventually starts flowing hot air into the cabin.

I took it to my mechanic this morning and he says it's working fine and can see no reason for my symptons. He suggest I wait till it completely fails to then find out whats wrong. I don't like this solution with winter rushing rapidly towards us in upstate NY.

Any suggestions on what to check out or what could be the issue and fix?

Thanks!!!

 

I know if I start my truck in the morning and it doesn't move, it takes a while for it to get warm. Once the engine starts moving though I'd say about 3-5 mins it starts getting warm

 

Thanks for the feedback but that is not what I was asking about. My engine warms up okay. I am not asking about how long it takes for my engine to warm up.

In the cab the dial that you turn on the dashboard is not changing the temperature inside the cab. Any ideas on what could be wrong with the temperature dial on the dashboard.

 

I understand that. I was saying my heater doesn't kick in until my engine starts moving other than idling.

 

I ran into this today with a highlander at work. is the dial itself loose? if it is, there is a bolt behind the knob that may have come loose. pop the knob off and tighten the bolt.

 

Thanks, I'll check. I removed the whole console and disconnected and reconnected the plugs, but it had no impact.

I checked the temperature of the heater hoses going into the heater core and only the top one was hot. The bottom one stayed cold to the touch. Any thoughts on what to do next?

 

Sounds like your heater core may be plugged. You may need to unhook the heater hoses and flush out the core with water. If that doesn't work the only other thing I can think to try is seeing if the temperature door actuator inside the truck is operating normally when you turn the knob on the controller.

 

Thanks! I was going to flush the heater core and see if that did anything.

Where is the temperature door actuator located? I am not seeing anything about it in my Haynes repair manual.

Thanks,

 

I got this from Mitchell On Demand.

 

Turn key position "on" without starting engine and keep windows up/radio off to hear the noises.

Then start the fan, if everything works correctly you should hear a sound change when turning the dial from cold to hot.

Hope that helps.

 

The fan works fine moving air at all speeds.

I'm going to flush the heater core today and will update you all on how it turns out.

Thanks to all for your feedback!

Cold temps due in western ny this weekend so I need to get this fixed pronto!!

 

Success!!!!!

I flushed the heater core at lunch. I ran water through a garden hose through both lines about 4 times each till the water ran clear. Really wasn't to much discoloration. I then took off the radiator cap and put a funnel half filled with fluid in the radiator top and ran the engine for 20-30 minutes to get any trapped air out.

I turned it off and let it sit till the engine was cold then started it up and switched on the heater to warm the cab like on a cold morning. I went in the house for a sandwich and came back 10 minutes later and was met with nice warm air flowing through the vents. I am now ready for winter!

Thank you all for your help! This forum is always a great resource for me and helps me avoid going to the dealership or local mechanic.

 

Ok... dumb question, which two lines? I was looking at it this morning.

Are they the two going through as high on the firewall as possible, between the master brake cylinder and engine?

Do you disconnect both of them at the firewall and run the water into the cab that way until it came out of the other line clear? So, you ran water forward and backward through the system?

First time really haveing to screw with the heating system on any of my vehicles, so I want to make sure... was thinking of just topping it off to get air out of the system first... especially, since you didn't really have any discoloration.

Thanks in advance!

 

They are high on the firewall on the driver side. I'll snap a picture and post it when I get home. I disconnected both hoses and ran water through the top metal tube first till it ran out clear through the bottom line then ran it through the bottom metal tube till it ran clear coming out of the top line. I repeated this 4 times for each line just to make sure it was clear, then ran the engine with the radiator cap off and a funnel with fluid filled half way up the funnel to burb out any air bubbles in the system. Did this for 20 minutes or so. Works great now.

 

Glad to hear it cleared it up!! This is the method I prefer but I was wondering if a coolant flush would have produced the same results? Anyone else?

 

I hope to try this over the Holiday weekend. I'll post my results... good or bad!! I love these forums! They are very informative, and help solve issues without dealerships!!

 

Here is where the heater tube inlets are at the firewall for the heater core.

In regards to a coolant flush. I had one done 1 week before this issue started while getting my new tires put on. I think that this is what caused my issue with the heater core. Next time I do a coolant flush, I am going to flush the heater core as well.