Need some guidance diagnosing strange climate control problem

Hi all, looking for some help diagnosing a strange problem on my '03 taco. The air conditioning works and blows cold air but will start blowing hot air after a few minutes or seconds. If I turn the temp dial from cold to hot and then back to cold the ac will start blowing again for inconsistent amounts of time and then go back to hot like its defaulting to hot. The ac charge levels are good, no leaks. Any ideas?

Thanks!

 

Could be a compressor clutch going bad. See if it visibly dis-engages when the A/C 'shuts off'.

 

Thanks for the reply. Clutch engages when a/c turned on. Does not disengage until a/c is turned off. Still intermittently goes from cold to hot. Sometimes it will blow cold for 10 min or so and then just go hot. Could it be the climate control panel electronics?

 

How did you check the refridgerant level?

 

R134 needs airflow over the condenser to properly draw the heat from the refrigerant passing thru it, check that your clutch fan is operating properly,

DO you have this same issue when the truck is moving down the road at speed ( over 20 mph )

 

Sounds more like a blend door issue to me

Us there a vacuum leak that us preventing the blend door from staying at its setting?

 

i second the blend air door, check to make sure the motor is not broken or the door where it engages the motor.

 

Clutch fan is operating properly, refrigerant was checked at a tire shop. (they seem to think it's the electronics in the climate control module.) that part is pricey though and don't want to buy one blindly.. Blend door sounds like maybe that could be it. How do I check it? Also, I had the Dash apart today looking at the connections and climate module area. This time it would go back and forth from cold to hot. It didnt go back to cold before on it's own.

 

take the glove box out and look for the actuators/motors that operate the blend air doors, switch the dial from hot to cold and see which motor moves,look for any problems in that area, you can remove the actuator and see if it is cracked or broken where it connects to the door, with the actuator off move the door by hand and verify smooth operation, if tha all looks good it could be the controller.

 

another thing you can check is making sure the heater control valve is working properly. get it going cold, disconnect the cable from the valve, and see if it still gets hot.

 

What was the outcome?
I have the same sort of issue. When the AC is on, sometimes the heat comes on.
I can make it cold again by move the temperture dial to Max heat and back down to cold.
The the heater will turn off for a while. It does the same thing when it on the heater setting.
The temp will switch to max heat, if you move the controll to max heat and then return it to the propper setting it will work OK for a while.
Then it will switch back to max heat.

Whats wrong with the system?

 

Thank you all for your very helpful suggestions. I truly appreciate you taking the time to help me out. After checking everything else, it boiled down to the control unit being faulty. I had the dash apart after checking everything else and accidently found that moving the control unit around and putting slight pressure on the boards (plugged in) that I could make it fail and come back on demand. Being an electronics guy I assumed this was a cold solder joint or short circuit somewhere. The unit comes in two parts, the control head and the amplifier. I wasn't about to pay Toyota $550 for the set so I took it out, took it apart and freshened up (re-soldered) most all of the major solder connections for the dials and ribbon cable. Installed back in and so far working properly. I just did this today so I'm not positive the fix will be lasting. I'll report back here in a few days or so when I have some confidence in the solution.

 

Been 2 days now.. Still working great.

 

congo-rats!!! love it when people are capable of doing stuff like this rather than just buying a part when unnecessary. have you seen that guy whos frame was over 50% deteriorated from rust and just re-welded new plates on there, perfectly repairing it, as though it was nothing? that's awesome......

 

Thanks for the reply!

 

Still working perfectly! I'm pretty confident the issue has been solved after months of sweaty hot days and frustration. Happy Days

 

Have same issue w/ my 2003 taco d-cab. Having a problem locating part number ... do you know what the part number is or what it's called ?

 

Welcome to TacomaWorld
HVAC Blend door actuator

 

I'm 93.4% sure this is my problem. Same sporadic behavior of the actuator motor (replaced) and still only moves 1/3 of the time. I've found the part (heater control module) ranges from $100-200 on eBay. How likely would I be able to find the soldering that was bad? I'm considering going after this the same way that cheddardonkey took. I'm not a soldering expert, but I can do enough to be dangerous.