hot air comes thru vents

hot air comes out vents when ac/heater is off the selector is in cold position. change the servo motor what else can i do 2002 tacoma 2.4 engine extcab 4wd

 

When you turn on the AC, does it blow cold then?

 

That is not unusual, even in the s10 this is a problem. I can't remember what the fix is in the s10, but I do remember it was simple. I just turn the a/c on with the interior circulation on, then just turn the fan off. This most of the time takes care of the problem. If you had the heater or vent on last before shutting the fan off then a little hot air comes through the vent. Nothing pointing it the other direction or cracking a window for a few seconds can't fix.

 

i have the fan off, ac/heater off, and the selector in cold position. Feel like the heater is on with hot air coming out. when ac is turn on, hot air still comes out

 

no it still blow hot. air ac works

 

Check your blender door, its the one that controls the hot water going through the heat exchanger for hot air, if it stays open then you always have hot air.

Its on the firewall in the middle with a cable attached to it that controls the flapper valve. Check that, not sure if you meat that was the "solenoid" or not.

If so then check the cable, maybe its not actually moving the flap door.

 

I feel like every car I've ever owned leaked a little air through the vents when the fan is off. But I could always control the temp of the air with the temp control

 

From what I understand you're saying that air comes through your vents even when the fan is off?
Try flipping the switch that allows air to be drawn from inside the vehicle rather than outside (Idk what that switch is called) Mine only has air coming out of the vents when air is drawn from outside the truck.

 

i replace the servo motor (which control the hot air/cold air). it stays in the hot air. it won't move to cold air. do the servo motor has to be calabrated.

 

Do you have a temperature blend door? Or a coolant bypass valve? There could be a little valve near the firewall in the engine bay, on one of your heater hoses. See if the valve is closed or open. And if it works correctly when you change the temp.

 

I fixed the same exact problem by tweaking that valve on the firewall that controls coolant flow to the heater core. From the engine bay, you can see the valve turn on/off when the temp knob is turned from hot/cold from the cabin. Unscrew the moving arm on the valve and make sure its making good contact because the plastic surface on mine degraded causing the arm to loose control over the valve leaving it stuck open. Reinstall the arm and make sure the philips is tight.

 

I discovered this "trick" recently. I was having the same issue: with the fan set to off, a small amount of air would still be coming through the vents. By switching it to recirculated air (vs. fresh), it would all but eliminate any air coming through, even with the system set to "off".

 

There is always 20% fresh air entering the cabin even on recirc.

 

I had the same problem. I read this thread and decide to look under the hood. Found out that the cap to the coolant reservoir has been open since I last topped it off. I closed it and seems to be normal. I was also noticing that the face of my stereo was super hot and that too is now normal.

 

a lot of the heater valves are vaccum operated but on our trucks its cable operated so no need for ways to turn it off, on is on and off is off.

look under the hood and in the center of the firewall you will see a little black box the heater hoses run to before going into the truck, that is what turns the heater on or off. yours may be broken or disconnected so check to make sire the cable moves and moves the valve, if it does then take the hoses off and see if it really closes or not, it may have trash blocking it from closing or its bad.

 

Tagging on with same problem but seeking opinion and help. I have a 2004 DblCab, last spring 2014 I noticed now matter where I rotated the center temp dial it randomly moved the heater blend door, mostly stuck on full hot. In frustration I removed the cable harness at the passenger footwell ahead of the servo once I had the door randomly select full cold, motor disengaged at that point and door set to cold..that was to get through the summer without blasting heat into the cab. Now it is winter, I would like the heat back, and of course I still have the problem. I took apart the dashboard since I had several dash lights out (I very thankful to other posts on how to take the dash apart, lamps replaced) one of the lamps was to the climate control center knob. I noticed there are 2 circuit boards that are connected by thin ribbon cable. Is there any speculation that the circuit board is faulty? I don't see any way to replace the temp dial itself part of the circuit board. Dealer parts is $175-$300 to replace those small circuit boards. I've seen high quotes elsewhere to dismantle the entire HVAC system and 2 TSB on later generation Tacoma with blend door malfunction. I've seen junk yard postings for the climate control boards that I might try. The servo motor is working and the blend door moves - it just won't follow the knob control at the dash. Thoughts?

 

my 1999 has no circuit boards at all, just a simple no fail cable operated heater valve so if yours has a circuit board control in it, then its obvious not all first gens are the same

 

Did you do anything to the controls in the dash?

I had the same problem after replacing some light bulbs and it turned out that I didn't fully reconnect the wiring harness to the dash controls. If the dash controller is disconnected, it defaults to heat.

 

2004 last year of gen 1 per the chart. I purchased 4 bulbs at Toyota Dealer, side marker light, climate control temp bulb, 2 bulbs on the tachometer, all that worked out well. I figured while was at the effort to dive inside the dashboard dismantle, I might as well take a deeper look into the climate control cluster, 3 screws take that all apart, then that cluster splits in 2 more pieces with separate circuit boards. My blend door is intermittent to respond to playing with that rotational center heat knob, it's a bit of a game while driving to trying to find a position on the dial where the blend door will move away from full heat somewhere midway, otherwise no matter where the knob is, it must default/jump to full heat. My summertime fix was to wait until it randomly hit cold then I immediately yanked out the power cable to the servo and it stayed at cold all summer no problem and I could still run the A/C fine. Now the temps are colder so I want a mix of heat on the way to work. I haven't done any search yet to see if anyone replaced that climate control cluster. I was told the front part of the cluster is $175 and the back half was $300, reminds of the cost of replacing parts on my old VW. I don't have to worry about the cold as I can always get full heat and drive with window open but in Seattle it rains all the time, so hot, cold air, then all wet. Apparently the 2nd gens had the TSB's with some defect with the blend door itself and there's detailed pdf files here of the more challenging teardown to pull the entire hvac system out to get at the blend door. Of all things such an annoying problem to tie to a dozen electronic circuits if that is the case. I found some salvaged climate control clusters, I may have to try that route and see if that solves the problem.

 

Jut joined.

Charles3, I think that I had the same problem as you. Basically the response of servo motor that operates the mixer assembly was inconsistent with the control knob setting. Invariably, the servo would select the hottest position despite the fact that the knob was set to colder or coldest.

This appears to be a common problem based on other threads / forums.

The root cause appears to be dirty contacts in the control knob component or board; this results in a high resistance being presented to the servo motor circuit for some control knob settings which in turn is interpreted and processed as a GO HOT request.

The fix that worked for me was to clean the 2 boards and the control knob with DeOxIt (an electrical contact cleaner). I also pulled out the ribbon cable that connected the boards and carefully cleaned the ends there.

Of course, you could have a more serious board failure, but I would try this cheap fix first. It's working like new for me now. (Perhaps you have fixed this already)