Heater Quits After A Couple of Hours

Recently my wife and I drove about five hours to a relative's house. The outside temperature was in the 30s. My heater worked fine for a couple of hours, but then it began producing lukewarm air. An hour later my windows became covered with condensation. By the end of the trip we were freezing and could barely see out the windows. I had to roll down the windows for awhile. The same problems occurred on the drive back home.

In the summer my A/C also cuts out after driving a couple of hours.

I took my Tacoma to the local dealership, but they weren't able to find the problem. Does anyone have any idea what is wrong?

Thanks.

 

I thought I tested every combination of the heater controls, but I forgot to check the recirc/fresh air switch. Considering the condensation the air might have been recirculating. The fan worked fine in the beginning, but after a couple of hours it seemed to stop. I don't think I tried it on high.

 

I have an 05 sport with around 165k. My fan also would stop from time to time. I found a good firm smack to the blower motor near the underside of the glovebox gets mine going again but I'm sure that will only last so long. I've also learned that the fan control switches are prone to going bad. The switch wasnt engineered to be used the way toyota implemented it though I haven had one go bad yet.

 

I did search the forums and found references to the motor blower resistor. I plan to call the dealership tomorrow and ask them whether they checked that.

Does anyone know whether that's a possibility?

 

First check to see if the blower is running.

You may have an issue with the thermistor that controls when the compressor turns on and off. In some modes ( even when heating, such as defrost mode ) the A/C runs. If the thermistor is not cycling the compressor the Evaporator Core will freeze up and block the air flow.

 

As above if resistor, blower, and AC all work OK there is a heater control circuit card located behind the glove box then pull the upper plastic face piece out (1 screw right on the latch) and its mounted way up high to the passenger side on the round cross member with 1 screw on top and a large bunch of wires running to a plug in near by. Found it looking for my door remote card and ran the part #. The card is in the plastic box that you see and can take out. If the plug in connector has shaken loose it could effect the heater controls (when I pulled mine out to look at it and reinstalled it took a hard push in to get all controls to work again. You will also see the ECU back there vertically mounted near the kick panel. This a long shot as probably one of the other items but just so you know about it.

 

Have you checked the coolant level?

 

Thanks you guys. I really appreciate the help. I called my dealership, and the technician said they checked the resistor. His opinion is that there was an air pocket in the hoses leading to the heater core (or something like that). He said they did bleed the hoses. So now I need to take it on a long drive to see if it's fixed.

One thing I didn't mention is that the light on the fresh air/recirculate button is too dim to be seen. I can't tell whether I'm using fresh air or interior air.

Thanks again for all the help.

 

IIRC the recirculate will turn off automatically when the truck is turned off. When you go for a test drive, don't push the button. Also note which mode the selector is in. Leave it on vent/floor, unless the windshield is fogging, then run defog only long enough to clear the windshield. This info will help with diagnosis.

I doubt an air pocket was the problem, but

 

Also, if the problem happens again, pull over and pop the hood. Check the metal lines at the firewall from the AC. If the evaporator is freezing up, the larger line will have ice on it. If it has ice, it's what jimmyh said about the thermistor.

 

That's more great info. If it weren't for you guys I would never be able to get this fixed. I'll take it out for a test drive soon.
Thanks

 

Mine does that too. I have to reach over and jiggle that wire harness and it cuts right back on. Or if someone is riding with me, kick up with their left foot. Goes out every couple days. It works on 'high' all the time.

 

https://www.tacomaworld.com/threads/fan-speed-switch-not-working.70275/

 

I took Curt's advice and went for a drive. For 70 miles outbound I had the fan on low, the thermostat on high, and mode on dash/floor. The outside temperature was in the 40s, and the heater put out a ton of heat. So much so that I had to open a window part of the time. On the way back I left the first two settings alone and switched the mode to defrost/floor. After that the heater air was lukewarm. That combo only produced about 20% as much heat. Is that normal?

On the drive I described when opening the thread I'm sure I was using the defrost/floor mode most of the time, because that is what I normally use.

 

It’s sounding more like this^

 

Curt even said how to check the thermistor, but I totally forgot. I'll check it as soon as I can.

 

When sitting and parked run the AC System on Max Cold. Open the hood and monitor the AC Clutch. It should kick on and off on a regular basis as the evaporator gets to the set temperature it should turn off until the temperature rises above that set temperature... over and over.

This is what prevents the evaporator core from freezing into a solid block of ice.

 

When you switched to defrost/floor, how long did it take to notice the heating loss? Fairly quickly or a long time? And check all fan speeds when the heat loss begins. You should be able to hear the higher speeds. Turn your music off.

 

If that cough persists, you should see your doctor.

 

The AC is on when in defrost/floor mode.
IF the evap is frozen up, air flow will stop. By changing the fan speed to high, he can hear the sound change. This would tell us whether the fan is quitting, or not.