Saturday driving up to work a car of mine I noticed the temperature gauge had not moved one bit up. I also did not have heat in the car. I took it to a friend's shop & he flushed out the heater core, hooked things back up. We ran it and gauge came up along with heat. Thinking everything was OK, I drove home. Temp gauge dropped and again, no heat. Is there a sensor that controls heater? TIA for any replies
Heater issues, this is strange...
steveshively669
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Saturday driving up to work a car of mine I noticed the temperature gauge had not moved one bit up. I also did not have heat in the car. I took it to a friend's shop & he flushed out the heater core, hooked things back up. We ran it and gauge came up along with heat. Thinking everything was OK, I drove home. Temp gauge dropped and again, no heat. Is there a sensor that controls heater? TIA for any replies
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Sorry, 1999 RAV4 2WD
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If you do not have warm air blowing in the cab, two thoughts I have are:
1) you don't have enough coolant
2) there is a problem with the temperature blend door (it won't divert to allow air flow from the heater core).
A bad sensor will not disallow heat to discharge the vents.
A bad temp sensor will control the needle position but it will not prevent heat from discharging as I mentioned already.
With that said, I don't understand some of the silly stuff Toyota does, perhaps the blend door is tied to a sensor but logically it doesn't make sense. That would be a first experience for me though.
1998 Rav4, manual transmission, 2WD, 5-door, JDM engine installed in 2013
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-- The heater does not have a temperature gauge to operate it. These Rav4s are pretty basic. When the driver or a passenger operates the lever on the HVAC panel, this mechanically opens/shuts a door to mix cool air with hot air as desired.
-- With the temperature gauge showing the coolant is not heating up, I suspect the thermostat is stuck open.
-- If you want to experiment a bit, carefully mount some cardboard in front of the radiator, to block air flow over the radiator. Does the needle on the temperature gauge rise now, or at least rise more than it was rising?
-- If you replace the thermostat, use only an OEM one or the Kuzeh one designed for the Rav4. The thermostat must have a jiggle valve, and the jiggle valve must be oriented correctly. If you need more info, post back.
-- With the temperature gauge showing the coolant is not heating up, I suspect the thermostat is stuck open.
-- If you want to experiment a bit, carefully mount some cardboard in front of the radiator, to block air flow over the radiator. Does the needle on the temperature gauge rise now, or at least rise more than it was rising?
-- If you replace the thermostat, use only an OEM one or the Kuzeh one designed for the Rav4. The thermostat must have a jiggle valve, and the jiggle valve must be oriented correctly. If you need more info, post back.
I agree on a possible stuck open thermostat. Another test for that is letting the engine idle for maybe 10 minutes. If the gauge comes up and you get at least a little heat with no air flowing thru the radiator, but it all goes cool when you drive creating air flow that pretty much confirms a failed thermostat.
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I also agree on a stuck (or sticky) thermostat. Better to stick open than stick closed!
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a purge funnel is a cool must have tool
when filling the cooling system.
it helps with the air pockets and long run time to fill the system correctly.
No Spill Coolant Funnel Kit
that is the low cost version (22.00 shipped)
it works well so you can leave the rav run till the thermostat opens
and keeps the system at topped off.
and has a funnel plug to save the antifreeze for a few tablespoons lost.
i would check the system for coolant loss.
and do a cyl leak down test to check the head gasket.
what does the engine oil look like?
when filling the cooling system.
it helps with the air pockets and long run time to fill the system correctly.
No Spill Coolant Funnel Kit
that is the low cost version (22.00 shipped)
it works well so you can leave the rav run till the thermostat opens
and keeps the system at topped off.
and has a funnel plug to save the antifreeze for a few tablespoons lost.
i would check the system for coolant loss.
and do a cyl leak down test to check the head gasket.
what does the engine oil look like?
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Depending on the length of drive, the vents should still blow warm air even with an open thermostat. Unless Toyota has a super cooling system. I've had open thermostats in the past and get warm air discharge from the vents. Just no experience with Toyotas that may be different.
It will take longer to get the coolant warm enough to feel the discharge air temperature change but it should be warmer than when first starting.
This is dependant on outdoor temp, if it is warm and you're trying to take the edge off by running the cabin heater, you may not feel much of a change if you drove short disance, longer distance you should notice it. If it's near freezing lets say, the coolant may have a hard time getting warm enough to feel the warmer discharge air.
What was the outdoor temperature when you experienced no heat in the cabin?
If the thermostat is stuck open and you can't feel warm air, the car should return a code for not reaching normal operating temperature. Usually a P0128 code.
It will take longer to get the coolant warm enough to feel the discharge air temperature change but it should be warmer than when first starting.
This is dependant on outdoor temp, if it is warm and you're trying to take the edge off by running the cabin heater, you may not feel much of a change if you drove short disance, longer distance you should notice it. If it's near freezing lets say, the coolant may have a hard time getting warm enough to feel the warmer discharge air.
What was the outdoor temperature when you experienced no heat in the cabin?
If the thermostat is stuck open and you can't feel warm air, the car should return a code for not reaching normal operating temperature. Usually a P0128 code.
1998 Rav4, manual transmission, 2WD, 5-door, JDM engine installed in 2013
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1,214 Posts
I have doubts that U. S. distributed first generation Rav4 computers are able to generate a P0128 code. At least, P0128 does not appear in the 1996 Rav4 diagnostics section that I have. The P0128 code has been mentioned in only one first generation Rav4 thread here, by two different Canadian Rav4 owners.
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