I have a 2001 RX300. The heater is not working. It just blows cold air. The temp. guage shows normal running temperature. Before having the thermostat replaced, is there any other cause I can check like a fuse, etc.

Coolant level is full, temperature guage shows normal, blower works fine, no visable vacuum lines disconnected, radiator is clean, no build up on front.

Any suggestsions??

Thanks

 

Do you get cold air (with ac compressor running) or you are getting no heat.

The heating system is based on
circulating engine coolant throught a heat-exchanger.
Fan blowing/recirculating air over the heat exchanger.
Ducts controlled by various flaps to channel air flow.
Electronic thermostat [desired cabin temprature]

The cooling is all of the above + ac compressor with refrigerant loop.

You need to ensure that cooling is shut off (ac compressor not enabled and or refridgerant pipes not being chilled).

Then observe fan is working (move out of auto if required)

Heat exhchanger getting heated coolant is hard to diagnose without disassembling. May be some one can post which pipes to monitor from the engine block. [I would suspect trapped air if some one worked on the plumbing , engine-thermostat etc...]

Does your temp gauge move to middle within 15~20 minutes? If not your engine-thermostat is bad and you will not get good heat inside as the coolant is not getting hot enough. From your post it seems that it does, so replacing the engine-thermostat will not make any difference.

Ducts are elctronically controlled and you may have a problem with certain solenoids or even with the brain [ecu]. You can try power cycling the ecu by disconnecting the battery for 15~20 minutes. On old cars (specially when ducts are not operated) the flaps can get stuck and the solenoids dont have enough oomph to pop them.

Electronic thermostat which governs the fan speed in auto. Try setting to hot and observe a change in fan speed.


Happy hunting.

Salim

ps: I dont think that the ducts are controlled by vaccum line in RX. If some one knows for sure, please post.

 

That’s correct the RX does not use vacuum lines. It appears that the servo for the air mix door is stuck. I would recommend disconnecting and reconnecting the battery to see if the system will reset itself. One other point, having the A/C compressor button engaged does not prevent you from getting heat. On the contrary, I never run heat without the A/C engaged as it removes humidity from the air and keeps the windows from fogging up (regardless if it’s on fresh or recalculate).

 

The A/C works fine and blows cold. The fan works though the settings of low-high.

With the heat dial at 80 it blows, but does not get hot or warm. Fan still works low-high.

The temp guage does go to normal driving temp after a few minutes.

Are there any fuses that control the ducts or solenoids.

 

Alsalih on 10/26/06 referenced this posting regarding the servo motor in the ventilation system..

http://us.lexusownersclub.com/forums...howtopic=20561

 

OK............last night I disconnected the batter for about 5-10 minutes. Reconnected and started the vehicle. The blower runs just fine from high to low. The engine warms up to normal driving temperature.

I went through the different settings on the A/C and heat. Defrost, floor, floor-cabin, etc. The duct (flaps) all workd fine, directing the air to the correct places. The blower did change with each different setting. It blows harder in a few settings and a little slower in others.

Coolant level is full.

Any other suggestions.......PLEASE (fuses, hoses, solenoid, thermostat, etc........???)

 

You did not state the temperature was set to "MAX HOT" after the engine had warmed up.

Is the A/C LED switched turned off?

I show Fuse #32 as a heater fuse
(15Amp - not the blower fuse, #50)

You get no warm air out of the system vents?

 

Good point Tammy, make sure the heat is set to max heat, having at 80 does not guarantee you will get warm air. If you’re still not getting hot air then it could be that have you air in your system after doing the thermostat replacement. You’ll need to purge the air out of the system.

 

The A/C LED switch is off (not lit up).

The heat setting is at max or "HOT" with the engine at normal running temperature. (warmed up)

NO HEAT from any of the vents.

What does fuse #32 do? as for as the heater goes?

 

PLEASE........having the heat set at 80 does not guarantee you'll get warm air....at 80 you should get HOT air.

AND the thermostat has not been changed YET. That was one of my questions, Do you think it is bad or stuck open.

SOOOOOOOO there is no air in the system to purge out.

Give me another solution.


People........I know how to turn the HEAT ON. I know to let the vehicle warm up before expecting warm air to be blown out of the vents. It was also stated earlier that the A/C being on with the setting at 80 or HOT does not effect the air not blowing warm.

Any other guesses out there?

 

The amount of warm air coming out will depend on several inputs into the control unit, which includes the outside temperature, inside temperature, etc.. Therefore under certain input conditions you can have the temperature set at 80 and only get slightly warm air, setting it to max heat will bypass all the inputs and provide max temperature.

If the thermostat was stuck then your vehicle would quickly overheat, sorry I misread that to mean that you had just replaced your thermostat.

Regarding the A/C being on, try it on any other vehicle you have if you don’t believe me. Set it to max heat and keep the A/C button on, you will get hot air!!

Good luck

 

I live in the south, it has not hit winter temps yet, but we have had a few cold nights in the 30's and 40's. I have tried the heat with the A/C on (LED lit) and the A/C off (LED not lit). Neither helps blow warm or hot air.

I do not believe the thermostat is the problem. If it was stuck closed, the engine would overheat. If it was stuck open, the engine would never really warm up. The coolant would never heat up to normal driving temp. I thought this might be a fuse problem or something else I may be able to fix myself, before taking it to the stealership to be fixed. The problem is probably something simple and will cost me a few hundred dollars at the dealer.

 

What I actually meant was that on a vehicle which has a working heater, it doesn’t matter if your a/c button is on or off, obviously in this case its not relevant. One last thing to check is the coolant level in the radiator, regardless off what the reservoir is showing. You could have a low coolant level in the radiator and because of a bad radiator cap you will not know it. When the vehicle has COOLED carefully remove the cap and make sure it’s full of coolant as a low level in the radiator could deprive the heater core from coolant yet not impact the vehicles operating temperature. Please update us on the findings even if it ends up at the dealership.

 

By now you have reassured yourself that both AC and heater on still does not produce hot air.

The next thing to verify would be to see if the coolant (heated) is making its way to the heat exchanger. I am assuming this to be a side loop and you can get trapped air, from preventing coolant flow. Clogged pipes seems very unlikely.

I think you need access to service manual to identify the rubber pipes leading into the heat exchanger. One can guess by looking at the plumbing leading to the front passeger corner (guess). Maybe there is a electronic valve in the coolant path.

Once you identify the pipes, you will need some sort of plumbing fitments + pipes to observe coolant flow. Be careful as the coolant can be scalding hot and the pressure will be high to increase boiling point.

Without the service manual, it might be wise to pay the pros. What you are experiencing is not a run of the mill problem.

Salim

 

Fuse #32; referred to as HEATER, a 15 Amp fuse, is top on the third of four rows of the fuse box behind the drop out change container, to the left of the steering column. Use the white removal tool under the fuse box cover, box under the hood.

Note the section in the owners manual for service procedures for additional information on fuse tool use or fuse locations and descriptions.