Air conditioner temperature control problem

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.

V

Vampo

10 Year
Joined
May 10, 2011
Threads
14
Messages
59
Hi everyone,

I have a LC 2005 Cygnus (more or less the same as the LX470 but RHD)
I recently had to remove (by pass) the coolant lines to my cabin heater radiator as it started leaking coolant into the cabin.

After this bypass, I noticed my Air conditioner temperature control was not controlling the temperature. Basically even if I have the temperature set to very high, its cooling the cabin like its on max cool.

After a few minutes of driving in traffic, I get a nasty burning smell (I initially posted this problem earlier and I was advised to look into the blower motor, which I did, and its fine). The weird thing is, when I know off the AC by pressing the AC button (yet have the blower working), in a about 1 minute the burning smell significantly reduces.

I'm just hacking by brain trying to find the problem

1). Is it that the heater radiator actually controls the AC cooling temperature as well ?

2). did some other plug, sensor, thermostat get pulled out, and as a result the compressor is running continuously.

3). If the compressor operates continuously without switching off, what will happen? can it produce this burning smell in the AC system

4). AC technician who looked at my vehicle very briefly said my High pressure in very very high. much higher than its suppose to be.

5). Any other reasons for the continuous cooling (with no response to the temperature control) and the burning smell

Any help of suggesting is really appreciated.

Thanks.
 
Why didn't the AC technician have a look at to why you have high pressure. You have a sensor under the steering wheel to measure cabin temp, see if that is unplugged, there is a hose attached to the sensor. Check you have nothing blocking your condenser and restricting air flow. Can you regulate the temp on manual not auto.
 
Yes the heater helps regulate the a/c temp, it adds heat to warm the incoming air, without added heat you are going to get 100% full cold a/c.
Without added heat from the heater your a/c is going to turn your truck into a refrigerator. The compressor on your refrigerator runs until the prop temp is reached, then it shuts off, then it comes back on. Your a/c compressor does the same thing b it with no heat it cannot regulate the temp.
Fix your heater.
The compressor can run continuously and not be hurt in the short term, it will shorten it's overall life, meaning instead of lasting 200,000 miles it will last 150,000 miles.
 
I hardly see a leaking heater core in a toyota. It could be water coming down the sunroof drain channels.
How is your coolant level? Do you have to add it often on the days you had the heater hose attached to the heater core?
Also if you directly connect the heater hoses (by-pass), you are simply letting the hot coolant back into the engine block, which is a BAD for the engine. Try to attach a ball vale or something between the two heater hoses (use metal ball valve)
 
nissanh said:
I hardly see a leaking heater core in a toyota. It could be water coming down the sunroof drain channels.
How is your coolant level? Do you have to add it often on the days you had the heater hose attached to the heater core?
Also if you directly connect the heater hoses (by-pass), you are simply letting the hot coolant back into the engine block, which is a BAD for the engine. Try to attach a ball vale or something between the two heater hoses (use metal ball valve)
Click to expand...

How is thatbad for the engine? Letting the coolant that would normally go into the heater back in I mean.
 
It is not that bad, but could lead to heating issues.

When the heater is off, no coolant runs from the hot line in the heater core to cool line in the coolant system so ALL the hot coolant goes through the radiator, cools down and reenters the engine. But when you bypass the heater lines WITHOUT preventing the flow, some of the hot coolant runs directly into the cooler coolant intake and cycles inside the engine. This is what can lead to heating issues.

Older models (without the climate control) have a valve located by the firewall and you can simply bypass because the valve will prevent the flow.
 
Could it be a matter of "burping" the coolant system? Air bubble not allowing proper flow...
 
nissanh said:
It is not that bad, but could lead to heating issues.

When the heater is off, no coolant runs from the hot line in the heater core to cool line in the coolant system so ALL the hot coolant goes through the radiator, cools down and reenters the engine. But when you bypass the heater lines WITHOUT preventing the flow, some of the hot coolant runs directly into the cooler coolant intake and cycles inside the engine. This is what can lead to heating issues.

Older models (without the climate control) have a valve located by the firewall and you can simply bypass because the valve will prevent the flow.
Click to expand...

"Dumping" hot coolant that was supposed to go to the heater back into the mix will not hurt anything. It Will not cause overheating issues, it will not hurt anything.
 
How I would presume it to work is if the heater is set all the way to hot, then the air should be coming from the heater core and the compressor should shut down, the blender door should turn to get the warm air in, I know this will not happen due to the bypass, but the car doesn't know this is bypassed and will try anyway. Depending on the external temps and internal temps the car would operate the blend door and compressor to keep the temp required. Due to the heater being bypassed it would never get hot so should just keep trying, why it would put the compressor on overdrive is a bit baffling if it cannot get heat into the cabin, or why the blend door would be directing air from the evaporator. Just seems a little strange to me, but I don't have first hand experience with this specific system so I might be wrong.
 
Hi everybody,

Just an update on this thread. I replaced my radiator and cabin heater core. both were leaking due to a coolant problem. I attached a few pics.

The temperature controlling problem got sorted once I replace the heater core. I guess its connected in someway to controlling the temperature in climate control systems.

The weird smell also disappeared. I guess that was the coolant.

However I still get the burning smell from the vents. smells like a circuit board burning. To be a bit more specific

- The smell comes only after starting the vehicle in the morning and getting into traffic. about 20min into traffic
- smell is not there in short trips and as long as the vehicle is moving at 25mph +
- The smell doesnt come on cooler / rainy days (i'm assuming it has something to do with the ambient temperature)
- The smell goes off if I switch off the air conditioner (compressor) but while having the blower fan working

20170915_183941.webp
20170915_184158-2.webp
 
Have you tried a anti bacterial cleaner for your A/C? This can give off some bad smells if bacteria and crude has built up, not sure about LHD version but you can open the door where the pollen filter is supposed to be and give the evaporator a good clean, also do you have a pollen filter fitted, mine doesn't I have a door but I cannot get a filter to fit, rubbish design by Toyota on this I think.
 
Vampo said:
Hi everybody,

Just an update on this thread. I replaced my radiator and cabin heater core. both were leaking due to a coolant problem. I attached a few pics.

The temperature controlling problem got sorted once I replace the heater core. I guess its connected in someway to controlling the temperature in climate control systems.

The weird smell also disappeared. I guess that was the coolant.

However I still get the burning smell from the vents. smells like a circuit board burning. To be a bit more specific

- The smell comes only after starting the vehicle in the morning and getting into traffic. about 20min into traffic
- smell is not there in short trips and as long as the vehicle is moving at 25mph +
- The smell doesnt come on cooler / rainy days (i'm assuming it has something to do with the ambient temperature)
- The smell goes off if I switch off the air conditioner (compressor) but while having the blower fan working

View attachment 1551105 View attachment 1551106
Click to expand...


Thank you for updating.

The smell will go away eventually on it's own. If you want it gone sooner you will need to clean the HVAC system, as mentioned there is special cleaner you can use to kill bacteria and alge. The leaking coolant that collected is what is causing your smell. Once it is gone, the smell will also be gone.

Who replaced your heater core? How much was it? If you did it how long did it take you?
The radiator? Same questions.
 
Spike555 said:
Thank you for updating.

The smell will go away eventually on it's own. If you want it gone sooner you will need to clean the HVAC system, as mentioned there is special cleaner you can use to kill bacteria and alge. The leaking coolant that collected is what is causing your smell. Once it is gone, the smell will also be gone.

Who replaced your heater core? How much was it? If you did it how long did it take you?
The radiator? Same questions.
Click to expand...


Hi,

I got my heater core and radiator replaced by my local workshop. They did a great job. The total cost for was taken by the coolant manufacturer. I believe it was about $1300 for the spares and labor. It took like 3 days are the entire dashboard had to be removed. Basically everything was removed. The Radiator took about 1 day. hope info helps.

BTW my burnt smell air conditioner is still the same. if I put the temperature to 28 degrees C. it does off. Also if I switch the compressor off it goes away. still trying to figure it out.
 
You must log in or register to reply here.

Share this page

Back
Top Bottom