weird problem during traffic jam yesterday

[HRTROB]

Originally Posted by stugray

I'll try to explain slowly....
Air Conditioners are heat pumps. They pump heat out of your interior into (wait for it) into your radiator (the thing trying to cool your engine).

AC systems take quite a bit of power: both HP from the engine and extra electricity for the fans (more drag on the alternator).

So while sitting in bumper to bumper traffic you are running a car in a way that generates the most heat while providing it the minimum cooling capability.

The system can detect the rising temps in the cooling system, first the car will turn on the electric fans to try to provide extra cooling for the radiator.
It even has more than one speed for those fans.

If that is not enough, it will take further measures and turn off your AC compressor. Why? because it knows that it generates more heat.
So I will rephrase "People who know what is good for their cars will not sit in traffic, not moving, with their air conditioner running"

Coolant temp will be higher in traffic when the AC is off. This is because the fans only turn on when the the coolant temp reaches 100C. Try it yourself, turn off the AC in traffic and watch your coolant temp creep up.

With the AC on in traffic, the fan is always on and will keep coolant temps below 95C.

[wparsons]

If the car was getting hot enough that it turned off the AC to prevent it from overheating you would most definitely notice the temp gauge running way too high.

Plus, it's not THAT hot in Canada yet, so it really shouldn't be having heat issues. I've had days where in BAD traffic the AC isn't as cold as it normally is, but it's still cold. I've never had it turn right off, or had the temps creep up (based on the gauge, not by accurate logging) either.

[J_kennington]

Originally Posted by stugray

I'll try to explain slowly....
Air Conditioners are heat pumps. They pump heat out of your interior into (wait for it) into your radiator (the thing trying to cool your engine).

AC systems take quite a bit of power: both HP from the engine and extra electricity for the fans (more drag on the alternator).

So while sitting in bumper to bumper traffic you are running a car in a way that generates the most heat while providing it the minimum cooling capability.

The system can detect the rising temps in the cooling system, first the car will turn on the electric fans to try to provide extra cooling for the radiator.
It even has more than one speed for those fans.

If that is not enough, it will take further measures and turn off your AC compressor. Why? because it knows that it generates more heat.
So I will rephrase "People who know what is good for their cars will not sit in traffic, not moving, with their air conditioner running"

So, the fact my car has never overheated while not moving with the AC on means what?

Can you explain to me how the AC pushes heat into the radiator, since you know...it's not connected in any way. You almost had one part right though, AC is a setup of heat exchangers, NOT heat pumps. The condenser is what takes the heat, NOT the radiator. It then goes to the evaporator which once again, reduces heat. The ONLY part of the hvac system to deal with the radiator is the, heater.

As for the idle issue, you all do know there is a tsb out for that right?

[Tye300]

If the ac blew warm air while the idle became erratic, that is a clue. It's either the ac system could not handle the heat and the pressure in the ac system shot up. This usually causes the compressor to stop because you cannot add more pressure, thus stopping the freon from circulating.
This scenario usually happens when the coolant temps cannot handle the heat and the cooling system simply overheats. This happens a lot in Manila because of the heat and bad traffic.
Things to check for are:
Radiator coolant level
Radiator cap might be leaking
Radiator fans might not be turning on that's why it happens during traffic
AC system might have sprung a leak and caused a vacuum leak which made the idle erratic

[stugray]

Originally Posted by J_kennington

So, the fact my car has never overheated while not moving with the AC on means what?

It means nothing (at least with regards to my argument)

Originally Posted by J_kennington

Can you explain to me how the AC pushes heat into the radiator, since you know...it's not connected in any way.

The AC radiator and the engine radiator ARE STUCK TOGETHER.

Originally Posted by J_kennington

You almost had one part right though, AC is a setup of heat exchangers, NOT heat pumps. The condenser is what takes the heat, NOT the radiator. It then goes to the evaporator which once again, reduces heat. The ONLY part of the hvac system to deal with the radiator is the, heater.

You apparently never took thermodynamics.
In the refrigeration cycle, a heat pump transfers heat from a lower-tempeature heat source (the evaporator in the passenger compartment) through the compressor (which makes the refrigerant HOT as it is compressed back to liquid) then it dumps that heat into a higher-temperature heat sink (The AC radiator).

The AC radiator IS ATTACHED TO THE ENGINE RADIATOR.
In SOME cars the AC radiator is INSIDE the engine radiator.

By running the AC you are dumping heat directly into the radiator. This is especially hard on the system when there is less air flow through the two radiators than when the car is moving.

When you argue with an engineer you make yourself look stupid.

[Minovsky]

Originally Posted by wparsons

If the car was getting hot enough that it turned off the AC to prevent it from overheating you would most definitely notice the temp gauge running way too high.

Plus, it's not THAT hot in Canada yet, so it really shouldn't be having heat issues. I've had days where in BAD traffic the AC isn't as cold as it normally is, but it's still cold. I've never had it turn right off, or had the temps creep up (based on the gauge, not by accurate logging) either.

that is true it wasnt that hot that day. hmm

[stugray]

Originally Posted by wparsons

If the car was getting hot enough that it turned off the AC to prevent it from overheating you would most definitely notice the temp gauge running way too high.

I'm not suggesting that the engine was running way too hot or about to overheat.

I was just pointing out that the ECU software cycles the AC compressor on and off for various reasons.
One can be for economy - No reason to run the AC at 100% duty cycle if the demand is only 20%. So it turns the AC compressor on and off via the solenoid clutch in the AC compressor.
The software can just decide to give less and less drive to the AC pump as it detects engine temps rise.

I thought I even heard of someone comment that their AC would not work after driving the car at the track hard because the engine temps were too high...

[J_kennington]

Originally Posted by stugray

It means nothing (at least with regards to my argument)



The AC radiator and the engine radiator ARE STUCK TOGETHER.



You apparently never took thermodynamics.
In the refrigeration cycle, a heat pump transfers heat from a lower-tempeature heat source (the evaporator in the passenger compartment) through the compressor (which makes the refrigerant HOT as it is compressed back to liquid) then it dumps that heat into a higher-temperature heat sink (The AC radiator).

The AC radiator IS ATTACHED TO THE ENGINE RADIATOR.
In SOME cars the AC radiator is INSIDE the engine radiator.

By running the AC you are dumping heat directly into the radiator. This is especially hard on the system when there is less air flow through the two radiators than when the car is moving.

When you argue with an engineer you make yourself look stupid.

Tell ya what, I'll just say. "Sure" and leave it at that.

[stugray]

Originally Posted by J_kennington

Tell ya what, I'll just say. "Sure" - running the AC dumps more heat into the engine cooling system than not running it.

Fixed that for you.

[zooki]

Most(if not all) car manafacturers spend a lot of time and money making sure their cars will not overheat on hot days. If you've ever seen pictures of the "heat soak" buildings a lot of them have in Arizona you'll know that they leave their automobiles sitting in them, running, with all the accessories on for hours and hours. I find it really hard to believe Toyota skipped this step in testing. I would have to say its something else, and NOT normal.
As far as arguing with engineers, I've worked in the petrochemical industry for 20+ years, and can assure you engineers CAN and ARE wrong quite a bit. We in the operations side of things just love it when we get brand new engineers at work...it seems that some of them trade in their common sense for that sheepskin to hang on their wall....

[J_kennington]

Originally Posted by zooki

Most(if not all) car manafacturers spend a lot of time and money making sure their cars will not overheat on hot days. If you've ever seen pictures of the "heat soak" buildings a lot of them have in Arizona you'll know that they leave their automobiles sitting in them, running, with all the accessories on for hours and hours. I find it really hard to believe Toyota skipped this step in testing. I would have to say its something else, and NOT normal.
As far as arguing with engineers, I've worked in the petrochemical industry for 20+ years, and can assure you engineers CAN and ARE wrong quite a bit. We in the operations side of things just love it when we get brand new engineers at work...it seems that some of them trade in their common sense for that sheepskin to hang on their wall....

It's cool. Engineers are always correct. Even when they have nothing to do with engineering the system in question. Makes me wonder how every car I've ever owned has never raised a single degree in temp while running the AC.

[Calidrifter]

we are all dumber for reading this nonsense...

[stugray]

Originally Posted by J_kennington

It's cool. Engineers are always correct. Even when they have nothing to do with engineering the system in question.

I made it a point to call you out because you were blatantly wrong in calling ME out about how an air conditioner works.
And note: You never said Oops I am sorry I was wrong.

Originally Posted by J_kennington

Makes me wonder how every car I've ever owned has never raised a single degree in temp while running the AC.

Oh I wasnt aware that you have run instrumented tests on your car in the past....
I can say for a fact: You are wrong. Running the AC DOES make your engine run hotter. Period.
One of the things I do for a living is instrumented thermal testing of systems far more complex than a car. SO even your "Even when they have nothing to do with engineering the system in question." is incorrect.

You said that an air conditioner was not a heat pump, it was a heat exchanger. You were wrong.

And it is 100% a fact that the running the AC adds heat to the engine's cooling system.
You dont need to be an engineer to understand this.

AND I never said that the OPs car was overheating or WAS going to overheat.
I merely stated that as the car sits in traffic with the AC running that the software will begin to do things to keep the car cool.
Such as turning on the electric fans and cycling the AC compressor more frequently.

I honestly have no idea why you even argued with that statement as it is fact.

And being an old fart we were always taught to not run the AC unless the car is moving.
I guess young kids these days think cars have always been perfect and have had computers in them to manage themselves.

Originally Posted by zooki

As far as arguing with engineers, I've worked in the petrochemical industry for 20+ years, and can assure you engineers CAN and ARE wrong quite a bit. We in the operations side of things just love it when we get brand new engineers at work...it seems that some of them trade in their common sense for that sheepskin to hang on their wall....

I agree. Except in this case I was not wrong. I was being lectured about how an air conditioning system works by someone who does not know (apparently).

FACT: Running the AC dumps a huge amount of heat into the car's cooling system.
FACT: Running the AC adds a significant load to the engine.
FACT: The car gets less cooling when not moving.

Now you can debate whether it's bad for the car or not all you want, but the above are facts.
Or are they NOT facts just because I am an engineer and engineers are always wrong?

[zooki]

I didn't say you were always wrong, what I said was car manafacturers spend a lot of time testing for things like this. I guess I took exception to the line "When you argue with an engineer you make yourself look stupid". Kinda condescending, no? I've argued with a few, and I've been right. I've been wrong also, but it's not a given.
There has to be something else wrong with the car otherwise every one of these cars would exhibit this behavior in hot climates. I myself live in south Texas and last summer we had many 100+ degree days and my car never exhibited any of these symptoms.
So is my car the exception, or the OP's?