Automatic Temperature Control
#11
11-24-2008, 10:18 AM
Re: Automatic Temperature Control
"Why does the AC always turn on...."
Because some idiot(s) at NipponDenso in Japan, or the US counterpart, Denso US, thought it would be a good idea to run the A/C during the wintertime to help in dehumidifying the incoming airflow and thereby prevent windshield fogging.
For many years I simply disconnected or somehow disabled the A/C compressor during the winter months. Some newer Denso designed systems have the ability, dealer only parameter set, to allow you to disable the A/C indefinitely.
Running the A/C for dehumidification is a total wild card, functionality depending strictly on the welms of mother nature, and we all know just how fickle she might be. Additionally there are HAZARDS associated with this, also dependent of mother nature.
Experienced episodes of sudden windshield fogging...??
Because some idiot(s) at NipponDenso in Japan, or the US counterpart, Denso US, thought it would be a good idea to run the A/C during the wintertime to help in dehumidifying the incoming airflow and thereby prevent windshield fogging.
For many years I simply disconnected or somehow disabled the A/C compressor during the winter months. Some newer Denso designed systems have the ability, dealer only parameter set, to allow you to disable the A/C indefinitely.
Running the A/C for dehumidification is a total wild card, functionality depending strictly on the welms of mother nature, and we all know just how fickle she might be. Additionally there are HAZARDS associated with this, also dependent of mother nature.
Experienced episodes of sudden windshield fogging...??
I used to think it was kind of silly to run the A/C in winter, but I've changed my mind on this. Anyone that has the regular joy of driving during bitterly cold below freezing temps knows that a very risky time is when the car is still cold and you have multiple moisture emitters (ie people) in the car. Then your issue is not fogging but actual inside window icing if you don't maintain a dry airflow from the beginning. And once your window ices its not going to "de-ice" anywhere near as quickly or easily as de-fogging with or without the A/C until the car gets warmer. This can easily catch people off guard because if you drive away with a clear windshield on a freezing sunny day the windshield may actually be a bit warm from the dash radianting some heat, until the cold air starts hitting it from driving and rapidly begins the icing process turning your vis to almost 0 in a few seconds.
It has value, but not to everyone's situation.
Last edited by Droid13; 11-24-2008 at 10:31 AM.
#12
11-24-2008, 11:20 AM
Re: Automatic Temperature Control
This is specific with the TCH, with the ATC on, the AC will not turn on unless the AC button is pushed. It will not cool the cabin air even if you turn the temperature down.
The TCH will not turn on the AC to defog the windshield unless the front windshield defog button is pushed. The rear windshield defog button uses electric heating only.
This gives the most flexibility for the driver to choose to save energy.
This is quite different from US made cars and some foreign cars which will turn on the AC when air flow is selected for windshield only.
The TCH will not turn on the AC to defog the windshield unless the front windshield defog button is pushed. The rear windshield defog button uses electric heating only.
This gives the most flexibility for the driver to choose to save energy.
This is quite different from US made cars and some foreign cars which will turn on the AC when air flow is selected for windshield only.
"Why does the AC always turn on...."
Because some idiot(s) at NipponDenso in Japan, or the US counterpart, Denso US, thought it would be a good idea to run the A/C during the wintertime to help in dehumidifying the incoming airflow and thereby prevent windshield fogging.
For many years I simply disconnected or somehow disabled the A/C compressor during the winter months. Some newer Denso designed systems have the ability, dealer only parameter set, to allow you to disable the A/C indefinitely.
Running the A/C for dehumidification is a total wild card, functionality depending strictly on the welms of mother nature, and we all know just how fickle she might be. Additionally there are HAZARDS associated with this, also dependent of mother nature.
Experienced episodes of sudden windshield fogging...??
Because some idiot(s) at NipponDenso in Japan, or the US counterpart, Denso US, thought it would be a good idea to run the A/C during the wintertime to help in dehumidifying the incoming airflow and thereby prevent windshield fogging.
For many years I simply disconnected or somehow disabled the A/C compressor during the winter months. Some newer Denso designed systems have the ability, dealer only parameter set, to allow you to disable the A/C indefinitely.
Running the A/C for dehumidification is a total wild card, functionality depending strictly on the welms of mother nature, and we all know just how fickle she might be. Additionally there are HAZARDS associated with this, also dependent of mother nature.
Experienced episodes of sudden windshield fogging...??
#13
11-24-2008, 08:53 PM
Ridiculously Active Enthusiast
Join Date: Sep 2006
Location: Beautiful Pacific NW
Posts: 1,678
Re: Automatic Temperature Control
The AC Auto "On" is a customizable parameter, it can be changed to "Manual" by the dealer. The front defogger can also be customized as to whether or not to engage the AC if the AC is off at the time.
I used to think it was kind of silly to run the A/C in winter, but I've changed my mind on this. Anyone that has the regular joy of driving during bitterly cold below freezing temps knows that a very risky time is when the car is still cold and you have multiple moisture emitters (ie people) in the car. Then your issue is not fogging but actual inside window icing if you don't maintain a dry airflow from the beginning. And once your window ices its not going to "de-ice" anywhere near as quickly or easily as de-fogging with or without the A/C until the car gets warmer. This can easily catch people off guard because if you drive away with a clear windshield on a freezing sunny day the windshield may actually be a bit warm from the dash radianting some heat, until the cold air starts hitting it from driving and rapidly begins the icing process turning your vis to almost 0 in a few seconds.
It has value, but not to everyone's situation.
I used to think it was kind of silly to run the A/C in winter, but I've changed my mind on this. Anyone that has the regular joy of driving during bitterly cold below freezing temps knows that a very risky time is when the car is still cold and you have multiple moisture emitters (ie people) in the car. Then your issue is not fogging but actual inside window icing if you don't maintain a dry airflow from the beginning. And once your window ices its not going to "de-ice" anywhere near as quickly or easily as de-fogging with or without the A/C until the car gets warmer. This can easily catch people off guard because if you drive away with a clear windshield on a freezing sunny day the windshield may actually be a bit warm from the dash radianting some heat, until the cold air starts hitting it from driving and rapidly begins the icing process turning your vis to almost 0 in a few seconds.
It has value, but not to everyone's situation.
As a general rule COLD wintertime air is DRY..!!
Last edited by wwest; 11-24-2008 at 09:07 PM.
#14
11-24-2008, 09:16 PM
Ridiculously Active Enthusiast
Join Date: Sep 2006
Location: Beautiful Pacific NW
Posts: 1,678
Re: Automatic Temperature Control
The AC Auto "On" is a customizable parameter, it can be changed to "Manual" by the dealer. The front defogger can also be customized as to whether or not to engage the AC if the AC is off at the time.
I used to think it was kind of silly to run the A/C in winter, but I've changed my mind on this. Anyone that has the regular joy of driving during bitterly cold below freezing temps knows that a very risky time is when the car is still cold and you have multiple moisture emitters (ie people) in the car. Then your issue is not fogging but actual inside window icing if you don't maintain a dry airflow from the beginning. And once your window ices its not going to "de-ice" anywhere near as quickly or easily as de-fogging with or without the A/C until the car gets warmer.
This can easily catch people off guard because if you drive away with a clear windshield on a freezing sunny day the windshield may actually be a bit warm from the dash radianting some heat, until the cold air starts hitting it from driving and rapidly begins the icing process turning your vis to almost 0 in a few seconds.
It has value, but not to everyone's situation.
I used to think it was kind of silly to run the A/C in winter, but I've changed my mind on this. Anyone that has the regular joy of driving during bitterly cold below freezing temps knows that a very risky time is when the car is still cold and you have multiple moisture emitters (ie people) in the car. Then your issue is not fogging but actual inside window icing if you don't maintain a dry airflow from the beginning. And once your window ices its not going to "de-ice" anywhere near as quickly or easily as de-fogging with or without the A/C until the car gets warmer.
This can easily catch people off guard because if you drive away with a clear windshield on a freezing sunny day the windshield may actually be a bit warm from the dash radianting some heat, until the cold air starts hitting it from driving and rapidly begins the icing process turning your vis to almost 0 in a few seconds.
It has value, but not to everyone's situation.
Methinks you have encountered an instance of sudden windshield fogging as a result of inadvertent A/C shutdown. If you happen to drive from a sunny warm area into an area of freezing cold the A/C will have been working and then will shut down automatically as the OAT declines to/toward freezing.
The windshield will have been CHILLED, the A/C evaporator thoroughly coated with condensed moisture, when the A/C shuts down the COLD and DRY incoming airflow will ABSORB the condensate and deposit it downstream on the COLD interior windshield surface.
More like...
BLAM, you have no forward visibility....
Even worse if you happened to have encountered a blinding snowstorm.
Even worse yet is that Denso does not believe in substituting HEAT for the loss of the A/C for dehumidifying the incoming airflow to prevent and/or remove windshield fogging so now you must not only switch to defrost/defog/demist mode but additionally, QUICKLY, manually raise the heating level and blower speed.
Last edited by wwest; 11-24-2008 at 09:21 PM.
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