Add an ON/OFF Switch for rear heater unit? (1 Viewer)

[cumminsBase]

I rarely use the rear a/c unit, yet when I do it is for the cooling, not heating.

The way the system works, when the rear a/c unit is turned on, it opens a valve (?? I haven't checked the service manual). This open valve allows hot coolant to flow through underneath the driver's seat. And then my butt gets all warm.

I thought of adding a nice switch on the dash that would disable the opening/closing of that valve.

Anybody has done this?
What are your thoughts on this modification?

Thanks and Merry Christmas!!!

 

[planomateo]

Seems to me you're over-complicating this. Use of the auto, temp setting switch along with turning off the rear when you don't need it should meet your needs.

 

[badlander]

I thought that there were no valves in the cooling/heating system. From the info I have seen it is constant free flowing.
Someone please correct me if I am wrong.....

 

[Trunk Monkey]

If the rear hvac is on and the rear controls are set to cold, you shouldn't have any heat on the lower portion.

 

[uHu]

The rear AC and the rear heater are two independent, separate systems. The rear AC is for cooling only and has it's own switch up front (in addition to the controls at the back), shown here just to the right of the red circle:

The rear heater is another system, located under the driver's seat (LHD) and under the central storage box; and is always heating your bum, as you put it. But(t) I've never ever felt any heat from under my seat. It has it's own switch here:

Are you saying that you have both rear AC and rear heater?

 

[oakback]

I only have the button in the first pic, but if the rear controls are switched to hotter temps, it'll blow hot air. Is that different than rear heat?

 

[uHu]

There is no heat added to the air in the rear AC system, it just recirculates the cabin air and cools it down if required.

 

[Dilspec]

Mirroring what others have said I believe the rear is AC only. Heat only comes through floor vents in the back for the most part.

 

[arkmm]

Mirroring what others have said I believe the rear is AC only. Heat only comes through floor vents in the back for the most part.

There’s no rear heat?! I’ve been freaking out for no reason??

 

[Cargo1234]

I experience something similar.
Rear A/C runs , sends out cold air from the rear UPPER vents.
However, it begins to cycle on and off erratically.
Over the course of a long drive it will switch off the upper air and then goes to heat from the lower vents on the backside of the center console.
This sends warm air between the seats (also because of the the s***ty bent up WeatherTech 2nd row matt) and makes the front seats hot AF.
I can usually turn off the Rear A/C button from the front panel and wait a minute or two then kick it back on to the A/C blowing again from above.

I have yet to figure out what is happening. I have thought about replacing the upper A/C temp sensor in the head liner (above 2nd row seats)

I have a 99 LX, Rear A/C control panel above 2nd row. I have tried every conceivable adjustment from both the front and rear control panels.

 

[Mike NXP]

There’s no rear heat?! I’ve been freaking out for no reason??

Yeah as shown in the controls in the rear the cold air only comes through those top vents as it is an independent system wheras the rear heat flows through center console. This also took me a bit to make sense when I was camping and wanted heat to blow out of the top vents.

To the OP If running rear AC maybe you should switch to the head only mode to avoid any airflow through the center

 

[KFunk740]

The rear AC and the rear heater are two independent, separate systems. The rear AC is for cooling only and has it's own switch up front (in addition to the controls at the back), shown here just to the right of the red circle:

The rear heater is another system, located under the driver's seat (LHD) and under the central storage box; and is always heating your bum, as you put it.

So, I found this interesting, and just played with both of them for a while in my '99 LC, and found it to be entirely wrong.

The rear controls on the ceiling most definitely control the rear heat on the floor, and both are turned on by the 'fan rear' button up front.
There was no heat coming from behind the console the entire time I drove to work, until I turned on the 'fan rear' button up front. Then on the rear ceiling controls, if I turned it to cold it shifted toward only cold air coming out up top and no heat from bottom. Turn it toward hot, and cold air up top turns off and floor heat turns on.
I have no idea if there's any valve switching coolant flow off and on, and the controls may just be turning an electric fan on and off that get the heat from it. But I just know the rear console vents were cold as can be until I switched on the rear system.

Now my issue, which is why I was looking at thread like this, is that I often get my right foot roasted while its on the gas pedal. Not sure what thats about, or if turning rear system on or off will affect that. For some reason too, whenever I set the front center knob on Auto, it always decided to blast air at my feet only, will never go up top or split between the two. Not sure what that's about.

 

[Mike NXP]

So, I found this interesting, and just played with both of them for a while in my '99 LC, and found it to be entirely wrong.

The rear controls on the ceiling most definitely control the rear heat on the floor, and both are turned on by the 'fan rear' button up front.
There was no heat coming from behind the console the entire time I drove to work, until I turned on the 'fan rear' button up front. Then on the rear ceiling controls, if I turned it to cold it shifted toward only cold air coming out up top and no heat from bottom. Turn it toward hot, and cold air up top turns off and floor heat turns on.
I have no idea if there's any valve switching coolant flow off and on, and the controls may just be turning an electric fan on and off that get the heat from it. But I just know the rear console vents were cold as can be until I switched on the rear system.

Now my issue, which is why I was looking at thread like this, is that I often get my right foot roasted while its on the gas pedal. Not sure what thats about, or if turning rear system on or off will affect that. For some reason too, whenever I set the front center knob on Auto, it always decided to blast air at my feet only, will never go up top or split between the two. Not sure what that's about.

Your explanation is accurate. The "rear" switch on our dash board allows the console in the rear on the ceiling to be powered and active. If you want heat it only comes out of the floor in center console and is coming from up in the engine bay. If you want AC you need to be on head mode and it's coming from the rear AC system, flowing from the main ac compressor. If you have head and foot mode on, the middle center console vent will blow air and probably will be hot.

I also have the same effect most of the time when using auto up front, full blast on floor mode.

All of this is normal and shouldn't be thought to hard about.

 

[KFunk740]

The one thing that bothers me a little, is that the rear control panel forgets its settings if I turn it off and back on again with the front panel. The rear panel always kicks on at the low fan setting. It's a minor problem because my kids sit in child seats and have short arms, and my dog has no arms. So, if I want to start blasting them with cold air at some point in a trip, someone may have to go back there and mess with it. I mean its a minor issue though, at least cold air back there is an option, which is better than any other car I've had.

 

[Mike NXP]

The one thing that bothers me a little, is that the rear control panel forgets its settings if I turn it off and back on again with the front panel. The rear panel always kicks on at the low fan setting. It's a minor problem because my kids sit in child seats and have short arms, and my dog has no arms. So, if I want to start blasting them with cold air at some point in a trip, someone may have to go back there and mess with it. I mean its a minor issue though, at least cold air back there is an option, which is better than any other car I've had.

Interesting, my settings hold once switched off and back on...I'm in a 2002.

All winter long I keep it on heat with the rear panel, and click it on from up front when needed. AC in the summer, same concept

 

[KFunk740]

Interesting, my settings hold once switched off and back on...I'm in a 2002.

All winter long I keep it on heat with the rear panel, and click it on from up front when needed. AC in the summer, same concept

Hmmm, maybe I have a problem with a 12V constant wire, or a little dead button battery somewhere. Well there goes a couple hours of weekend time someday.