Does Residual Heat Function work?

**mgm** · 11-06-2009 10:16 AM

Has anyone gotten this feature to work? I tried and doesn't seem to do anything. A friend of mine told me about that feature in his BMW and told him the Audi has it too,lol. This is what the manual says:

"You can press the OFF button when the ignition is switched off to
activate the "residual heat" function. The system will then heat the

interior using the remaining heat in the engine coolant."

**B_Boy** · 11-06-2009 10:47 AM

what really? never heard of this

**beemercer** · 11-06-2009 11:13 AM

Not related, but I saw residual heat and started thinking of applied chemical engineering thermodynamics... glad it's something different

**myb5quattro** · 11-06-2009 11:16 AM

I've never heard of this either, but it sounds interesting

**sakimano** · 11-06-2009 11:37 AM

My Mercedes had this. It was great in the winter.

If you're gone under 5 minutes, the car will still be warm even without the feature so it's not noticeable.

If you're gone 40+ mins, the car will be cold even if you use this feature.

It's best for 5-40 minutes...before and after you won't notice it.

**akaisuzu** · 11-06-2009 11:38 AM

Originally Posted by sakimano

My Mercedes had this. It was great in the winter.

If you're gone under 5 minutes, the car will still be warm even without the feature so it's not noticeable.

If you're gone 40+ hrs, the car will be cold even if you use this feature.

It's best for 5-40 minutes...before and after you won't notice it.

Winter coffee break!!!

**beemercer** · 11-06-2009 11:45 AM

Not related, but I saw residual heat and started thinking of applied chemical engineering thermodynamics... glad it's something different

**Jacon** · 11-06-2009 11:47 AM

Originally Posted by beemercer

Not related, but I saw residual heat and started thinking of applied chemical engineering thermodynamics... glad it's something different

thank god I wasn't the only one

**John4378** · 11-06-2009 11:57 AM

Us engineers hear "residual heat" and immediately start thinking thermo. I think it's in our DNA, lol.

As a mechanical engineer in the oil & gas business I start thinking about plant equipment such as compressors that have heat reclamation systems on them to appease the environmentalists

. The heat saved & re-used doesn't save that much in operational capital.

**dieatomic** · 11-06-2009 12:23 PM

HA HA im in the pharmaceutical business in the bronx and when we hear residual heat we think of a grudge that an insurance company might have toward our pharmacy

**mgm** · 11-09-2009 08:38 AM

So has anyone been able to activate it yet? Still can't on mine :(

**myth7676** · 11-09-2009 09:51 AM

Originally Posted by mgm

So has anyone been able to activate it yet? Still can't on mine :(

no. i dont such a feature exists on the A4

**DavidB8** · 03-25-2010 12:50 PM

I thought this was a feature that was only active if you had the Auxiliary heater. It's the only device that can be powered on its own and flow the coolant without any outside engine source.

Thats pretty well the reason I didn't pursue this one any further.

Anyone here have this function? I now the Auxiliary heater isn't available to the UK and North America so it maybe a bit of a trick if it related. And just some coding if not :)

**snelldogg** · 03-25-2010 01:08 PM

My 335 had it. Worked great. Good feature Audi should adopt.

**DavidB8** · 03-25-2010 01:13 PM

Just found this:

You can press the button when the ignition is switched off to
activate the "residual heat" function. The system will then heat the
interior using the remaining heat in the engine coolant.

Applies to vehicles: with deluxe automatic air conditioner plus

Its that last part that catches me.. I wonder what constitues air conditioner plus.

**mgm** · 03-25-2010 01:17 PM

That is what the tri-zone a/c system is called (with rear ducts). So we should have it, but can't tell if its working or not. Maybe it does circulate coolant but fan doesn't operate.

**DavidB8** · 03-25-2010 01:57 PM

have a working theory. Will try it when i get home. Have to warm the car up and then try a couple of things. So 3-4 hours maybe? And I'll report back.

**Für Deutschland** · 03-25-2010 05:19 PM

i almost got a b7a4 and the salesman told me about this feature, no idea how to work it though

**Alkivar** · 03-25-2010 06:24 PM

I thought I read somewhere this feature was only available on the diesel cars?

**DavidB8** · 03-25-2010 06:51 PM

No not just diesels, deisels have auxillery heaters that can pump more heat into the car while it's still warming up. Different system.

I was doing some reading on a VW forum and and a bunch of them were talking about the same thing.. Only difference is they actually got the option on the MMI. For them to activate it they said you have to have the car up to operating temperature, engine not running but car still powered up then activate on their MMI. I tried the exact same procedure but using the off button and got nothing. I tried every bit in the byte on the HVAC module and couldn't get anything to go except the menu for supplementary heater which did nothing but throw DCTs.

Now I just had a look in my manual and I can't seem to find anything on residual heat. .Maybe I'm missing it. I know in the past I've always been looking at the electronic version which is not for North American cars.

Unless we can get some more insight from someone with this working not sure how to proceed. If I was near a dealer and could find it in our manual I would go to the dealer and ask them.

**mmurph318** · 03-25-2010 07:00 PM

I have it on my Touareg. Their is a separate button marked " REST" on the climate control unit. For the VW, I am pretty sure I press it first and then turn the car off. I didn't recall seeing the feature when I read over the B8 manual. I will check again.

**DavidB8** · 03-25-2010 07:07 PM

Originally Posted by mmurph318

I have it on my Touareg. Their is a separate button marked " REST" on the climate control unit. For the VW, I am pretty sure I press it first and then turn the car off. I didn't recall seeing the feature when I read over the B8 manual. I will check again.

So what happens when it turns on? Do you hear anything or feel anything from the vents?

**mmurph318** · 03-25-2010 07:26 PM

Originally Posted by DavidB8

So what happens when it turns on? Do you hear anything or feel anything from the vents?

The pretty light on the button comes on and the fan comes on at what appears to be the lowest setting (ie it is barely audible and you can feel it coming out of the footwell vents only). I think it automatically turns off after 20-30 minutes. I can't figure out Audi/VW. My B6 Avant had rear seat heating, under-seat trays, folding mirrors, full size spare. Now, even with the prestige pkg., these things are absent. The V6 TREG has folding mirrors, residual heat, footwell lighting, lights under the side view mirror. I guess I need to get a VAG COM/extra parts to enable some of these on the B8. Don't get me wrong..... I love the improvement on the B8.

**mgm** · 03-26-2010 05:12 AM

Originally Posted by DavidB8

Now I just had a look in my manual and I can't seem to find anything on residual heat. .Maybe I'm missing it. I know in the past I've always been looking at the electronic version which is not for North American cars.

Interesting, I wonder if they left it in the manual by mistake in the '09s for NA and made the correction in '10s. More NA decontenting :(

**DavidB8** · 03-26-2010 06:41 AM

Who knows... I rechecked my manual against the UK and if it's in the manual it's not in same spot. I can try and compare coding to see if it's some thing like that but. I tried coding the controller and tried turning on some of the adaptations and nothing. There were a bunch that required security codes and there isn't one listed.

Back burner for now I think. Sorry, I tried.