What does 'reheat' button on aircon do?

[BTB 500]

As above, the aircon on our Vito has a 'reheat' button (4, on the diagram below):

The manual just says

Reheat function (dehumidification)
The reheat function quickly demists the windows and dehumidifies the air inside the vehicle.

Any idea what actually happens when this function is switched on?

Full climate control (which our vehicle doesn't have) has the same button

Reheat function (dehumidification)
The vehicle is equipped with a reheat function, which ensures that the windows are rapidly demisted and that the air in the interior is dehumidified.

In both cases the manual says to switch this on if the windows are misted up. I thought dehumidification was a standard part of climate control, if not aircon?

 

[seymansey]

From your description, it looks like it performs the same function as whats on my W202's climate, the front screen demist function - maximum temperature is set and aircon is turned on, and my temp display says 'HI'

 

[andy_k]

does it switch the dryer on?

 

[BTB 500]

does it switch the dryer on?

That's what I'm guessing, but I thought climate control (if not aircon) managed humidity all the time anyway?

The 'screen heating button' on the climate control also activates this 'reheat' function. The manual says when that button is pressed

The automatic climate control automatically switches to the following settings:

• Maximum blower output and temperature increase
• Air to the windscreen and front side windows
• Economy mode deactivated
• Reheat function (dehumidification)

 

[Giantvanman]

Apologies for resurrecting old thread

I thought I would share a complete moment………

Having deliberately and in true obstinate fashion, been trying on and off to work out WTF the Reheat Function was all about by using the owner's manual provided. :fail

So I gave up, used internet, found this thread and this online manual:-
Online Owner's Manual [vito]

and found it is to do with dehumidification.
IF I have understood correctly, it is a single button operation to remove humidity whilst in air conditioning mode. It can only be used for short periods.

Does this mean it provides extra dehumidification with air-con or does air-con not have dehumidification?

No guessing how stupid I feel.

------

 

[Ted]

Edited out stupid reply as I hadn't read through the thread.

 

[IanMSpencer]

Not entirely sure but dehumidification is a natural effect of cooling the air, cold air cannot contain as much water, and in part this is why air con systems normally don't work below about 4c as it doesn't actually do anything, there is no water to dehumidify.

Basically you chill the air and then pass it through the heater to get warm dry air, in summer it'll just cool, but in spring and autumn you'll want warm air added.

The reheat, I am guessing, is an electric heater element to warm the air on start up, or at least is a bonus heating device so although you are cooling the air, it makes sure it seems warm, dry, air onto the windscreen, both to warm the screen so water doesn't condense on it and also the warm air can absorb the water from the screen. If it is a heater coil, then like a rear screen demister you try to put it off asap as it drains the battery. Merc put a timer on the rear screen for that reason.

Keep the air con on all the time and you'll rarely have problems with excessive misting.

 

[BTB 500]

I also think it's an electrical heater of some sort - shame the manual doesn't actually say this!

Keep the air con on all the time and you'll rarely have problems with excessive misting.

We do, but six wet Border Collies in winter can definitely cause heavy condensation on the windows

 

[BIG UN]

I can tell you 100% there is an electric heating element, well there is on 639 Vito's & Viano's anyway cause I've just taken mine out & the power cable had seized on. The only way the cable could be removed was to smash the electric element to bits.

 

[rorf]

It is a very narrow tube coolant pipe

 

[Giantvanman]

Thanks to IanSpencer, BTB500, BIG UN and Rorf.

 

[sherco450]

no button on my 120, 2010 l had previously owned 3, 638 vito,s all with a (rest button) that keeps the cabin warm. l believe only with the heat remaining in the engine bay not an element.

 

[zenman63]

As above it starts the pump and circulates the water around the engine cooling / heating, you cannot change the fan speed or any controls and only works with the ignition off or the key out, if the battery is low it stops running.
The other button just overrides any settings and dehumidifies that bit more than the air con, the other button should close the windows and roof if fitted and re circulate the cabin air, if you had the windows open and press it again they should return open to the same position.

 

[zenman63]

no button on my 120, 2010 l had previously owned 3, 638 vito,s all with a (rest button) that keeps the cabin warm. l believe only with the heat remaining in the engine bay not an element.

We have an electric element in the uk spec heaters, it has huge wires like fitted to the battery and heats up to assist in warm up, like bigun say we have found it in rebuilding his dash and retro fitting air con in his.

Just a quick note, you can easy swap your heater controls for the far superior HH4 air con, we have done 3 now with no problems, my 120 was the first ever to be done and took hours of research before i started.
The harness is now available from MB parts.

 

[Giantvanman]

We have an electric element in the uk spec heaters, it has huge wires like fitted to the battery and heats up to assist in warm up, like bigun say we have found it in rebuilding his dash and retro fitting air con in his.

Just a quick note, you can easy swap your heater controls for the far superior HH4 air con, we have done 3 now with no problems, my 120 was the first ever to be done and took hours of research before i started.
The harness is now available from MB parts.

Is the HH4 the LCD screen climate control system?

If so, I would be interested in the retrofit.

 

[sparkydude]

Yes it is the LCD screen heater control panel mate.

Zenman had a complete retrofit set available a while back, but if he has sold that one will no doubt be able to source another set for you , and will even help with or actually fit it for you i am sure. We did mine as a 95/5 joint effort from his part LoL


Nick

 

[zenman63]

I have another used in the pipe line just let me know.

 

[Giantvanman]

I have another used in the pipe line just let me know.

Just pm'd you. Thanks.

 

[Giantvanman]

BIG shout out

Many thanks to Zenman63 for his advice etc via email.

 

[BIG UN]

Zenman, ssssh your giving the game away before I've done my post!! Lol