Mondial HVAC controls

Ben I think what this all means is:

Stop stops the entire system = no temperature, air distribution or fan speed control. The flap for external air is closed. This is the condition with ignition off.

A/C means "aria circolata" = external air flap closed, the system recirculates internal/cabin air.
A/E means "aria esterna" = external air flap is open and feeds outside air into the cabin.
Windshield symbol = external air flap is open, air is distributed to the windshield, dash side vents and side mirror outlets, centre vent is closed.

The footwell vents are manual only.

None of this sets the temperature, which is solely and manually done via the temp pot.
The system will try to keep the set temp by using either the heater or the air conditioner.
It varies the on/off cycle according to the temp difference to achieve, and uses the cabin air temp sensor and the bleed air sensor to know where it is on the process.
That's why you need to give it time (15 mins) to reach the set temp. After 15 mins, if you don't like it, change it a little either way and wait again If you keep adjusting the temp, the system will keep hunting your goal.

None of this controls the fan speed, which is solely and manually done via the fan speed pot.

Also, when the system is not in STOP mode, the fan will always run at minimum speed to prevent evaporator freeze and force air trough the car to prevent CO entering the cabin in case your windows are closed, especially when backing up.

If you try to achieve a low temp on a hot day with the fan at minimum speed, you won't get a good result.
So use your judgement when setting things

 

Q: Where is the 'switch' on a '88 3.2 that can control either the A/C or the heater being operable but not both? You either get 100% A/C or 100% heat.

BTW, I have an extra potentiometer for the round hot / cold control knob if anybody needs one.

 

There is no such switch. The HVAC ecu determines based on your input on the temp pot and the current cabin temp what it needs to do to reach your desired temp. And you don't get 100% all the time - you might get 100% for a period of time at the beginning but then it will start to cycle as the temp gets closed to the target.
Anyway - the AC is only on/off by nature, and the heater in our cars is on/off too, so it can be controlled by the same logic of 100% on with various lengths of 100% off.

 

PM sent

 

Not quite - in case you set the current cabin temp you will only get air flow, as there is no need for a temp change.

 

Of the only two items on my car I need any attention to (as the car just came off a full restoration) is a slight oil seep at the pan and the AC is set to either heat or cold. Now for obvious reasons here in Phoenix its set to cold AC. As a side note, this systems just about blows ice cubes with a strong fan, quite impressive. What a far cry from my last two 308's!

 

I think it might just be 100% AC because it can't reach the set temperature with your current ambient air temp?
It's the same in HK during daytime; the AC runs permanently. But at night, with just a couple of degrees lower outside air temp but no solar load, the AC starts to cycle after an initial burst of a few minutes of cold air.

 

Thanks for posting, this it is very interesting. It all makes sense, except for all the warning with the "stop" button.

Why shouldn't it be pressed when the car is started--it seems that if the system is off it shouldn't matter.

I can't figure out why turning the A/C off when it is running would be a problem either, since that is basically what the thermostat does, expect for maybe shutting the fan off as well when it is cold and creating an ice chunk? Anyone have any ideas?

 

When I went to pick up my car from my recent major service in fort Lauderdale after a test drive with Tim Stanford, it was early in the morning and we decided to try the air conditioning, because he had installed a new AC compressor dryer and recharged the system with r12, the first blast of air that came out of the vents was hot, Tim immediately told me that I had a leak in my heater valve, as an expedient, since the service was done and I was about to load the car up to come home to Central Florida, he told me to install a ball valve in the heater circuit as depicted in the pics below, before installation of this valve I was getting 49° air out of the center vents. Afterwards I was getting 42° air, yeah I know I should have just replaced the valve but it's hard to get to and this is an expedient that works in Florida because I never use the heat, so some things to think about if you want to get an optimal performance out of the air conditioning. I closed off the footwell vents, the dash vents, and the vents going to the side window so everything comes out of the center vents, which it kind always did anyway, pics below.
Alden

 

Can anyone speak to this? I have the same question.


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Those warnings were US only; nothing is mentioned in the European version of the QV.
Ice building is the only reason I could sort of see but there is a temp sensors on the evaporator to cut the compressor in that case too, plus the max pressure cut-out at the dryer so it seems to be an overkill. The system is protected. I have been using the HVAC without knowing about these warnings ever since I own the car and have not experienced any issues I could attribute to any of these red warnings. A US product liability protection measure for F?

 

I have a Cab and whenever the hood is down, the AC unit is pushed to OFF in order not to have the resistance of the AC compressor on the crank.
Works perfectly for hours of driving like this. And this is a US-delivered car.

On the other end: What is also not recommended, to run the AC on very hot outside air (therefore the settings A/E and A/C). However we kind of melted in a traffic jam in Kroatia last summer, so we had the AC on full blast whilst enjoying the sun from above. Again, the system delivered without failure and engine did not get hot either.

Just a perfect summer vehicle...........

Me too though would prefer to have A/E not running the compressor for above mentioned resistance. In northern Europe you have plenty of days that outside air provides more than enough cooling.... especially this "summer" : (

 

You do this manually?

That's what it is for! I especially use it when it's hot!!!

Yes - I was thinking of modifying the circuit to allow that.

 

The picture of the quarter-turn ball valve is exactly what I’ve been seeking. 1. If that little knurled knob is a bleed - that is brilliant! 2. Please provide info regarding where Ivan obtain that specific valve.

I live in Southern Calif., so my situation is similar to folks in Florida, Texas, etc. We rarely need the heater system on at all. The complicating factor is the htr flap valve is energized always open unless countermanded electronically. Over years this “flap” gets stuck in the open position or the electronic signal to close stops working. Regardless, these 40 year-old cars don’t like being opened up - other things get broken - AND my heater is almost never used.

I’m trying to give FChatters a rough idea of why I need the valve. The bleeder is very necessary because the radiator is miles away from the engine and the coolant system is just about the most important system in the car.

Thanks Alden,

SG


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That is is a bleeder on the bottom of the valve and I got it at the local Ace hardware! A 3/4" valve fit inside the hose perfectly.
Alden

 

I think I'm going to make this mod a separate post, it's too good to get buried in a discussion of electrical controls, and the bleeder valve is a very high point in the cooling system, higher than the radiator bleed, what do you guys think?
Alden

 

When you found a simple fix for that, please let me know.

Greetz,
Mondi Cab

 

Many thanks! This is an extremely important fix for our older cars in warm locales. I’ve been reading about types of valves. The ball inside should be brass or other durable metal. Some valves have a plastic ball. Be careful. Also, make sure proper air bleeding is done after adding the valve. SG


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Nice! Let us know how you progressed.

 

I want to better understand the heater. Some folks say they can hear a noise when the the (nearly archaic) climate control system responds to a [Htr]/AE/AC or Stop button push. … or when the ignition key is turned to first on position.

1. Is there an air flow flap noise, or is it a heater water flow valve.

2. Some folks say the heater water flow valve is wired to be open (12v charge) almost always - except when AC or climate control sensor cuts it. [ My car - climate sensor and AC are removed which my be source of my problem].

3. Can a certain wire be disconnected at fuse box to halt whatever is allowing heater to be hot constantly?

Alden’s fix is looking pretty good, but an electric disconnect might be an option too.

I think many FChatters have heater hot issues given existing comments from Mondial and 308 owners.

41 year-old car! SG


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The air flaps are vacuum controlled.
The heater valve and compressor clutch are electrically controlled.

Without the engine running and producing a vacuum, the flaps won't move. And the outside air flap is closed. This prevents insects from entering the system when the car is parked. So switching the ignition on doesn't move the flaps.

To have a switching noise from the heater valve when the ignition is turned on, AE, AC or DEF must be pressed, and the selected temp must be higher than the ambient temp.

This is incorrect on several levels. The heater valve is open when no power is applied to it. This allows coolant change and system bleeding without powering up the electrical system.
Neither the AC nor the climate control sensor cuts the heater. The HVAC ecu controls the use of the either the AC or the heater, or neither. The decision is based on the difference between the temp set on the control and the measured temp of the cabin air.

No. You'd have to put 12V to the heater valve while the ignition is on to close it. Or you can bypass it with a short tube linking the inlet hose from the sill to the outlet hose going through the firewall.

No, it would have to be an electrical connect.

The 308's system is entirely different from the Mondial's, so those "solutions" won't work for it.

 

WOW. Thanks. Will read the above slowly later today.

Just had a thought: since my interior climate sensor is gone what happens if a jumper is added there?


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The cabin air temp sensor reads a resistance between approx. 35 kΩ at 0°C and 5 kΩ at 40°C.
Shorting it would probably in the best case confuse the ecu and in the worst case damage it.
I would rather add a 5 kΩ resistor to tell the ecu it's 40°C in the cabin so the heater doesn't kick in.

 

I think in Southern California the “add a 5k Ohm resistor” is the simplest technique to try. That will be my first approach. Thank you.


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