Ventilation always hot

That looks like an expensive way to do a simple thing. Why does Ferrari have to make things so complicated when they don't have to be?

 

Hmm. That's odd. That pipe it connects to looks a bit small for a heater line. Could this be an add-on for the rear seat? If those are actually the lines to the heater, it might explain why it needs a boost pump to get enough hot water to heat the cabin air.

If it's making noise, and you have heat, I'd guess the pump itself is working. Where you might have an issue is with the control logic, if it's running when the controls are set for cooling. But I'd guess that the main engine water pump would keep some coolent flowing in those lines regardless.

If you can find a spare parts catalog, you need to look for the actual heat exchanger (or exchangers) where the engine coolent heats air. The 308 and 328 have two: one for driver, one for pass. Going into each one is a valve to cut off hot water. On the 308, it's cable driven; on the 328, it's electrically controlled.

Do you only have the one heater temperature control for the whole cabin, or do you have different "zones"? There may be additional valves elsewhere in the system.

Oh, and try it when the engine is cold. If you're still getting hot air, then you have another heat source other than the engine. (You might have a power transistor or two mounted in the air path. On the 328, the transistor for the aircon fan speed is mounted on the evaporator to keep it cool.) Not likely, but an easy possibility to eliminate early.

 

I wouldn't have thought it was the pump as the pump only acts as a recirculating pump - I would be inclined to see if the electromagnetic valve (#38) is stuck open, from memory I think it's accessed in the passenger footwell area.
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The waterpump is used only to keep coolant flow constant through the heater core when engine rpm is low.

The electromagnetic control valve controls the heater temperature. It is powered closed by the heater control unit, so if there is a loss of power, then the valve goes to full hot.

The heater control unit looks at the desired temperature setting on the temperature control and compares this with the cabin temperature sensor and the heater box temperature sensor, and then cycles the heater valve closed for a period of time.

You can unplug the electrical connector at the valve and plug a 12v test light in its place to observe the control unit operation. With the temperature control set at full cold, the light should be on all the time, with it set at full hot, the light should be off, and with the control set in the middle, the light should flash on and off.

When there is power at the connector, you should be able attach it to the valve and feel the valve click closed.
The rubber diaphragm inside the valve can fail and allow coolant to flow even though the valve is powered closed. The guts inside the valve are the same as BMW and Mercedes, so you can buy a repair kit for the valve and repair it instead of buying a new one from Ferrari.

Brian Brown
Patrick Ottis Co.

 

The heater valve should be up under the dash on the passenger side just below the right A-pillar. The guts of the valve are the same as BMW e28 (1982-87 528e/535) (1982-88 633/635), I don't know the MBZ application, but when I worked at a BMW/MBZ dealer, I saw them use the same parts.
A good parts supplier should be able to get it for you.

Brian Brown
Patrick Ottis Co.

 

I have this same problem with my new 328. I have all of the climate controls off and there is hot air pumping out of the top dash vents. I'd like to try and diagnose it when I get home from work tonight. What should I look for? Is this something I can manually turn off (heater control valve)?

 

One thing to try is to see if you can hear the electromotor valves moving.With the engine off turn the ignition switch to the II position(dash lights)Move the Hot/Cold switch forward and back and see if you can hear the motor.Do the same with the Top/Bottom diverter switch.You should be able to hear something opening and closing.Repeat for the other side.If you dont hear anything then it will be an electrical problem,either the switch or the electromotor.
If you can hear the motors working another thing to try is calibrating the switches.The procedure is explained in the service bulletin 80-36.
http://ferrari.cdyn.com/ferrari_docs/328_bulletins.pdf

 

Thank you very much. I will try all of this and let you know how it works out.

 

Make sure and check the sensor in the dash for interior air temp. The sensor is above your left knee in the dash lower area. It has a small plastic loover entry, a two wire eletrical plug in the rear of the sensor. If that plug is removed it sends the temp to max heat. Also make sure small rubber hose is attached and small fan motor is turning with the system active.

 

Great to know. Thanks!

 

I have the same issue. Only rebuilt the valve under the dash. Didn't solve issue in my case.

I did however find out that the ducts in the center dash can be closed by turning all the way to one side. That stopped my air flow for the time being. Those, on top of the dash, and two that are supposed to blow on the feet. If you close them all it will allow you to drive without the dribble of additional scorching air.