Mondial t blower resistor discovery

About 18 months ago I replaced the blower resistor located inside the central dash air vents in order to fix a 'switch' like blower motor.

The frame that the resistor is attached to is difficult to re-fix if you have normal sized hands, so I ended up just attaching it with one bolt rather than two.

Yesterday the heater/AC blower started to act oddly again. The blower was set on high, even when the "Off" button was pressed. It would turn off with the ignition (unlike that other issue when the blower runs with the ignition off).

On further investigation I found that the resistor frame was loose and was occasionally shorting against the nearby metal parts, and this was making the fan run even when the 'off' button was pressed.

I refixed the resistor frame with 2 bolts and this has cured the issue.

Hopefully this will help someone trying to trace an intermittent blower motor issue like mine.

 

Hi Brand new here, I just bought a Mondial QV (1985) its being shipped to me next week! however, dealer informed me the Heater Blower motor is not working. what should I prepare to deal with on this issue? Thanks Bradley

 

There us a fuse just beside the switch. When this is shot, you have the blower working only at maximum speed. If blower isnt working at all, you have to deal with bad connection of ground or power supply. Just check first if you have maximum blower.

 

Guido, is this true for the Mondial-t as well ? Mine is only blowing at maximum speed. Where is this fuse located in a t model ? Tx.

 

Stef, ge moogt dat ook in het Nederlands vragen ....jammer genoeg niet hetzelfde voor de mondial t. Ik vermoed dat de fan speed regulator een probleem heeft. Misschien eens afnemen en zien of ge die open krijgt. Mogelijk de contacten vanbinnen gecorrodeerd

 

Translated:

Stef, you can also ask that in Dutch .... unfortunately not the same for the global. I suspect the fan speed regulator has a problem. Maybe take it off and see if you can open it. The contacts inside may be corroded


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Bedankt Guido, I know you are from Belgium, but I posted the question in English due to the international audience ;-)
I will check the regulator after her winter sleep, I remember removing the panel when I had to clean the antenna-switch. I will check a few photo's I made at that time.

 

Yes, thanks...is your Global doing fine also !

 

No, the design of the fan speed control unit changed over the years, and, by the late 80s, the small fuse had been eliminated from the 140151 unit that your Mondial t uses. Much more likely that the power transistor in the power transistor assembly, item 13, here:

https://www.ferrariparts.co.uk/diagram/ferrari/mondial-t-coupe-cabriolet/150-air-condition-set

has failed. If you do a search on "AC fan power transistor" you'll get a lot of prior threads with suggestions of (better) power transistors that you can buy and use as a replacement (rather than buying the whole assembly). The usual repair strategy would be to replace the inexpensive power transistor first, then, if no joy, work on, or replace, the more expensive fan speed control unit 140151.

 

This is the power resistor you need to fix the fan speed it is not the switch
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Thanks so much for that info! my Mondial will be here tomorrow. However, it is not a “T” it’s a 1985 quatrovalve same strategy? Help is much appreciated.

 

Also, where is this part located on the car?

 

Yes, Mondial QV also uses a power transistor, but I believe your fan speed switch is also the older type that does have the small 1A fuse in the 61112300 speed control switch itself that will also give the symptom of "only full speed works" when it is blown (the fuse is under the slotted cover on the side):

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The power transistor is typically mounted somewhere inside the main cabin air outlet duct so it is cooled by the flowing air when in use (but sometimes Mechanics will relocate it during replacement for easier future replacement). Item 54 here:

https://www.ferrariparts.co.uk/diagram/ferrari/mondial-qv-coupe-cabriolet/122-heating-system

 

It should be att.to the air duct under the dash the cost 2-3 $ very cheap on e bay.

 

You Rock! thanks so much. its landing in my driveway tomorrow. Here we go!

 

Got it last night, trucked from Colorado to oakland, Covered in dirt/slush/rain water. It won’t start, checked battery, it’s OK. Ran fine when it left Colorado. Should I try a rolling start? Jump the starter? Such a bummer.

 

Do the headlights work and/or other electric devices like the clock? If not, the ground switch could be switched in the 'off' position for the transportation.

 

Jeka
Hi, thanks for jumping in, everything lights up, but will not crank. I guess I could tap the starter, then jump the solenoid? It feels like a starter issue to me.

 

Hi where is the ground switch located?
Bradley


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If everything lights up (also during cranking?) the ground switch should be good. There could be a problem with the ignition switch, connectors, wiring or the starter motor. The circuit itself is very simple, the ignition switch switches 12V to the solenoid to activate the starter motor. If all the ignition switch operated devices are working then there is 12V at the switch.

 

This is the circuit.
View attachment 3047292

 

Likes like that’s long gone, lots of wire splices all over the place [emoji37][emoji21]


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When ground switch is corroded, you have a current drop and the car will not start....are the rest still working. First make a direct connection battery to chassis.

 

Thanks for taking the time to help me with this, let me investigate and get back to you with what happens.