heater fan control knob problem / mondial | FerrariChat

heater fan control knob problem / mondial

Discussion in 'Mondial' started by oliv928, Feb 25, 2009.

This site may earn a commission from merchant affiliate links, including eBay, Amazon, Skimlinks, and others.

  1. oliv928

    oliv928 Karting

    Aug 14, 2008
    171
    France, Toulouse
    hi,
    in my 87 3.2 mondial i have the following problem :
    the interior heater/AC fan speed control knob acts more like a switch than a speed control.
    ie : fan is off. i turn the knob. it remains off. and suddenly, at a certain middle position of the knob, the fan runs at about max speed.
    my workshop doesn t know why.
    If someone has an idea of what to check and solution I would be very pleased.
    thanx all
     
  2. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    25,040
    30°30'40" N 97°35'41" W (Texas)
    Full Name:
    Steve Magnusson
    #2 Steve Magnusson, Feb 25, 2009
    Last edited: Feb 25, 2009
    Your AC fan blower control system is very similar to other F models of that same period -- at anything below maximum speed, the AC fan speed ECU (item 61) controls the current flowing in the b-e path of the power transistor (item "a"), which, in turn, controls the current flowing in the c-e path of the power transistor (to ground) and runs the fan motor at anything below maximum speed. When the speed control knob is turned to maximum speed, a switch inside the AC fan speed ECU closes, which closes relay "c", which directly connects one side of the fan motor to ground and the fan motor runs at full speed. The only thing a little strange in your description is that you say the full speed operation occurs with the knob "at a certain middle position", rather than with the knob closer to the full speed position. Things to try:

    1. Confirm the 1A fuse (item 62) on the AC fan speed ECU (item 61) is OK, or replace it if blown.

    2. If fuse 61 is OK (or if it keeps blowing after being replaced), I would try replacing the power transistor, item "a".

    Image Unavailable, Please Login

    If you do a search on "TR common emitter" or "TR power transistor", you should get some prior threads discussing this same issue ("only full speed works") on TRs.
     
  3. oliv928

    oliv928 Karting

    Aug 14, 2008
    171
    France, Toulouse
    thanx a lot for this precise description. I will try your check points as soon I am back home. Very helpfull and very detailed.
    I think you are right : the position which turns on the fan at max is nearest to the max than middle.
    thanx again
     
    AndreaZanolli likes this.
  4. mattboyd

    mattboyd Karting

    Dec 14, 2003
    140
    Fredericksburg, VA
    Full Name:
    Matt Boyd
    I had a similar prob in my mondial qv many yrs ago. inside the vent outlet is a little rheostat on a black shelf (actually heat sink). it gets very hot, hence the heat sink and being mounted in the airflow of the climayecontrol system.

    you can buy that part for a lot of money from the usual sources. with it will come the heat sink and everything. or you can actually look at the little rheostat and just source it. I used to work at a firm that built electronic devices so I had our parts lady get one as a smple for free. :)

    -matt
     
  5. rolindsay

    rolindsay Formula 3

    Jul 14, 2006
    1,022
    Houston, TX
    Full Name:
    Rick Lindsay
    If that "power transistor" is shot, you can replace it with a generic 2N3055, available at Radio Shack.
     
  6. oliv928

    oliv928 Karting

    Aug 14, 2008
    171
    France, Toulouse
    thanx a lot guy. You are wonderfull and so nice. I will try all this next.
     
  7. jonathan.mccall

    jonathan.mccall Karting

    Jan 25, 2008
    131
    N.Ireland
    Full Name:
    Johnny Mccall
    I had that problem on my 86 mondial 3.2 £30 fixed it!
    I think it was a servo which had blown on the circuit board of the heater speed control switch!
    Any electronic repair place will test and fix it.
    I recomend you bore out the rivets on the control unit yourself, get it fixed/checked and rerivet yourself using small washers.
    The repair centre broke my case, because they never took the time and care!!!!
     
  8. oliv928

    oliv928 Karting

    Aug 14, 2008
    171
    France, Toulouse
    I think transistor is used in further T models but not in the 3.2
    I drove the board to an electronic shop. It took the guy one month ( grr..) then He said : the triac ( SSS BD 680A P 540 / as I read on the component he shows me) is burned. He cannot have it with his seller. I try to find something on google but it seems complicated. Radio Shak is selling a lot of triads but I can't find my reference there. I don't know if SSS is a trademark, and the other figures are not very recognizable in the main elec standards.
    So I am still in the same failure.
     
  9. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    25,040
    30°30'40" N 97°35'41" W (Texas)
    Full Name:
    Steve Magnusson
    #9 Steve Magnusson, Sep 13, 2012
    Last edited: Sep 13, 2012
    By "board", do you mean the PCBA from inside the AC fan speed ECU/knob assembly or something else?
     
  10. Burch1

    Burch1 Formula 3

    May 26, 2012
    1,028
    Singapore/Carmel, IN
    Full Name:
    Greg
    What do you think it could be?
    '92 T Valeo Cab, FYI.
    Thanks,
    Greg

     
  11. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    25,040
    30°30'40" N 97°35'41" W (Texas)
    Full Name:
    Steve Magnusson
    Unfortunately, I don't have a manageable copy of the Mondial T wiring diagram (the copy in Section L of the online Mondial T WSM is just too difficult to deal with).
     
  12. oliv928

    oliv928 Karting

    Aug 14, 2008
    171
    France, Toulouse
    Hi everybody, and thank you for the interest You show in my problem. I would say You there are my last chance.

    [By "board", do you mean the PCBA from inside the AC fan speed ECU/knob assembly or something else?]

    Yes. The little board or circuit which is below the fan speed control knob. I will try to add pic there if necessary.

    Concerning the TR thread : as I said, in my EURO 3.2 the circuit is not equiped with transistor, but this TRIAD component. The electronic shop man told me this TRIAD is burned and he cannot find any new suitable. Neither me for the moment. The reference writen on the component is not proper to actual standards. ( SSS BD 680A P 540 )

    I don't know if the mondial T board is suitable in my 3.2

    The mechanical workshop where the car is maintained is also unable to find a new complete board from his supplier. I find myself a new board for £140 at www.eurospares.co.uk, but is it really worthy to buy that. Also some people told me it is not yet available, even if the site shows the part online.

    cheers and thanks again all
     
  13. mulo rampante

    mulo rampante Formula Junior

    May 31, 2011
    997
    Terra Incognita
    Full Name:
    Charles
    #13 mulo rampante, Sep 14, 2012
    Last edited: Sep 14, 2012
    Going out on a limb here: SSS is probably the manufacturer, and a BD680A is a PNP darlington power transistor. I'm guessing that the "P 540" is a production line number and/or date code. If this is the case, then the circuit is quite different than the one which uses an NPN transistor (like the 2N3055).

    I'd be surprised if they used a triac. Triacs are commonly used for switching AC currents and do not offer linear control (i.e. they're either "on" or "off"). Another property of triacs, like their close cousins SCRs, is that they have a latching action, staying "on" until power is removed in a DC circuit. It seems very strange that this device would be used in a DC motor control application where variable speed was desired. (For the electronics experts here, yes, even in a PWM controller it would be an unusual choice.)

    Is this part mounted on a circuit board, or is it separate on a metal plate? Is it a metal cylinder with a mounting flange with two screw holes, or is it a rectangular plastic part with a metal tab with a screw hole on one end and three leads on the opposite end? The latter description would fit a BD680. Also, can you visually confirm that the transistor found on other models is not present?

    A picture of the circuit board, and the device in question would be helpful.

    On another note, for those of us who have a standard NPN transistor controlling motor speed, here are a few NPN power transistors in a TO-3 case which are more robust than a 2N3055 and should substitute (similar Hfe, higher breakdown voltages):

    2N3772 (20A max collector current)
    2N5301 (30A max collector current)
    2N5686 (50A max collector current)

    For comparison, the 2N3055 is rated at 10A collector current.

    I've used 3772s many times to upgrade from 3055s. Note that the biggest reliability improvement will come from improved heat sinking, in any situation. (Note that these ratings are for an "infinite" heat sink, or close to it, in free air none of these devices will be able to dissipate much power).

    In summary:

    1) Please give us more info, photos would be helpful!
    2) A triac would be a very strange engineering decision... not saying it isn't the case, but more info would be helpful here.

    Best of luck,
    Charles

    ps if the circuit is the same as what we're used to, then Steve Magnusson's suggested troubleshooting is the path to follow, he is one of the "primary references" on these cars.
     
  14. mulo rampante

    mulo rampante Formula Junior

    May 31, 2011
    997
    Terra Incognita
    Full Name:
    Charles
    Greg: First thing I'd to is try to verify connections throughout, and measure voltages in the blower control circuit to see if they are as expected. Hopefully, your fault is not buried deep inside the dash.
     
  15. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    25,040
    30°30'40" N 97°35'41" W (Texas)
    Full Name:
    Steve Magnusson
    Your euro Mondial 3.2 wiring diagram shows that the same power transistor is used as other F models of this era, but the power transistor is not located on the speed knob ECU PCB -- nor does it seem to be the trouble in your case. You reported a little bit different symptom than what's usually reported with a bad power transistor so it doesn't surprise me that you found a different cause. There hasn't been a large number of reports of trouble with the speed knob ECU PCB, so there's been little/no prior discussion of sourcing those parts on the PCB -- I guess that you are just (un)lucky ;)
     
  16. oliv928

    oliv928 Karting

    Aug 14, 2008
    171
    France, Toulouse
    #16 oliv928, Sep 16, 2012
    Last edited by a moderator: Sep 7, 2017
    HERE is a photo of the circuit and the component. I canot confirm that it is not a transistor. Only the electronic workshop guy told me that.

    [Is this part mounted on a circuit board, or is it separate on a metal plate? Is it a metal cylinder with a mounting flange with two screw holes, or is it a rectangular plastic part with a metal tab with a screw hole on one end and three leads on the opposite end? The latter description would fit a BD680. Also, can you visually confirm that the transistor found on other models is not present?]

    It looks like the second descritpion.
    Image Unavailable, Please Login
     
  17. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    25,040
    30°30'40" N 97°35'41" W (Texas)
    Full Name:
    Steve Magnusson
    #17 Steve Magnusson, Sep 16, 2012
    Last edited: Sep 16, 2012
  18. oliv928

    oliv928 Karting

    Aug 14, 2008
    171
    France, Toulouse
    #18 oliv928, Sep 17, 2012
    Last edited by a moderator: Sep 7, 2017
    the picture above shoes the entire PCB and the subject TRIAD. The picture quality is not very good. Here is a picture found on internet of a similar looking component (plastic side). The other side is metalic.
    Image Unavailable, Please Login
     
  19. mulo rampante

    mulo rampante Formula Junior

    May 31, 2011
    997
    Terra Incognita
    Full Name:
    Charles
    #19 mulo rampante, Sep 17, 2012
    Last edited: Sep 17, 2012
    BD 680A is a proper part number according to the European Pro Electron/EECA standards, but it is for a PNP Darlington transistor, as I mentioned. Also, the "540" looks like a date code (40th week of 1985) which would make sense in a 1986 car. I really think that may be the part, based on the part number and the fact that a darlington transistor might reasonably be expected in this sort of circuit. Hopefully my reasons for thinking this will be clear from the following text.

    One way to find out would be to compare the wiring diagrams for both cars, and to see if they're identically connected. This is no guarantee though, as you would have to consider the external circuits carefully with an eye toward voltages and how any external relays operate. That really is a job for a electronics technician or engineer.

    The appearance of that part is very much like a BD680, which is found in a TO-126 or TO-225 package. (TO stands for "Transistor Outline" and it refers to the packaging materials, dimensions and so on.) The package tells us very little by itself. But since the BD680 also uses this package, or one very much like it, I would look into this carefully.

    I understand the man in the electronics shop is telling you something else, but he may be thinking it is a motor speed controller for an AC motor, which would use a triac. If someone brought me that circuit board, and told me it controlled the speed of a fan, I would also expect that part to be a triac if it was for an AC circuit. I also think that a person would need to draw a schematic diagram in order to understand how the part functions -- only then could a determination be made.

    I will try to look at mine at some point, and I'll draw a schematic for the benefit of all... but I have very little leisure time lately, so it may be a while.

    I wish you luck with this... it would be a shame to pay £140 for a complete assembly when the failed part probably costs less than a pound by itself.
     
  20. mulo rampante

    mulo rampante Formula Junior

    May 31, 2011
    997
    Terra Incognita
    Full Name:
    Charles
    #20 mulo rampante, Sep 17, 2012
    Last edited by a moderator: Sep 7, 2017
    Could "SSS" be "SGS"? I've attached a picture of SGS BD680A, note the logo. SGS stands for Società Generale Semiconduttori, they are now known as STMicroelectronics and are a big maker of semiconductors.

    The picture is from a google search, where I found GPEC S.R.L. selling these for 0.18 € each. This part is still made by ST, Fairchild and I think ON Semiconductor and should be very easy to obtain from any electronics supplier.
    Image Unavailable, Please Login
     
  21. oliv928

    oliv928 Karting

    Aug 14, 2008
    171
    France, Toulouse
    Thank You so much mulo rampante. I am quite sure You are right at all points and end up my nightmare. You are right it is SGS and not SSS. I could not read properly the letters. The pictures You send here exactly match the point. That is it !
    Thank You very very much ! You should come here and have a ride in my mondial, enjoying the new controled air flew with me ( and engine also...)
    Cheers cheers !
    This subject should be highlighted and classified as a solution to that particular problem when I have replaced and checked the system.
     
  22. mulo rampante

    mulo rampante Formula Junior

    May 31, 2011
    997
    Terra Incognita
    Full Name:
    Charles
    #22 mulo rampante, Sep 18, 2012
    Last edited by a moderator: Sep 7, 2017
    You're very welcome! I'm happy to help. But I must caution you: I think it is unlikely that part failed by itself.

    I would look for the "power transistor with bracket" that Steve mentioned, I think the BD680A is used to drive that transistor, and if the power transistor failed it could cause enough current to flow that it would damage the BD680A. A short circuit from one of the wires to the chassis or a grounded conductor could also cause the problem.

    If you find the power transistor failed, you will need to replace it with one of the transistors I recommend in a previous post. I would also inspect the wiring, especially where the wires come in contact with metal parts of the car.

    Attached is a picture of the part of the circuit in question, this is from the 1987 Mondial 3.2 wiring diagrams. Hopefully your car is the same. The control is 61 ("Air Conditioning Speed Variator"), and the power transistor is item A ("Power Transistor for Blower Motor").

    You can use an ohm meter to measure the resistance between the base and emitter of the power transistor. The orange/red wire connects to the base, and the 1.5mm yellow/green wire connects to the emitter. These are available at connector C12 pins 7 and 2. You should see a high resistance or open circuit between these two wires with the speed control module (variator) disconnected. This should be true regardless of how you connect the test leads to the connector (it should high or open with them reversed as well). If you see a resistance of just a few ohms both ways, then the power transistor has surely failed, or you have a short circuit in the wiring.

    The same test can be made between the base and collector of the power transistor, you can measure this at connector C11, pins 8 and 4 or at connector C12 pins 7 and 4 with the control disconnected. The collector of the power transistor is connected to the 1.5mm green/red wire. You should see results much like the test between the base and emitter.

    In these tests, I assume that the relay which provides full fan speed is not engaged.

    But... Instead of performing these tests, I would just replace the power transistor attached to the metal bracket, it is not an expensive part and you can replace it with something better. The tests I've described here are just what I've come up with looking at the schematic this morning and I've not actually made the measurements. Besides, the transistor is easy to replace.
    Image Unavailable, Please Login
     
  23. jimmi

    jimmi Rookie

    Jul 13, 2015
    7


    Hi there,

    i have a mondial with fan speed issue also.
    first fault i found was the fan speed switch (drivers switch was faulty) i had it repaired and i still only have max speed.

    i just want know where the AC ecu is located and does the AC system have a fan speed resistor which powers the cabin blower motor for AC.

    Any info/help would be Great.

    Regards


    Jimmi
     
  24. jimmi

    jimmi Rookie

    Jul 13, 2015
    7

    Hey there i have the exact same problem with my mondial t 89"
    the power transistor and the fan speed poteniometer have been replaced.

    I cant find the Fan speed ECU, cause i need to check the fuse (62).


    Any help is great.


    Kind Regards



    Jimmi
     
  25. porphy

    porphy Formula 3
    Silver Subscribed

    Dec 9, 2009
    1,203
    LouisvilleKY/Switzld
    Full Name:
    Randall Gatz
    Is the FAN speed ECU Bosch 1147328072? Located under the passenger foot well? If so, does the ECU need to be opened to find the fuse? I see no fuse located on top of the ECU?
     

Share This Page