Getting used to things

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R

RangerSi

Member
Posts
50
Location
Colchester
Soooooooo, my new Disco. The digital heater controls. They seem to work fine except the fan speed.

On the lowest setting there's barely a waft from the vents, turn it up one and these not a great deal off difference and so on until the fastest speed. Then, it's like a hurricane (ok, I'm exaggerating) but......

Is this what the heating system is like on a 99 td5, or is mine broke?
 
brianconwy said:
I have just replaced the transistor in mine - less than a fiver, if you don't mind soldering.

http://www.ebay.co.uk/itm/MJ11016-TRANSISTOR-/322197598204?hash=item4b04792ffc:g:chkAAOSwxH1T8hRz
Click to expand...

For that price it's worth just keeping one in the bits and pieces box, just in case it's needed.
From my experience, unless I do get a spare now, when I eventually come to need one the damned things will be obsolete and totally unobtainable, and anyway, while I've got a spare, the likelihood of me ever needing it has now deminished to almost nothing.
 
So....... today I changed the resistor as per Brianconwys advice. And nope. Still the same Unless my soldering is rubbish (it looked ok)

Any thoughts?
 
brianconwy said:
I drove the car and checked everything was working before screwing the pack in place and the heatsink was too hot to touch for long.
Click to expand...
If it's like the others I've looked at from other makes of vehicles, the fins on the heatsink should be in the cold airflow to keep the resistors or in this case the transistor working within normal operating parameters.
A TO3 transistor outline can sometimes (but not often) get inserted into its working position backwards, also the little insulating washers and the mica washer, if necessary, can get lost or incorrectly fitted which can lead to a faulty installation or repair.
 
There's not too much to the faulty unit. And it only goes in one way as the screw holes don't line up otherwise, so I doubt it's gone back wrong. Could I have soldered the transistor the wrong way? I didn't notice any sides etc.

I'll take it out of its position and go for a drive tomorrow to see if it gets hot.
 
Is there anyone in or around Colchester with a working one that's willing to do a swap test at all? Don't want to fork out for another unit if it's not that.
 
In a hope that I can help you understand what's going on here, I have produced one of my by now infamous hand drawn diagrams.
I've tried to work out the circuit from reading the description and the wiring diagrams in RAVE.
76 squadron 2.jpg

The power transistor is an NPN type and can be thought of in this case as a remotely controlled variable resistor in series with the blower motor and controlled from the air-con ECU. The green wire from the ECU (C0793-1) to pin 3 on the transistor housing carries the base current which controls the transistor.
Testing the circuit might be a little difficult and might require the use of an oscilloscope, depending on how the transistor is controlled.
Essentially there are 31 speed settings (depending upon the external conditions "observed" by the air-con sensors) sent from the ECU to the power transistor which might be just various changes in the DC voltage on pin 3, in which case it might be measureable with a voltmeter, however it might be a system called pulse width modulation (PWM), in which case only an oscilloscope can be used to verify the control signal from the ECU.
The likelihood is that the fault exists either with the power transistor which is exhibiting a short circuit condition between the collector (C0858-1) and emitter (C0858-2) terminals of the transistor or the control signal from the ECU is being driven to a full 12 volts by a fault in the ECU resulting in the transistor being driven hard on.
The wire from the power transistor housing (C0858-4) and going to the ECU (C0792-8) signals the ECU that the blower motor is online and ready to be controlled and also provides a feedback signal to the ECU.
Practically, the best way to diagnose the problem would be substitution with a known good device, but if everything has been done correctly when replacing the power transistor in its housing, then sadly it looks like you might have a problem with the ECU.
 
Last edited:
Assuming that the MJ11016 transistor is the correct one, I haven't checked the type myself, then the case will be the collector terminal and should be connected to the motor. The emitter terminal is one of the pins and should go to ground. The other pin is the base terminal.

I have only worked from the data sheet for the transistor and the wiring diagram and description given in RAVE.
Untitled.gif
 
brian47 said:
In a hope that I can help you understand what's going on here, I have produced one of my by now infamous hand drawn diagrams.
I've tried to work out the circuit from reading the description and the wiring diagrams in RAVE.
View attachment 116240
The power transistor is an NPN type and can be thought of in this case as a remotely controlled variable resistor in series with the blower motor and controlled from the air-con ECU. The green wire from the ECU (C0793-1) to pin 3 on the transistor housing carries the base current which controls the transistor.
Testing the circuit might be a little difficult and might require the use of an oscilloscope, depending on how the transistor is controlled.
Essentially there are 31 speed settings (depending upon the external conditions "observed" by the air-con sensors) sent from the ECU to the power transistor which might be just various changes in the DC voltage on pin 3, in which case it might be measureable with a voltmeter, however it might be a system called pulse width modulation (PWM), in which case only an oscilloscope can be used to verify the control signal from the ECU.
The likelihood is that the fault exists either with the power transistor which is exhibiting a short circuit condition between the collector (C0858-1) and emitter (C0858-2) terminals of the transistor or the control signal from the ECU is being driven to a full 12 volts by a fault in the ECU resulting in the transistor being driven hard on.
The wire from the power transistor housing (C0858-4) and going to the ECU (C0792-8) signals the ECU that the blower motor is online and ready to be controlled and also provides a feedback signal to the ECU.
Practically, the best way to diagnose the problem would be substitution with a known good device, but if everything has been done correctly when replacing the power transistor in its housing, then sadly it looks like you might have a problem with the ECU.
Click to expand...


Blimey! You know your stuff.

Thanks for the concise reply. I'll try and locate a known working unit and see if that helps. If not, can the fault with the ECU be rectified with a nanocom or similar device?

In the meantime, I'm going to redo the solder connections on the transistor, but clean up the side with the fins really well first. Maybe the connection to the collector isn't good enough?

I'm a complete novice, so this is a steep learning curve for me.

Thanks again.
 
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