Heater fan help

[davidd]

Morning,

My griff 500 cabin heater fan is now permanently on.

Was fine 10 days or so ago, then it decided to turn it self on with the ignition. It was low speed, almost like it was just turning over. I could still press the switch to make it come on properly, control the speed.

A couple of days later and it is now just on full power as soon as the ignition is on.

I've checked the lower dash, all looks ok. If I disconnect the ribbon cable the fan still keeps going.
The connections into the control box look ok.
I can disconnect the plug in the passenger footwell and it stops, plugging in obviously restarts it.

Before all this I disconnected the battery a couple of times as I was checking for parasitic drain and adding a ctek charging cable, so i do wonder if I disturbed something somewhere.

Any ideas?

Many thanks

David

[davidd]

I've done a little more investigation.

If I unplug the big connector from the back of the black control unit (under the radio) the fan keeps going on full power.

I noticed that there are two lots of live and two lots of earth going into the connector....



It there another switched power on a relay I should be looking at?

Thanks

D

[Adrian@]

davidd said:

I've done a little more investigation.

If I unplug the big connector from the back of the black control unit (under the radio) the fan keeps going on full power.

I noticed that there are two lots of live and two lots of earth going into the connector....



It there another switched power on a relay I should be looking at?

Thanks

D

Can I suggest you open the controller, look on the back of the board for burnt out tracks.
IF this is case the motor is starting to fail and resistance is being feed back to the controller.

Again if this the case, get a soldering iron out ...you may need to create links of burnt out tracks/replace the plug/connections...start double checking earths and maybe replace the motor (strip and refresh). A@

[davidd]

Adrian@ said:

Can I suggest you open the controller, look on the back of the board for burnt out tracks.
IF this is case the motor is starting to fail and resistance is being feed back to the controller.

Again if this the case, get a soldering iron out ...you may need to create links of burnt out tracks/replace the plug/connections...start double checking earths and maybe replace the motor (strip and refresh). A@

Thanks, but why would it still run when the big connector at the back of the control unit is disconnected?

[Geoff-Griff500]

These can take so long to fix. Mine was on all the time so took it to my dealer who has all the equipment to do this in a fraction of the time.
It now works and even the lights come on to say it's working.
Sometimes tinkering around is great, electrics, nope, unless that's your expertise.

[davidd]

Geoff-Griff500 said:

These can take so long to fix. Mine was on all the time so took it to my dealer who has all the equipment to do this in a fraction of the time.
It now works and even the lights come on to say it's working.
Sometimes tinkering around is great, electrics, nope, unless that's your expertise.

This is a very fair point. I thought I might have disturbed something when putting a ctek connector on the battery which is why I started to look into it.
I do as Adrian suggested and try and get the box out this evening and see if there is anything obvious wrong with it. Then it will be beyond me.

The car had a new fan 2 years ago so I wonder if this issue is related (as per the previous post).

If I get stuck then it will be back to Mat Smith.

I have headlamp bulbs to do this weekend, fingers crossed that goes a little more smoothly.

[davidd]

Right I have taken the board out.

I’m not sure there is anything obviously wrong but I m no expert.
Any ideas? The wiring is tight in the car so hard to test in situ.

Edited by davidd on Thursday 30th October 18:11

[Adrian@]

It does look good, (for 25+ years). I would gently press the board parts whilst looking at the rear of the board checking for cold solder joints, especially the mosfet (look up failure of the mosfet, as it is most likely to fail with the motor then running at full power) and the two main wires, check the loom/plug females and the earth to the chassis hidden behind the carpet down to the chassis. A@

Edited by Adrian@ on Friday 31st October 15:45

[davidd]

I've had a chat with Python racing, explained the symptoms and how they progressed. They think the mosfet is the issue so I've send the board to them for diagnosis.

I'll update when I get some feedback from them.

[Adrian@]

A good call if you are not up to swapping one in yourself. (I had a diode to replace last time too). A@

Edited by Adrian@ on Friday 31st October 11:16

[davidd]

Adrian@ said:

A good call if you are not up to swapping one in yourself. (I had a diode to replace last time too). A@

Edited by Adrian@ on Friday 31st October 11:16

I did consider swapping it myself but couldn't get one until mid nov.

He'll be able to test the rest of the board so hopefully will get it sorted. In the meantime I can try and work out what the other boxes behind the dash are!

Thanks

[Adrian@]

davidd said:

Thanks, but why would it still run when the big connector at the back of the control unit is disconnected?

I meant to answer this ...as I understand it, the motor is live and the earthed via PWM on the board (Paul Smith designed [e-mail] or call [phone]) This is that later of two heater control boards. (you have mentioned Python in your post who also work on them). A@

[davidd]

Adrian@ said:

I meant to answer this ...as I understand it, the motor is live and the earthed via PWM on the board (Paul Smith designed [e-mail] or call [phone]) This is that later of two heater control boards. (you have mentioned Python in your post who also work on them). A@

Thankyou. I did try Paul Smith but he didn't answer so gave Python a call.
I'm going to tidy up the wiring a little to make it a bit easier to get the box back in. I don't suppose you (or anyone else) can tell me what these boxes and relay are for so I can label them?

[Adrian@]

The grey one is the central locking relay ...TBH I would start a new topic. (it will create it's owm searchable item).
A@

[davidd]

Adrian@ said:

The grey one is the central locking relay ...TBH I would start a new topic. (it will create it's owm searchable item).
A@

Good plan, thanks…