2005 Alphard 3.0ltr Petrol Heater/AC controls Totally Dead

[Will106]

Hi All

I recently installed a new Android Head Unit into my sons Alphard which was challenging as he couldn't obtain any wire adaptors to make it an easy plug in and go,

so I finally tracked down the correct wires and soldered the day away. Put it all together again and switched it on Phew! everything worked great on the Head Unit.

However the Heater controls unit that sits under the head unit screen was completely dead, no clock showing in the window and none of the push buttons did anything when pressed

As I had moved this unit out of the old Toyota Head Unit and fitted it into the new fascia I noticed the wiring to it was totally separate from the Head Unit wiring so it was simply, plug the same two connectors back in( or did I assume Wrong? ).

I took it apart again and made sure the two wire plugs was press all the way in and switched on, still dead, stripped the controls unit off the fascia and carefully took the two parts  apart and visually checked the circuit board for anything obvious like burnt marks etc and the ribbon strip connector but all looked ok so reassembled everything and powered up again with the same result the whole controls unit dead.

So I'm Wondering If any of you more experienced Members have come across this problem or can suggest anything I might try.

Many Thanks for taking the time to read this and replying if you do

Kind Regards 

Will

 

[Rojie]

43 minutes ago, Will106 said:

Hi All

I recently installed a new Android Head Unit into my sons Alphard which was challenging as he couldn't obtain any wire adaptors to make it an easy plug in and go,

so I finally tracked down the correct wires and soldered the day away. Put it all together again and switched it on Phew! everything worked great on the Head Unit.

However the Heater controls unit that sits under the head unit screen was completely dead, no clock showing in the window and none of the push buttons did anything when pressed

As I had moved this unit out of the old Toyota Head Unit and fitted it into the new fascia I noticed the wiring to it was totally separate from the Head Unit wiring so it was simply, plug the same two connectors back in( or did I assume Wrong? ).

I took it apart again and made sure the two wire plugs was press all the way in and switched on, still dead, stripped the controls unit off the fascia and carefully took the two parts  apart and visually checked the circuit board for anything obvious like burnt marks etc and the ribbon strip connector but all looked ok so reassembled everything and powered up again with the same result the whole controls unit dead.

So I'm Wondering If any of you more experienced Members have come across this problem or can suggest anything I might try.

Many Thanks for taking the time to read this and replying if you do

Kind Regards 

Will

 

 

Did you disconnect that battery before starting the work ?

 

Are there any other electrical functions that no longer operate correctly ?

You may have blown a fuse, any other function issues may help identify which fuse (if any).

[Will106]

5 hours ago, Rojie said:

 

Did you disconnect that battery before starting the work ?

 

Are there any other electrical functions that no longer operate correctly ?

You may have blown a fuse, any other function issues may help identify which fuse (if any).

Hi Rojie

Thanks for replying .Yes and my son checked every fuse especially the ones in the passenger side fuse box as I'm older, I'm not as double jointed as I once was which helps to access these fuses🤣 🤣Fuse number 14 was blown so he replaced the 10amp fuse but the control unit was still dead

Thanks again for replying

Kind Regards

Will

[Rojie]

10 hours ago, Will106 said:

Hi Rojie

Thanks for replying .Yes and my son checked every fuse especially the ones in the passenger side fuse box as I'm older, I'm not as double jointed as I once was which helps to access these fuses🤣 🤣Fuse number 14 was blown so he replaced the 10amp fuse but the control unit was still dead

Thanks again for replying

Kind Regards

Will

 

Fuse 14 is, as you know, for the Panel; 'switch illumination and air conditioner illumination'.

 

Fuses, as we all know, blow for a reason.

If your unit has become faulty, it may have blown the fuse again.

 

Despite needing to be a contortionist, it may be worth checking it again.

 

If it has blown again I suggest you now have a hard fault.

Normal approach would be substitution (which can be risky even if you have a spare) or isolation.

 

Are you sure everything else is working apart from that control panel, and what it controls ?

 

 

[Will106]

HI Rojie

I was about to fit the unit again when I thought about what you advised .and went over the sequence of events.

what would blow the fuse obviously power and the only outside power comes from the two harnesses which was working before the change out .

when I was checking the circuit board for any burn marks etc I noticed a Flat Flexible Ribbon Cable plugged into the board but I didn't go near it ,as this was the only other place that would receive power in the unit I had another look at the board and the ribbon cable I noticed it was a bit squint in the connector so I disconnected it carefully and put it back in powered it up and didn't blow a fuse and got a partial result the blowers and the clock worked but no lights or display so It looks like the ribbon cable contacts got damaged in the transfer, so I'll try and source a new ribbon and see if I get a fully working unit ,failing that  I'll try and source a complete control unit (Deep Joy 🤣🤣)once again thanks for replying  and your input

Kind Regards

Will 

[Will106]

On 5/28/2025 at 4:15 PM, Will106 said:

HI Rojie

I was about to fit the unit again when I thought about what you advised .and went over the sequence of events.

what would blow the fuse obviously power and the only outside power comes from the two harnesses which was working before the change out .

when I was checking the circuit board for any burn marks etc I noticed a Flat Flexible Ribbon Cable plugged into the board but I didn't go near it ,as this was the only other place that would receive power in the unit I had another look at the board and the ribbon cable I noticed it was a bit squint in the connector so I disconnected it carefully and put it back in powered it up and didn't blow a fuse and got a partial result the blowers and the clock worked but no lights or display so It looks like the ribbon cable contacts got damaged in the transfer, so I'll try and source a new ribbon and see if I get a fully working unit ,failing that  I'll try and source a complete control unit (Deep Joy 🤣🤣)once again thanks for replying  and your input

Kind Regards

Will 

Hi

Strange  but True, I got a text from my son saying he started up the the Alphard and he noticed all the controls were working  I don't know how,  maybe it reset its self on start up???whatever the reason it's brilliant it's all working again and hopefully puts an end to this problem, if not I'll let youse all know 

Kind Regards All

Will

PS I sourced a ribbon cable off eBay, I think it's the right one, Just in case🤣🤞👍

[Picasso]

thats great news will glad your all sorted