factory dash clock losing power - door open warning light not working - clock display goes off when any door open (1 Viewer)

[sunrk]

This has been happening for a while but I noticed it's got to the point now where instead of the clock seeming to randomly have no power now if any door is open the clock goes off (display goes dark) and the red door-open warning light doesn't light up at all. The clock still seems to be 'stopping' at random as well (ie. I'll turn on ignition and the clock's 'lost' it's time).

Note it's a RHD 80, with no door chime thingy. I am trying to understand the schematics and how the door switch and warning light circuit interacts with the clock circuit.

My feeling is that there's an earth wire going/gone bad. The door switch and interior light circuit is fed from the 'dome' fuse which is itself fed from the power junction box (which I think is the one in the engine bay).

The clock has power from two places - one is a feed that enables the display via the ignition switch the other is what I think is it's permanent power (to keep clock 'ticking') from the 'dome' fuse.

I don't have a spare clock module otherwise I'd just replace it and see if that's the answer. Clock for my 80 is 83910-60040. It's the basic one with only three buttons. Amayama today is quoting about A$430 to get a new one! Can get used ones for about A$100.

I've closely inspected the two aggregated earth points at the inside bottom of each a-pillar and all is good. Before I completely pull the dash fascia and get at the wiring to the instruments, clock, etc. is there anything else worth inspecting?

Craig.

 

[landcrshr]

Have you noticed any other weird problems like maybe the dome light staying on with all doors closed?

I remember seeing a problem like this and the culprit was the wire junction connector you mentioned. In a LHD 80 it's located somewhere behind the gauge cluster (combination meter). Not sure if your wiring is a mirror image or not.

LHD diagrams for reference:

Hope this helps.

 

[sunrk]

Thanks. Only other thing has been occasionally flickering dome lights but I fitted LED panels to those a bunch of years back so could be unrelated.

I noticed the pair of diodes showing in the circuit and somewhat suspect that to be the problem but I can't locate them.

In the Toyota factory manual RM184E there are schematics at the back so I'm studying the ones for the interior lights and the clock. They're much clearer and more detailed that the ones in the Max Ellery book.

The common power to both interior light and clock circuits comes via the 'dome' fuse and connector EA1.

The clock has secondary power (enabling the display?) via the ignition switch and the 'cig' fuse. It's earthed to the right and left side a-pillars after J3 junction connector.

Door switches all earth direct to the body. They earth a connection to the earth side of the door open light via diode block D8 but I can't find that device anywhere. There's no ignition key cylinder light relay as there's no light being a DX base model.

Fidding with the tail light control relay doesn't change the behaviour. I have taken out the RHF (drivers) door switch and manually jumpered it to the body which replicates the problem - dome lights operating property but clock display goes off and door open light not working.

Hmmmm

 

[jonheld]

This has been happening for a while but I noticed it's got to the point now where instead of the clock seeming to randomly have no power now if any door is open the clock goes off (display goes dark) and the red door-open warning light doesn't light up at all. The clock still seems to be 'stopping' at random as well (ie. I'll turn on ignition and the clock's 'lost' it's time).

Note it's a RHD 80, with no door chime thingy. I am trying to understand the schematics and how the door switch and warning light circuit interacts with the clock circuit.

My feeling is that there's an earth wire going/gone bad. The door switch and interior light circuit is fed from the 'dome' fuse which is itself fed from the power junction box (which I think is the one in the engine bay).

The clock has power from two places - one is a feed that enables the display via the ignition switch the other is what I think is it's permanent power (to keep clock 'ticking') from the 'dome' fuse.

I don't have a spare clock module otherwise I'd just replace it and see if that's the answer. Clock for my 80 is 83910-60040. It's the basic one with only three buttons. Amayama today is quoting about A$430 to get a new one! Can get used ones for about A$100.

I've closely inspected the two aggregated earth points at the inside bottom of each a-pillar and all is good. Before I completely pull the dash fascia and get at the wiring to the instruments, clock, etc. is there anything else worth inspecting?

Craig.

Check/replace the DOME fuse.

 

[sunrk]

Dome fuse all good. Cig fuse all good. I do need to check more though and just don't have the chance to pull the dash completely apart to get instruments out, the fascia, etc. and get at plugs at the back of everything. Otherwise the electrics are good, and everything else function properly. I did notice that the aftermarket LED light panel in the dome light has a couple of LED's that stay 'half on' when the doors are all closed and the light (which is in a new genuine Toyota light housing) set to 'door'. So before I rule it out I want to replace the light panel with a different sort of lamp but the schematic doesn't appear to be giving joy.

What the light behaviour could tell me is that the light circuit is getting power (but at a low voltage) when it supposed to be getting no power (because the doors are closed meaning no door switches are earthing to the body)..

 

[landcrshr]

Have you noticed any other weird problems like maybe the dome light staying on with all doors closed?

I did notice that the aftermarket LED light panel in the dome light has a couple of LED's that stay 'half on' when the doors are all closed...

Yeah, I had a feeling.

What the light behaviour could tell me is that the light circuit is getting power (but at a low voltage) when it supposed to be getting no power

Right, it tells you that current is flowing where it shouldn't, and it can actually be caused by an open circuit.

What might be going on is that something on the DOME circuit, like the clock, has lost its +12V feed and is now feeding through the dome lights when they're not grounded.

Here's a diagram of how that's possible:

 

[sunrk]

I'm still suspicious of the diodes but still haven't found where they are either. But yes I def need to pull the dash fascia and check all that wiring. Open circuit is a possibility.

 

[YMT]

I would start basic, before pulling dash apart. Check grounds (PO said already done). Next, check harness for visible wear, especially where feet usually are. Don't forget, the pigtail harness that goes through the grommet to each door. When these wires wear, you can get frayed wires contacting others (I've had similar and it ended up being the door pigtail.)

Are there aftermarket electronics wired under the hood? If so, isolate those for troubleshooting.

 

[landcrshr]

The diagram I posted above also explains why the clock shuts off when you open the door. Measure the voltage on the clock, then you'll know.

 

[sunrk]

Ok I've taken the LED panel 'bulb' out of the front dome light (middle one has a broken switch so it's already out), and measured voltages. In 'door' I get 11.47 with the drivers door open (light activated), in 'light (bypassing the switches) I get 12.49. No issue there.

In 'door' when I press in the switch on the b-pillar, the voltage is 6.48, and if I switch the light to 'off' I get some really strange millivolt reading up to 0.5 volts that varies all over the place. That explains why the light is 'partly on' when it's not meant to be.

Now the middle dome light is not original but is a genuine toyota light identical to the front one I wired in myself about 7 years ago. It links directly to the wiring to the front light. I can't think of any reason why that wiring will be the issue. The lights get their earth via crews into the roof structure.

Can't pull the dash out to get at the clock module and it's wiring at present (that's for tomorrow if it's not raining).

 

[sunrk]

Ok, finally got a few free hours on a sunny day. I've pulled out the wiring for the lights in the roof to double-check the wiring I added for the second light (not factory-fitted in the DX's) is good, and it is. Starting on dash fasica removal next. Clock does not light up at all now btw.

 

[sunrk]

Someone in the Lcool 80 series forum suggested I check for wiring damage (corroded contacts/terminals in connectors) due to windscreen water leaks at the bottom of the left side A pillar. There's a lot of wiring there (including a lot not used because my 80 has no power mirrors or power windows etc.) but apparently the dome light wiring runs via that pathway. I couldn't figure it out 100 pct from the Toyota FSM schematics but will try again.

------

Ok, I've found the connector at the a-pillar for the dome lights - easy to find actually. Came apart easily. No damage/decay from getting wet. I fitted two new 31 mm jw speaker LED festoon lamps to the dome lights and they both work. With ignition on and door open clock is off. With door switch pressed to simulate door being closed the clock comes on (but showing the default 1:00 time not actual time). Door open light in the instruments isn't lighting up.

I might try to get a second hand working clock before I pull the dash fascia and examine the wiring behind it. A brand new clock module is like A$350 from Japan. Ouchy!

So I'm still suspicious of the clock, the wiring to it, and those myterious diodes that show on the schematic but I've not been able to locate yet.

 

[sunrk]

Haven't solved this. Going to require dash disassembly to get the fascia out and go from there. I have a spare used clock module now just in case. New ones are sky-high priced!