Overheating Light Coming On Too Early

[Vulgalour]

Car is a 1988 1.3 City X manual.

For context, the temperature rarely gets above 1/3 gauge in regular driving, and rarely over 3/4 gauge in stop-start traffic which seems totally normal behaviour to me. No physical signs of actual overheating, good compression, no coolant loss, brand new radiator and thermostat, excellent heater output etc. The cooling system appears to be in very good health and offering no cause for concern. Occasionally in the very hot summer weather we're having the temperature will got above 3/4 gauge if I'm stuck idling in traffic for a while but that can be controlled by either turning the heater on or just turning the car off and letting it cool a bit while I wait for traffic to get moving. From personal experience that seems totally in line with cars of this age on modern fuel stuck in traffic on a very hot day.

The problem is the little red flashing light that comes on to tell you that you've overheated is coming on at about 1/2 gauge. The electric fan does kick in as it should and does bring the temperature down but the light will sometimes stay on until the temperature has dropped to 1/3 gauge. Most recently, on very hot days the light will flash when the ignition is on before even starting the car, even if the engine is well below any sort of overheating temperature.

Is there any way I can adjust the instrument pack so the light doesn't come on until, say, 3/4 gauge? Or is this just a Maestro thing?

[Doctordiesel77]

It sounds as though something is amiss in the instrument panel circuitry, probably easiest to replace the clocks, I don't think there is any adjustment, but it is possible that someone on here might know how to repair it. You could fit your speedo head to replacement clocks to keep mileage right, or get an old fashioned car dealer to reset the new one

[Nick RS]

I had something similar on my 1.3 a few years ago. The overheating flashing light came on even before the engine fired. A £15 replacement ECU from eBay solved it, along with a load of other starting and running problems.

[Vulgalour]

When I got the car, the fuel and temperature gauge pack didn't work at all, totally dead. The one I've fitted is an eBay purchase, believed NOS and apart from the hyper sensitive red light seems to work exactly as it ought to.

I don't think this car has an ECU either, it's still on a carb, manual choke, points and condenser, there's nothing for an ECU to do. If there is one and I've just missed it then fair enough, maybe it has some sort of very basic system though I don't know what it would be controlling.

Not getting any starting or running problems either. First start of the day is a little slower because the mechanical pump has to drag the fuel up from the tank, after that it's first flick of the key as you'd expect.

[Nick RS]

I'm sure you're correct. Mine was an early car with an automatic choke and I think that's all the ECU did. Sorry for adding confusion.

[Vulgalour]

This might have self-fixed.

Just lately, the gauge has been getting up to halfway without the light coming on. I've been unable to persuade the running temperature to get above half gauge anyway, which is good because it means the cooling system is working as it should. I've been looking for common themes for when the light comes on too, and I found one that it might be providing the light is actually still working.

The big difference lately is the top of the dashboard isn't getting as hot. The sun has been a bit fierce down here in Kent until recently when it's become quite overcast. My dashboard is no longer hot to the touch and the temperature light has stopped coming on erroneously. I wonder if the actual issue is that the components that trigger the overheating light has simple got hot enough that its giving out false readings. Looking back through the days it was being problematic, they've all been incredibly hot days and the steering wheel and dashboard have been very hot to the touch, to the level you couldn't hold the steering wheel at times.

Beyond parking in the shade whenever I can and using the sun shade I've always got in the car, there's not a great deal I can do about it.

[Doctordiesel77]

That does sound fairly likely from what you've said, the light seems to be doubling up as a dashboard overheating lamp!

[digital efi]

Just thought that I would add to this based on my experience with my 1.3HL that I have recently put back on the road (and will be selling soon).

It has a manual choke conversion, the fuel ECU has been removed and I have rewired the temperature gauge by running a wire from the sender unit in the head (this is a single terminal sender from a Metro or late Maestro 1.3) and connected it to the temperature gauge output wire on the redundant ECU multiplug.

In normal driving, the temperature needle sits well to the left (maybe the thermostat is staying open), maybe moving up to 1/4 gauge in slower traffic. At a standstill, it will move to the middle of the gauge and the fan cuts in when the gauge moves one or two graduations to the right of centre. At this point the red light also flashes and sometimes it will remain flashing after the fan has stopped. As soon as the car is moving again, the gauge drops back to 1/4 or beyond fairly quickly.

In conclusion, it sounds similar to what Vulgalour is experiencing, so I would just put it down to ageing electronic components in either the gauge or the MFU on the back of the instrument pack.

Annoyingly, the fuel warning lamp can also flash when going round corners at anything under 1/2 a tank, but I seem to remember this was a trait on my first ever Maestro (Y reg 1.6L) back in 1986!

[Vulgalour]

Minor update on this in that it hasn't given me an erroneous reading at all since the last post. The radiator fan switch - the one that pushes into the radiator itself - has however died so that's yet another one that's failed. I'm back to using the jumper wire so the fan is permanently on which I know isn't an ideal solution but it's better than overheating in traffic. It might be coincidence that the fan switch died, it might be part of the erroneous readings somehow, I don't know. All I do know is the car seems perfectly happy now and just chugs along quite merrily whenever I need to use it.