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Glow plug light staying on


Well-Known Member
Dec 11, 2010
Had the glow plug light come on for the first time ever, in 14 years, and whilst driving. Stayed on. Toggling the ignition a few times when parked eventually made it disappear after a fuel stop.

My understanding is that the glow screen runs on a timer influenced by the coolant temp, and it should only be on for about 90 seconds at most. Mine was lit on the dash for about an hour. I didn't notice any performance deterioration with the light on or off so put it down to a false fault indication somewhere, due to a very wet and snowy day and / or whilst EGTs were up around 800C most of the day towing throwing off a sensor. It stayed off. However the next day the engine refused to fire on a healthy starter and hence Fuel cut solenoid - [Leaving Land Cruiser Club] After sitting for an hour it fired up without any drama and has been fine since, so I've not been able to determine the cause of either as the condition has gone. But it is unusual that the first ever glow light indication was so close to the first ever no-start that it may not be a coincidence.

What might cause the light to stay on? I've had a look through the EWD, and RM184E, and RM172E but there's no reference to a glow screen but rather glow plugs, or the conditions for the combination lamp to illuminate.
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Do the following as soon as you can.....
Remove the R/H battery and battery box and underneath you will find the relay that controls the grid heater.... it will probably have shorted or broken.... this is a common and known issue that has caused fires .....
Your 1 HD FT will in all likely hood never need the relay so disconnect the supply from the battery + and insulate it well and you should be fine.... I have also disconnected the connector on the low draw side of the relay so it never gets any voltage under any circumstance
The relay underneath the battery box that powers the 1HD-FT's intake heater, was/is certainly an issue and needs checking but it won't bring on the light on the dash. It's just a basic relay that operates when told to and has no input to the actual operation of the cold start heater. I changed mine years ago, which turned out to be badly burnt and corroded and the only symptom was battery drain when parked up. The light on the dash operated normally on a cold start but the heater matrix wasn't actually working as the relay has stopped operating due to corrosion. I chose to replace mine and relocate it but as Grimbo has said, the engine will start fine without it.

If the heater is actually operating when the dash light comes on in your truck you should be able to see a significant drop on the volt meter as the heater pulls around 50 A.
If the heater is actually operating when the dash light comes on in your truck you should be able to see a significant drop on the volt meter as the heater pulls around 50 A.
As there was no performance impact, I presume not? I would guess 600W of heater into the intake would have been noticeable especially as the engine was already loaded, and I recall the dash voltage meter being at its usual position. Frustratingly it is intermittent and I am unsure how to recreate it.
Every days a school day as they say.....
I didn't know the glow light could do flash codes or would indicate a fault....
I would still check the relay as mine failed but unlike Towpacks it didn't drain the battery or seemingly do anything strange apart from occasionally show a big drain on the dash gauge for a mile or so after starting.... on inspection it was only a matter of time before it shorted out....
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Putting this down to a hot engine, without the exhaust manifold heat shield fitted, warming up the vacuum sensors / lines immediately above it, to the point they started to read funny. This code indicates an issue with a system that may no longer have any impact on my particular vehicle, so if the light comes on in future without performance impact then it can be investigated at leisure.

Doesn't explain the no start the following day, and doesn't appear related.