Blinking Thermostat Pilot Lamp!

[Bullstrode35]

No, I'm not yelling ...

It's just that the thermostat pilot lamp on my Branson 6530 has started to flash after I've been driving it for an hour or so. I don't think it's weather related - it's between about 8C and 18C most days now (in Oz). The manual says it should light up in cold weather when starting which is fine; but says nothing about blinking later. Could it be a warning of some sort?

Anybody got any suggestions please?

cheers,
B35

 

[Dave M7040]

I think you mean Thermostart which provides a small flame of hot air into the engine intake when trying to fire up in colder weather for engines that do not have glow plugs.
If you can post a wiring diagram I might be able to make some suggestions.
From a google search an explanation.

Inside A Yanmar Thermostart

What is a Thermostart?

A Thermostart is a very efficient glow plug used in most of the Yanmar tractors. Instead of relying on just a heating coil like other glow plugs- this unit also drips a small amount of diesel fuel onto the red hot coil. This produces thick smoke, lots of heat, and occasionally small flames. All of these things help the engine to start in the coldest weather.

So how does it work?

The fuel line is connected to the thermostart through the fitting (A). The fuel is not allowed to leak out because the set screw (C) is screwed up into fitting (A) and is tightened up against the check ball (B) - forcing it against the ball seat deep inside fitting (A).

When you are ready to start the tractor the glow plug gets energized through the terminal (D) and heats up the element (F). This causes the hollow tube at the bottom of (A) to expand. When the tube expands it also pulls the set screw away from the check ball (B) because the set screw is threaded into the tube that is expanding. This allows a very small amount of fuel to drip down onto the heating element which starts to smoke and burn.

Why do they go bad?

Over time the thermostarts, just like any glow plug can go bad. This is typically because the heating element, which is sort of like a very heavy duty light bulb, burns out. The check valve can also start to leak over time. Running the thermostart for too long (over 10-15 seconds) at one time can also damage it.

Priming A new One.

It may be necessary to bleed the air out of a new thermostart in order for it to start producing smoke and fire. This is done by installing the new thermostart & filling the reservoir bottle with fuel. Then cycle the thermostart on 10 seconds then off 30 seconds. It may take 10-20 cycles to bleed the air out of the line & thermostart.


Dave M7040

 

[Bullstrode35]

Hi Dave M7040, thanks for your swift response.

In reply, attached is an extract from the 6530R's Operator's Manual for the the glow plug system which I think covers the thermostat pilot if that's the same as the 'Preheat lamp (meter assembley)' shown on the right of the circuit diagram. Whilst the diagram expands when clicked, unfortunately, my original is quite a low grade picture so the following is as good as it gets.



However, whilst searching for a better copy I did also come across some diagrams (with no real explanation) which suggest that perhaps the hot air blower comes on again - although I wouldn't have thought it gets cold enough here for that. It doesn't specifically say the thermostat pilot light then blinks but maybe that could be part of the answer?



cheers

B35

 

[Dave M7040]

B35
I have printed out and looked over the material you provided. As you note, no explanation of how the system is to work is provided.
The "Glow Controller" seems to be the place where the logic decisions take place.
Can you advise when the pilot lamp also known as the "Pre-heat lamp heater assembly" normally comes on.
For example, do you do something to turn on the glow plug by perhaps a position of the key or does it happen automatically.
By way of comparison to make my request clearer, on my Kubota, if the engine is cold from sitting in cold weather, a light will appear on the dashboard when I turn the key on but before I reach start. This tells me to turn the key to a position which activates the glow plugs and to keep it that position until the light goes out at which point I start the engine.
I am trying to determine if this light is telling you to do something or if something is happening automatically and the light is your notification.
Can you advise on the make and model of your engine.
Dave M7040

 

[Bullstrode35]

Hi Dave M7040,

Thanks for your comments. Much appreciated. In response ...

My Branson 6530R has a Cummins B3.3 engine - one of the attractions of the brand.

When started from scratch, the key first moves to On, when the Thermostat Pilot Lamp lights up for say 8 seconds in cool weather (also the Charge Pilot Lamp and the other usual ones). Next, when the Thermostat Pilot Lamp goes out, I move the key to Start and the engine fires up ... totally reliable, never failed (- I guess I should touch wood now).

The Thermostat Pilot lamp only started blinking after about an hour's run. I'm next due to use the Branson for a few hours in a few days' time and will then be able to see if it blinks again. Today, for the few minutes it turned over when test starting, there was no blinking. Maybe it is communicating that the air pre-heater has clicked in?

cheers,

B35

 

[Dave M7040]

B35
Finding info on the engine glow plug on the Branson web site is next to impossible.
From searching other posts I learned that the temp sensor may be located in the thermostat housing below the thermostat.
Another member said he had had to clean all the terminals in the system to get the light to operate properly.
Dave M7040