3B Super-Glow 12/6V - Relay #1 turning off too soon (1 Viewer)

[BiasedBIOS]

G'day All, I'm trying to diagnose my super glow system. The previous owner had fitted a manual override for the #1 relay (12V) but kept the rest of the super glow system in place. For a number of reasons, I want to restore it back to original and not fit a wilson switch/any other bodge.

My first question - does 12V get applied for some period of time every time it is glowed, or is it only 6V glow if the water temperature is above a certain threshold?

The 'g, E' contacts to activate the #1 relay receive 11.5V for a split second after turning key to ignition before dropping to 11 and keep going down slowly. Consequently the relay turns on (just) with ignition and almost instantly cuts out, not allowing any 12V for any measurable (on a DMM, anyway) length of time to the plugs. Is this normal behaviour for the control voltage going to Relay #1 to drop slowly like this rather than being basically on/off?

The #2 relay system works perfectly.

All the manuals I can find don't really go into any details into how the timing computer works and how it decides what power to send at what time under what conditions.

 

[David*BJ70]

Did you change your faulty glow plug ? (https://forum.ih8mud.com/threads/3b-poor-idle-smoke-when-starting.858474/)

Replaces it, then, there a good chance that the system works properly afterwards

 

[BiasedBIOS]

I was reticent to replace the glow plugs with the manual override system still in place for fear of burning this new lot out if it didn't fix it (I have a couple of mechanically & technically illiterate people driving it) but I will give it a go changing it without letting anyone else getting to it and see if it fixes it.

 

[bj40green]

This is the explanation for a L engine but is much similar to the glow system in your 3B.
If the PO modified to a Wilson switch set up he also should have changed the glow plugs.
Wilson switch with glow controller = 8.5V glow plugs
Wilson switch no glow controller = 11 or 11.5V glow plugs.

Hope this helps. If you want the full size jpg picture (because this forum downsizes pictures to fit the screen) send me a PM with your email address.

Rudi

 

[BiasedBIOS]

Presumably not an increase in plug voltage, he left me with the advice to not push it for more than 3 seconds at a time and only when its stone cold.
Part of me thinks the PO installed this system to give these plugs more time when engine is cold because they were starting to get worn and lose their effectiveness, but in doing so manage to burn them out further.

I spent half a weekend removing all the other very questionable wiring fitted by the previous owner/s, so them leaving the plugs at 6V would not surprise me in the least.

 

[BiasedBIOS]

Update - replaced no-name glow plugs with Bosch 6V. Much smoother starting, however relay #1 is still turning off instantly.

The glow plug light on the dashboard is still lighting up for its 2 seconds or so when cold and when engine is warm will come on for less time, as expected - is there any reason why I shouldn't control the relay using the feed to the light? Obviously I'd fit a relay to the light circuit to control the relay #1, but I see no reason why it shouldn't work?