Clutch and glow plug woes

If you get the new type plugs, yes. Don't wire the old ones like that.

Most of the later type are now self regulating normally double wound when heated current reduces to stop them self distructing.

SpringDon said:

If you get the new type plugs, yes. Don't wire the old ones like that.

Click to expand...

But don't the new ones wire in parallel not series?

Stormintrooper said:

But don't the new ones wire in parallel not series?

Click to expand...

Think you may be getting a bit too technical about this. Been changing those for over 30 years, never needed to worry about it!

Good, working plugs, wired as before on your vehicle, power going to them. Doubt there will be a problem!

I know how to do it with either and this thread is confusing me.

If your system is original and the top of your heater plugs have a ceramic disc on them and pig tails you need to wire them how god intended. They wont work any other way. They need to be controlled using the resistor coil on the bulkhead and indeed wired in series.

If you are fitting the modern type without the ceramic disc you are better using the manufacturers wiring diagram. Some recommend using the original coil as part of the circuit but some recommend you bypass it. I am sure they have very good reason for the different arrangements but thats their prerogative. These are simply wired one to the other in parallel and earth themselves.


I would strongly suggest if your not sure of the wiring changes necessary to swap systems, you simply throw away the newly purchased plugs and get modern design replacements that will be a simple straight swap.

^ what he said.

Recently, I replaced the old series wired ones with a parallell kit from Paddocks including a new ballast resistor following some sound advice. It works fine, but I have to glow the engine much longer before trying to start it. So, I had the garage check, and they claim the wiring is of the wrong dimension for the power needed... I don't know if that's actually the case, though. But I do not want to fiddle with the electrics more than usual...

Not sure why the new ones need a separate resistor as they are meant to have resistance built in each plug. Then again I'm pretty numb.

The newer style plugs (non pig tail) should be wired in parallel but without the ballast resister. The newer type plugs take the full voltage. They earth to the block when fitted so only require the single lead going from the top of each to the next in line.

The older pig tails must be wired in series and they must go through the ballast resister as they are about 1.7v each.
1.7v X 4 plugs = 6.8v
The ballast resister reduces the voltage accordingly for the above required voltage. The orange glow bulb in the dash should be a 6v bulb (just replaced mine). If you use a 12v bulb it will barely be visible.

An engine that clean deserves to start !

This post at Landrovernet.com is interesting. Apparently I am to get rid of the ballast resistor and swap the lamp. Okay, will do.