Yikes, you mean the heavy wires that normally route through the relay are now connected directly to a switch in the cab? not good.

No, 6V is not normal. 8-10V is about what you expect depending on conditions. In colder weather, the voltage sag of drawing that many amps for the glow plugs gets worse, but 6V is pretty low. Sounds like there may be some weak connections that are causing voltage drop. Also see what the voltage right at the battery is to see if they are indeed above 12V.

 

David85, Thanks for your response-He has 12V at the battery & yes the two heavy guage yellow wires are connected to a momentary ON/OFF switch in the cab on the dashboard. When pressing in the dashboard "switch" 6 volts appear at the wire leading to the Glow Plug relay.

I do not believe cold weather is a problem here in South Florida. "Cold" weather means we wear socks.

 

LOL, point taken regarding cold weather.

Trace the heavy wires back through every connection and refresh them. Pull the connectors apart, clean off any corrosion and also make note of any burning at the prongs in the case of a clip in connection. When glow plugs are pulling amps through that wire, all the connections need to be pretty much perfect, otherwise voltage and amps will bleed off along the way.

That switch is a fire hazard if it is indeed running the full amps of the glow plugs through it.

 

marybeth,
Welcome to FTE and the IDI diesel forum.

The thing is, the glow plug system draws 200 amps.

That must be a big switch to handle 200 amps in the cab or if not the switch is what is dropping the voltage.

A relay is the only way to switch glow plug power.

What is wrong with the original relay/controller?
Or how is the glow plug system acting when it is run with the stock controller?

 

Not sure what is wrong with the stock controller. The truck has all kinds of wire in the engine bay from Home Depot, Radio Shack, even home extension cords.

The truck takes a few tries to get started. He is bringing the truck over Friday so I will clean apart all the connections to see if it solves the 6 V drop.

Thanks for all the help!

 

This is a stock controller/relay with the cover removed.



It should be bolted to the center rear of the intake manifold back at the firewall.

Power to the relay from the battery, then power to the glow plugs from the relay.

Find out if that piece is still on the engine.

Using something like a 20 amp momentary switch to handle a 200 amp load is asking for a fire.

Like can my truck catch on fire, please please please can my truck catch on fire.

 

David-I did see the relay on the back of the intake manifold ( used your previous posts to find locate and ID the GP relay-Thanks)

It did cause me concern that the two heavy guage yellow wire were disconnected from the GP relay-run thru the firewall to a momentary contact switch on the dash-then back to a connection on the GP relay.

And yes the monentary contact switch does get REAL warm when depressed (I guess 200 Amps will do that)

On your photo what is the yellow wire to the right of the yellow wire? Is that were the two yellow wires my friends truck has going to the switch are supposed to be ?

 

Marybeth, There is only one small yellow wire on the controller and it goes on the contact at the top of the slinky. The small green wire goes at the bottom of the slinky. Dave's picture shows a yellow line, where the two large yellow wires connect to the controller.

Gary

 

Heres a wiring diagram that might help