Glow Plug Relay or Relay timer?

[brokenknee]

Glow plugs are not working. I checked the glow pugs and they are showing 12.6 volts, which my internet search shows they should show they are good. While trying to pull off the wire clip the cover of the relay came off. If I manually trip the relay the light comes on and will stay on until I release. I am not sure if that means the relay is good or bad. On one site it said if you have power it is good.

This is on a cub 30HP. At 85 bucks for the timer and 76 bucks for the relay I would like to try to figure out which it is.

Thanks for the help. I spent about 2 hours last night doing a search and I am not sure I understood some of the trouble shooting process.

 

[DANOCHEESE]

THis set-up should work like this. When you turn the key on the timer circuit causes the raly to close and energize the glow plugs. When the timer circuit exspires the relay will open dropping power to the glow plugs

Why do you think your glow plugs do nto work? The light does not illuminate?

 

[brokenknee]

The light does not come on, but when I turn the key on the relay does not energize. The cover came off when I was trying to disconnect the wiring, I energized the relay manually (I pushed the lever over) the light came on. I then started the tractor and she fired right off.

 

[brokenknee]

Will the timer prevent the relay from energizing to begin with?

 

[DANOCHEESE]

Yes. Before you buy a new timer relay Look for voltage to the timer. This could be as simple as a blown fuse.

When the key is turned the timer gets voltage to one side. this allows it to work. Providing voltage to the actually Glow Plug relay. When the timer relay ends it cycle, the glow plug light and glow plugs go out

I have seen simple push button switch used to get around the timer real. Hold it in for 15 seconds and go. Cheaper than a new relay timer.

THis advice and three dollars will get you a beer at the Becida tap

 

[brokenknee]

There is voltage at the relay it just isn't pulling in to make contact.

 

[PILOON]

If you read 12 volts at the glow plug it should work as it is powered and other end is grounded.
The 'real test' is remove the plug and apply 12 volts to the grounded plug and it will glow.
If it does not get hot it is then shot A plug will read (Wire disconnected) somewhere in the very low ohms range (like under 10 ohms)
When you say you have 12.6 volts at the plugs with no heat then I strongly suspect that they are shot.
A plug drawing current will drop the voltage somewhat below the battery voltage and 12.6 is a good reading for a charged battery, with plugs drawing current you'd expect a voltage drop to as low as 10 volts.
A faulty timer would have caused that to happen as they probably stayed on for a long period of time.
Sorry, but I think all plugs are toast as well as the timer that controls them.

Your cheapest repair is new plugs and a simple HD switch to power them and counting off about 15 seconds of applied voltage.
If the engine does not start after 15 seconds you repeat and maybe go 20 seconds. etc etc.
I ran a GMC with that arrangement for years as the timer was very $$$.
Because of high current a simple relay capable of the current draw and cheap push button switch is one way to go.

The only time there should be voltage at the plugs is when you are in heat mode, that is why I say your plugs are shot. Also as stated while heating the current drop is significant but you still read 12.6 volts; ergo shot plugs (and whatever else caused that to happen).

By fluke the only cheap and easy fix could be serous corrosion at the plug contact points that would prevent good continuity.
Slacken the nuts and wiggle the contacts on each plug, re tighten and touch to see if they heat. Voltage drop is also an indicator.

Good luck!

 

[brokenknee]

I should clarify my 12 volts at the glow plugs, this is with the positive side of the meter to the battery positive and the negative lead of the meter to the glow plug. This is one test that I saw on the internet. I know the glow plugs work as when I manually energized the relay the light came on and when I went to start it, she fired right up.

 

[PILOON]

I should clarify my 12 volts at the glow plugs, this is with the positive side of the meter to the battery positive and the negative lead of the meter to the glow plug. This is one test that I saw on the internet. I know the glow plugs work as when I manually energized the relay the light came on and when I went to start it, she fired right up.

OK, so plugs are good.
Timer is activated by ignition key when turned to left.
Broken line from ign to timer or bad ign switch. (read that that is common on some tractors)
New ign switch is possible cure or add a manual separate switch to activate the timer control.
Good luck, have fun.

 

[DANOCHEESE]

HUH??? If you have the red lead on the positive and touch the black lead to ground it will read 12 volts. You need to go across the glow plug. You did say when you shorted the relay it started better indicating the plugs worked.

Think of the glow plugs as a light bulb. they need voltage to heatup or light up. The plug will ground itself when screwed into the head. The one wire going to the plug is the positive side of the battery the ground is the return.

When the relay is activated it provides current drawing capacity to the glow plug. Take a wire from the positive sid e of the battery tot he relay see if the relay gives you voltage to the glow plugs. The reason there is a relay is to switch the current draw fo the glow plugs if they were tied to directly to the ignition switch you would need a real big switch.