Glow plug realy getting HOT - Diesel Forum

igotrobbed · 09-23-2006, 05:26 PM

On my truck the WTS light would only stay on for about 5 seconds , and usally wont start , warm weather . I checked all the glow plugs and all were bad but 2 . I changed all of them with motocraft . I just put all new ones on last year , and have barley touched the truck , so I was reading through a 'controler' search and read that a bad ground can shorten thier life . Now the ground was described as being on the drivers side valve cover , but mine is just ground to the driver side controller boldt , and not long enough to reach anywhere else . So I threw on another wire reaching from that ground to the valve cover .

Now I'm ready to try and start it , a buddy turns the key , and I notice a small amount of smoke coming from the relay . And it gets REALLY hot , like burn to the touch . I immediatly turned off the key , tryied it a couple more times with the same result , never more than a couple seconds . I also hear no clicking at all (I cant remember if the clicking happend during the WTS light on , or after , but I havent waited for the light to go off obviously) . All glow plug wire harness ends have continuity to the correct relay post . Battery terminal reads a hair over 12v , key off .

I'm not really sure the operation of the whole system . If anyone has a link to a write-up so I can use some common sence on my own and troubleshoot it would be great too .

BTW relay is fairly new .

BuilderBob · 09-23-2006, 08:04 PM

You likely have a relay problem, that can be solved by replacement.
That is the easy explanation

Remove (disconnect)all battery cables,
Remove the GP controller
Disassemble the top relay from the controller.
Go to a good supplier(NAPA)and match the parts, replace the power relay, & re-assemble.

The heat is cause by current, and high resistance, such as a poor connection. Traditionally relay connections are copper with silver plating. Copper for conductivity & silver for corrosion resistance.
No smoke should ever appear from the connection, it is burning grease, insulation, whatever.

My GP controller will whine, actually make a noise like mouse. But it is electrically perfect.

[ QUOTE ]
so I was reading through a 'controller' search and read that a bad ground can shorten their life

[/ QUOTE ]

Not true, but it is true that this GP controller must have an excellent ground. The ground must have integrity, meaning, not frayed, damaged. I would scrub (scotchbrite) the connection (engine & ring terminal), and flush with a brake cleaner.

My controller is grounded on the back of engine, out of direct eye sight.

Go over the basics, correct any wrongs, check the GPs again for continuity, and report back.

Mr_Roboto · 09-24-2006, 09:43 AM

I think that the wire you extended was not a ground, but a power wire and you shorted the power out, hence the hot relay.

The relay is a standard Ford starter relay, and is made to handle lots of power. It shouldn't (IMO) get hot on regular GP loads.

Feel on the rearmost intake manifold bolt on the drivers' side and you should find the ground wire.

igotrobbed · 09-24-2006, 11:06 AM

OK , I just checked this whole mess out again . The wires to the glowplugs and plugs are all good . The wire I extended was a ground , which is now grounded to the correct spot . I think the ground was never a problem , because if I totally disconnect it , the WTS light wont even come on .

Battery reads 12v key off . If I turn key on it drops to 10v . Ignition and glow plug terminal then read 9-10v . Power off there is continuity between ignition termnial and glow plug terminal .I'm guessing this means a short in the relay? In any case I'm going to buy one now .Found a thread where people purchased a working relay at AZ for 9.99 .

igotrobbed · 09-24-2006, 07:48 PM

OK , it was more than than 10$ , and they will have it tomarrow . So in the mean time I pull the old realy and mess with it in the garage . Hook it upto a battery and you can hear the selinoid engage and dis-engage as it should .

Power off - open circuit .
Power on - closed circuit .

So now I'm thinking this relay is fine , hook it back upto the truck , and same original problem . Why is it that only 9-10v would be on the glowplug side and not 12v ? Any way , I started the truck , and then took a volt reading off one of the glowplug harness ends . 10v!! The relay never disengaged . . . . Is this a controller problem ? What causes the relay to disengage? I'm assuming ignition power comes from the controller?

9ENGEL · 09-24-2006, 10:36 PM

Did you run a wire from the ground terminal on the relay to valve cover ground?

I ask because the controller cycles the glow plugs by grounding the relay, so if you conected the relay ground terminal to permanent ground the relay would be engaged as long as the key is on. Which would get the relay very hot.

The ground wire to the valve cover is the black wire from the controller, the relay has no permanent ground.

Mr_Roboto · 09-25-2006, 12:18 AM

To expand on 9engals' post.

There are 2 small wires on the relay. One is positive, and is switched by the ignition switch. The other is ground (white wire), and is switched by the controller. Of course the 2 large wires are power in and power out.

igotrobbed · 09-25-2006, 05:15 AM

The white wire is the only ground on the relay , the black wire from the controller is grounded to the manifold now .

From what your telling me , the ignition terminal must always be hot once the key is on , and the circuit is opened by the controller through the common wire?

Anyway to test the controller?

Mr_Roboto · 09-25-2006, 10:02 AM

[ QUOTE ]

From what your telling me , the ignition terminal must always be hot once the key is on , and the circuit is opened by the controller through the common wire?

Anyway to test the controller?

[/ QUOTE ]

Yes, the positive is always hot when the ignition is on. It is on the same wire as the Fuel Shutoff Solenoid.

I don't think there's any way to test the controller other than by process of elimination / known good part replacement.

igotrobbed · 09-25-2006, 05:10 PM

Ok thanks for all your help . I believe the relay has a short , and the controller is shot because power is still to the glow plugs after start-up . I just bought a pushbutton starter switch which I'm going to by-pass the controller with .

I'm thinking pull the relay right off , tie the fuel shutoff wire to the ignition wire and I'll be set . Then run a wire from battery wire through the switch , to the glow plugs harness . correct?