Disco 1 Glow plug relay

Steviecops · May 1, 2017

Changed glow plugs the other day but suspect they aren't doing their job. I checked the relay and it's clicking on when the ignition is switched on, but can't hear it clicking off. Batteries in my multi meter are flat so can't test voltage at the plugs until tomorrow.
Any ideas?

sierrafery · May 1, 2017

Measuring voltage with plugs connected is the only 100% relevant test

discool · May 1, 2017

Ideas? Let's wait until u have a functioning multimeter and have check the plug voltage.
Some relays are noisy on contact and can be near silent on release, could u hear the relay release before?

sierrafery · May 1, 2017

As long as it makes noise every time on ignition it means that it released before that even if in silence

brian47 · May 1, 2017

A relay can make a clunk when it's energised, but even then there's no guarantee that the contacts are making correctly.
As said by the others, the only way is to put fresh batteries in your DMM and do the tests.

discool · May 1, 2017

brian47 said:
A relay can make a clunk when it's energised, but even then there's no guarantee that the contacts are making correctly.
As said by the others, the only way is to put fresh batteries in your DMM and do the tests.

Exactly

but then on vehicle electrics I prefer my analogue meter

the fluctuation of the Fluke doesn't help for a speedy diagnosis.

Steviecops · May 1, 2017

Ok, will post results tomorrow. Thanks.

brian47 · May 2, 2017

discool said:
Exactly but then on vehicle electrics I prefer my analogue meter the fluctuation of the Fluke doesn't help for a speedy diagnosis.

I know exactly what you mean. There are many times when I prefer to reach for my trusty old AVO 8.

Spong · May 2, 2017

brian47 said:
I know exactly what you mean. There are many times when I prefer to reach for my trusty old AVO 8.

Elitist! Nothing wrong with a humble Selectest 50 - especially when it was free out of the company skip!

Steviecops · May 2, 2017

Ok, just checked with my cheapo dmm and when ignition is switched on, the voltage hovers between 11 and 13 volts, then drops away to nothing after about 5 seconds. So I guess all is working as it should?

brian47 · May 2, 2017

Steviecops said:
Ok, just checked with my cheapo dmm and when ignition is switched on, the voltage hovers between 11 and 13 volts, then drops away to nothing after about 5 seconds. So I guess all is working as it should?

That would seem to rule out the relay and the circuit driving it.
If you seriously suspect one or more of your glow plugs, you can either check the resistance of each one individually, disconnected from the rest of the circuit, you'll be looking for a low resistance value, or you can pull them and check that each one heats up when you stick 12 volts across it. DO NOT HOLD ON TO THE GLOW PLUG WHILE DOING THIS unless you have asbestos gloves! They should get very hot, very quickly.

discool · May 2, 2017

brian47 said:
That would seem to rule out the relay and the ECU circuit driving it. The ECU, by the way works out how long the glow plugs should be activated based on the measured temperature of the engine coolant ..... thought I'd just sling that in as a bit of additional information.
If you seriously suspect one or more of your glow plugs, you can either check the resistance of each one individually, disconnected from the rest of the circuit, you'll be looking for a low resistance value, or you can pull them and check that each one heats up when you stick 12 volts across it. DO NOT HOLD ON TO THE GLOW PLUG WHILE DOING THIS unless you have asbestos gloves! They should get very hot, very quickly.

Well that sounds interesting if it's true, so where's the ecu and the coolant sensor located then, as my belief is the Tdi uses just a timer relay.

sierrafery · May 2, 2017

Steviecops said:
Ok, just checked with my cheapo dmm and when ignition is switched on, the voltage hovers between 11 and 13 volts, then drops away to nothing after about 5 seconds. So I guess all is working as it should?

where did you measure this cos that's important... were the glow plugs connected when you measured?

brian47 · May 2, 2017

discool said:
Well that sounds interesting if it's true, so where's the ecu and the coolant sensor located then, as my belief is the Tdi uses just a timer relay.

Just because you seem to always want to have the last word, I've edited my post to remove any and all references to the Td5 engine. The rest of the post refers to just ordinary measuring methods which would apply to any situation of a relay switching a heating element.

discool · May 2, 2017

brian47 said:
Just because you seem to always want to have the last word, I've edited my post to remove any and all references to the Td5 engine. The rest of the post refers to just ordinary measuring methods which would apply to any situation of a relay switching a heating element.

Oh dear, so it wasn't true... wake-up

brian47 · May 2, 2017

discool said:
Oh dear, so it wasn't true... wake-up

It is on the Td5.
And I am awake! Are you? it took all of 17 minutes to reply to my retraction.

discool · May 2, 2017

brian47 said:
It is on the Td5.
And I am awake! Are you? it took all of 17 minutes to reply to my retraction.

Replying to forum posts is never my priority even if I had the time, but I don't I have better things to do such as work for a living, tonight writing risk assessments and method statements of two site meetings tomorrow.

Sent from my iPad Air on a train.

Steviecops · May 2, 2017

Glow plugs were in and measurement taken from the little nut on the top.

sierrafery · May 2, 2017

Steviecops said:
Glow plugs were in and measurement taken from the little nut on the top.

Then the plugs and theyrs circuit is ruled out as long as you can vouch for the plugs albeit 5 seconds seems too short time for me so I'd replace the tim,er relay if i was you

Steviecops · May 3, 2017

Thanks. Where is the timer relay located?

Disco 1 Glow plug relay

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