Glow Plugs light on dashboard lighting up again after ignition

[vdimov74]

Hello everyone I'm new here and need some help please.
My Mercedes A 200 / 2005 / Diesel was showing plugs light warning and I took it to local mechanic to check it on computer he said all 4 glow plugs need replacement
and I said ok replace them. One day latter I got a call to go pickup my car and the light was still on! I asked him why the light is still on if you changed all of them.
He told me that I need to drive and the light will be gone after some time untill computer register this new parts which was really suspicious to me since I do work with computers and know that any change is instant. So please advice me is he lying to me and could it be relay in this case since I need this fixed.

Thank you everyone for taking time and reply to my post.

 

[Blobcat]

Hello and welcome

Glow plug light coming back on after starting denotes, one (or more) of the glow plugs has failed - or the glow plug control has failed.

 

[vdimov74]

Hello and welcome

Glow plug light coming back on after starting denotes, one (or more) of the glow plugs has failed - or the glow plug control has failed.

Thank you Blobcat, but if he replaced them all so it means glow plug control has failed right?
Can you please point me in right direction like where it's located and how to check it's faulty or would the computer check show the error codes for glow plug control?
Thank you for taking time to reply.

 

[EmilysDad]

.....
He told me that I need to drive and the light will be gone after some time untill computer register this new parts which was really suspicious to me since I do work with computers and know that any change is instant. So please advice me is he lying to me and could it be relay in this case since I need this fixed.

Thank you everyone for taking time and reply to my post.

he's taking the proverbial

 

[mioba]

your mechanic is a cowboy
Plugs or relay make the light come on.
Did the mechanic use a scanner or guess.

 

[curious]

He simply hasn't fixed the fault.
You should give him a chance to put it right, at no extra cost.
If he doesn't or doesn't want to, you can take it elsewhere and then bill him for the costs involved.
You can aslo claim reasonable losses and expenses but generally not inconvenience or your time.

Did you pay by credit card?

 

[vdimov74]

your mechanic is a cowboy
Plugs or relay make the light come on.
Did the mechanic use a scanner or guess.

Yes indeed it look like he is, he did use scanner and it was showing plugs need changing and he said he changed them, thats why I told him it's relay if you changed the glow plugs and he said if it's relay I will change it for free because scanner showed plugs. I'm going to visit him in the morning and be there this time to see what he's doing.

 

[vdimov74]

He simply hasn't fixed the fault.
You should give him a chance to put it right, at no extra cost.
If he doesn't or doesn't want to, you can take it elsewhere and then bill him for the costs involved.
You can aslo claim reasonable losses and expenses but generally not inconvenience or your time.

Did you pay by credit card?

He said he will replace the relay if the plugs are not the issue since i mentioned him it's the relay if you changed the plugs, so will see this in the morning I'm going to visit him. I paid by cash but all I need it fixed nothing more. Thank you for taking time to reply. Cheers

 

[sonic]

I can't believe he changed the glow plugs & tried to give you the car back with the light still on.
Hopefully the relay change will solve the problem.

 

[Blobcat]

I can't believe he changed the glow plugs & tried to give you the car back with the light still on.
Hopefully the relay change will solve the problem.

Hopefully they did change all 4 and not just the ones that came out easily… and that they didn’t break any…
I know I’m thinking the worse

 

[vdimov74]

Yeah thats what made me suspicious in the first place, but let's see tomorrow I will be there when they put the scaner on and see what it will show.

 

[vdimov74]

Hopefully they did change all 4 and not just the ones that came out easily… and that they didn’t break any…
I know I’m thinking the worse

You're not thinking the worse that's exactly what I'm thinking since he said he changed all 4 and I did pay for all 4.

 

[curious]

Hopefully they did change all 4 and not just the ones that came out easily… and that they didn’t break any…
I know I’m thinking the worse

Removal of glow plugs from this engine needs to be done with knowledge or experience. (I learnt the hard way after snapping the first one off.)

 

[EmilysDad]

Many years ago I had No 5 glow plug on my R Class diagnosed as u/s by a local indie .... it'd gone there for something else. At the time he said that even though their diag kit had said it was a particular glow plug that had failed, it could be the relay. I changed the GP myself, & needless to say it didn't fix the fault. A new relay sorted it.
That's not to excuse the OP's local mech for sending the car out with the GP light still on & telling a tall tale about the computer registering new parts etc

 

[vdimov74]

Hey everyone here is an update: I did not get a call so I decided to go there and see what is going on.
After waiting some time since he was trying to avoid me I finnaly asked him is it done and his reply was same I changed the relay it will take some time to be registered by computer and I tried same MIL was on. So I asked him did you even connect it to scanner and he said no and I was like why did you charge me then for glow plugs if you did not connect it first. So I requested full refund and I took my scanner and connected it, it was showing U0106 Lost communication with glow plug control module (GPCM) and he was like let me check the fuse but that was not it. I can see he does not have clue what the issue is, Could it be the module that he put some used one or something else. My scanner was showing only that error nothing more. Please if you can advice me what to do further I'm getting my refund in the morning and I don't want to go to another clueless mechanic without being prepared to what may be the issue here. If it's GPCM I'm sure I can change it by myself. Thanks everyone once again.

 

[curious]

Given you're now where you are with this, I would go to one of the independents that get recommended on this forum.
Whereabouts in the country are you (assuming UK)?

 

[vdimov74]

Given you're now where you are with this, I would go to one of the independents that get recommended on this forum.
Whereabouts in the country are you (assuming UK)?

I'm in Milton Keynes, but ordered GPCM module from ebay replaced it and issue is gone. Thank you for your effort and sorry for late reply.

 

[Botus]

Thank you Blobcat, but if he replaced them all so it means glow plug control has failed right?
Can you please point me in right direction like where it's located and how to check it's faulty or would the computer check show the error codes for glow plug control?
Thank you for taking time to reply.

if you look on ebay for BMW stuff (which uses mostly the same nasty quality rubbish) - most people sell glow plugs and the control box as 'a service kit'

there is no reason not to do this on a Merc - parts and technology evolve - if you get hold of a new control box (we incorrectly call a relay) this ECU has hardware and software control updates - which may (should) relate to improvements in the glow plugs

its been more than 15 years since they are NOT just start up helpers - glow plugs on recent era cars switch in and out all the time - to tidy combustion and for emission control

beru makes lots of these parts and like everything they can die - one of the six new ones in my father's car gave up in 6 months and 2k miles - its replacement and all others still OK 20k miles on

 

[Hardaker]

I may be a bit behind on this. Glow plugs are simple devices (resistors) but you might need a special pair of pliers to get the lead off. One will be open circuit and you can find that with a meter. Leave the lead off (as it does nothing anyway) and remove the glow plug with the engine warm. Use some decent spray with Teflon or PTFE in it. Insert new plug (I get mine on eBay) and torque up. Refit lead. Light should now be OK. However, it will not be long before it is back on - a few months maybe - so make life easy and change the lot at the same time.
If all glow plugs are OK it must be something else.
I did my 'training' on a W220.

 

[vdimov74]

I may be a bit behind on this. Glow plugs are simple devices (resistors) but you might need a special pair of pliers to get the lead off. One will be open circuit and you can find that with a meter. Leave the lead off (as it does nothing anyway) and remove the glow plug with the engine warm. Use some decent spray with Teflon or PTFE in it. Insert new plug (I get mine on eBay) and torque up. Refit lead. Light should now be OK. However, it will not be long before it is back on - a few months maybe - so make life easy and change the lot at the same time.
If all glow plugs are OK it must be something else.
I did my 'training' on a W220.

Thank you for the reply, it was glow plug module got it on ebay the light went off when I changed it.