The Mégane II Owners' Club

Read the fault codes through EOBD connector. They will show what causes the light. ELM327/ELM323 from ebay are known to work. A friendly garage can do it for free...

Multiple refitting the glow plugs increases the risk of damaging the thread in the aluminium block. Some people sometimes manage to brake a plug, thus causing expensive repairs. Be warned.

yes that will read your fault codes just connect it up to a laptop if you want the software for it you can get it for free if you know where to look

if you don't know where to look pm me and i will email it to you

save yourself £10 and get this one instead its exactly the same http://cgi.ebay.co.uk/OBD2-ELM327-V1-3-OBD-II-BARGAIN-L-K_W0QQitemZ150342615726QQcmdZViewItemQQptZUK_Diagnostic_Tools_Equipment?hash=item150342615726&_trksid=p3286.c0.m14&_trkparms=72:1689|66:2|65:12|39:1|240:1318|301:1|293:1|294:50

There's only one way to test if your heater plugs are working or not:

Remove each plug in turn;
Get a battery & a set of jump leads;
Connect one end of the Neg lead to the Neg Batt post and the other to the threaded part of the heater plug (the part that screws into the block);
Connect one end of the Pos lead to the Pos Batt post and with the other touch the terminal on the heater plug where the wire normally connects.
There will be a small spark nothing to worry about. After a few seconds the plug part should start to glow red if its ok. If it stays cool then its knackered.
Repeat with the other 3.

Very crude diagram:

freddymercurystwin wrote:Okay well I chose that one because (I detest ebay btw) that seller has better feedback, seems to have faster postage and only sells fault readers rather than allsorts. Anyhoo as they're both the same, presumably I get aome basic software with it and once loaded onto my laptop lets me read the fault codes and tells me what they are, what does the software thats not included give me?

With the free software you will probably find that some features are locked and are only available on the full versions. However if you *AHEM* look in the right places you will find what you are looking for.

Plugs either work or they dont. All they are is a coil of wire that heats up when current is passed through, and eventually they burn out. If its intermittant then i would say the fault is somewhere else in the cold start circuit rather than the plugs themselves. The above method is the only way to be 100% sure the plugs are working or not and is worth a try before you spunk £40 on a new set.

freddymercurystwin wrote:

busternlouie wrote:The above method is the only way to be 100% sure the plugs are working or not

But a meter cannot lie? Or can it?

Yes.

Enjoy!
https://www.obddiag.net/allpro.html

freddymercurystwin wrote:

busternlouie wrote:

freddymercurystwin wrote:Okay well I chose that one because (I detest ebay btw) that seller has better feedback, seems to have faster postage and only sells fault readers rather than allsorts. Anyhoo as they're both the same, presumably I get aome basic software with it and once loaded onto my laptop lets me read the fault codes and tells me what they are, what does the software thats not included give me?

With the free software you will probably find that some features are locked and are only available on the full versions. However if you *AHEM* look in the right places you will find what you are looking for.

Well tbh I'm hopeless at locating free stuff from dubious sources but would the software that comes with reader read the codes? Maybe someone can point me in the right direction?

Your not alone, that link was completely foreign to me

Was thinking of getting a code reader thingy but that has just scared me away from the idea.

What is so foreign there? Skip the design part as your interface will arrive already assembled and tested. Everything else are screenshots illustrating the tool's functionality, the pinout of the connector for your reference only, links to the diver and the tool. Freddy's twin asked about the software -- this link contains the examples. The codes themselves are listed in many web sites, for example:
https://www.obd-codes.com/trouble_codes/

Could be a faulty preheat module or wiring to the module. Check the connectors for corrosion etc.




EDIT:
Found these on AUTODATA:


So it looks like it is the module or wiring. Check as suggested above.

freddymercurystwin,

The glow plugs are supposed to have resistance of 0.6 Ohm. This is a bit less than you measured...

AlexB wrote:freddymercurystwin,

The glow plugs are supposed to have resistance of 0.6 Ohm. This is a bit less than you measured...

Yes I noticed that too, I would still recommend pulling them all out and physically checking them if you still suspect the plugs

freddymercurystwin wrote:

busternlouie wrote:

AlexB wrote:freddymercurystwin,

The glow plugs are supposed to have resistance of 0.6 Ohm. This is a bit less than you measured...

Yes I noticed that too, I would still recommend pulling them all out and physically checking them if you still suspect the plugs

With my ammeter I get a resistance just through the wires of 0.6 so surely if I minus 0.6 off the readings I got that would make them about 0.6 in reality? My next move will to be check them all with the physical check or will replace each one with a new one for a while to try and isolate the duff. You may think I'm mad but Im not 100% convinced a glowplug cannot have an intermittant fault. As the most obvious suspects and the easist items to change in the system I may end up just replacing the lot. At least if the lights still appear following replacement of all 4 I can discount them from the equation.

Yes you are right, if the resistance of the leads alone is 0.6 ohms then if the plugs are ok the reading should be approx 1.2 ohms as you are getting.
And again you are right, the actual heater plugs cannot have an intermittant fault themselves, but they are point at which you should start when trying to diagnose a cold starting issue. Whip them all out and check them as i described earlier and if they heat up they are working no ifs or buts, then start looking further down the line ie the module / wiring.

When I had a glow plug failed, I just bought 4 new plugs from GSF ane the problem was gone. One of them had infinite resistance. In your case it might be something else. Before replacing the glow plug control module (GPCM) I suggest to check the appropriate fuse (see the circuit diagrams in Links -- they are in English). I think it is the fuse 70A under the bonnet. The next is to check the wires to the GPCM, as they may be broken inside the insulation due to strong current (pin 3 in particular). Connector pins must be also checked for corrosion and thermal damage.

AlexB wrote:...One of them had infinite resistance...

Not one of the new ones surely?