testing glow plugs

[passat 130 tdi]

i have ordered myself a multi meter and im going to check the glow plugs , just to see if maybe they are the reason my car dont run properly , can someone tell me if a good plug has zero ohm resistance or should it have a value , do i need the ignition on when checking or leave it off ??


thanks in advance ...

[smithy602179]

i dont think you get a reading when they are duff , i just replaced all of mine from tps for 32 quid for a set of 4 .

[zollaf]

running or starting. glow plugs help with starting but once it is running they switch off so don't help.

[passat 130 tdi]

running or starting. glow plugs help with starting but once it is running they switch off so don't help.

runs as if on 2 pots only,for about 10 seconds, if i disconnect the temp sensor and it starts fine and runs fine. i just want to dismiss the glow plugs from my findings to this problem..... i know the role of a glow plug , just need advice on testing them with a multimeter.

[zollaf]

testing with a multimeter isn't always conclusive so i remove them and connect direct to a battery to observe the heating of the tip.

[S66MJETDI]

runs as if on 2 pots only,for about 10 seconds, if i disconnect the temp sensor and it starts fine and runs fine. i just want to dismiss the glow plugs from my findings to this problem..... i know the role of a glow plug , just need advice on testing them with a multimeter.

Hmmm I think you may have found your issue then! Coolant temp sensor would be my culprit. Have you run a scan, the glow plugs show up on VCDS if they are kaput.

[passat 130 tdi]

Hmmm I think you may have found your issue then! Coolant temp sensor would be my culprit. Have you run a scan, the glow plugs show up on VCDS if they are kaput.

its all listed in my " conking out on start up " thread m8 .... sensor was changed .... all i see on vcds on plugs is zeros and all 1's when they are off , is there another glow plug section within vcds i dont know about - thanks

[martin1810]

00000000 means no glow as waiting for coolant temp signal.
11111111 means glow cycle complete.

You need to watch the start up cycle to see what other values appear.
01110000 should mean ready to start.

Measuring glow plug resistance is hard because it should be just above Zero. About 1 or 2 ohms. The best method is to borrow a clamp amp meter from someone. That will show how much current each plug is pulling. Your fault does sound like a couple of glow plugs are not working. They don't only work to start the engine, they often glow a little after engine start.

[passat 130 tdi]

00000000 means no glow as waiting for coolant temp signal.
11111111 means glow cycle complete.

You need to watch the start up cycle to see what other values appear.
01110000 should mean ready to start.

Measuring glow plug resistance is hard because it should be just above Zero. About 1 or 2 ohms. The best method is to borrow a clamp amp meter from someone. That will show how much current each plug is pulling. Your fault does sound like a couple of glow plugs are not working. They don't only work to start the engine, they often glow a little after engine start.

thanks martin, finally getting somewhere , im getting 01010000 - whats this saying then ????

i will take another reading in the morning cos the temp was 49 degrees , 01010000 means no pre glow required apparently .

[passat 130 tdi]

i get 0101000 and 0.00 in the glow time box everytime hot or cold , if i set the 32768 i think it is default to 32700 it does start better and it did log a 8.6 sec glow time