Preheating system not working

Hello!
My Golf 3 TDI (1Z engine) has a faulty glow plug system. None of the glow plugs are working. I disconnected the glow plug connector and installed old glow plugs, but there's no power reaching them. There's also no power at the large, round plastic connector that needs to be rotated to open it, specifically at the two red wires. I checked the fuse strip, and it hasn't blown. There is power there. I also replaced the glow plug relay, but that didn't fix it either. What else could it be? Are there any other fuses? Or could there be a broken wire somewhere? It's really frustrating trying to figure this out.
Thanks in advance for your tips!

Regards,
Thomas.

Hello,
Electricity doesn't 'exist' in the sense of being present; it can only flow. And that's just something he doesn't do, especially if all the glow plugs are broken, or have you measured the voltage?

@ gaspedaluser

As far as I understand, the glow plugs are connected in parallel, not in series.
operated. It would be bad if all the candles were to go out because of a single defective one.
would no longer glow.

Hello!
'I found the problem. It was the 50A fuse in the fuse box. My great repair manual didn't mention this fuse at all. It stated that the fuse in the engine compartment was responsible for the glow plugs. However, that's not correct. That fuse is for the three glow plugs in the cooling circuit. The fuse for the glow plugs on the cylinder head is actually this larger fuse in the fuse box. But if nothing mentions this fuse anywhere, it's hard to find. Anyway, I put in a new fuse, and now everything is working again!'

Regards,
Thomas.

Thomas76 wrote:

Hello! I found the error. It was due to the 50A fuse that is in the fuse box. Well, I put in a new fuse, and now everything is okay again!

Hi Thomas,

Okay, so far so good, but what was wrong with the old fuse?

Burned out? Something like this usually doesn't happen without a reason --> could it be a hidden short circuit or a loose connection?

By the way, my tractor comes with an 80A glow plug fuse installed from the factory.
Perhaps the 50s are just slightly undersized .

Hello Ulf!
Yes, it was blown. Of course, I don't know if there's a hidden short circuit. I've never had to replace this fuse before. This is the first time. Do you think I should maybe just put in an 80A fuse directly? Would that be better?

Regards,
Thomas.

Thomas76 wrote:

Should I maybe just put in an 80A fuse directly? Would that be better?

Hi Thomas,

No idea, it probably also depends on the spark plugs.

If our cars were supposed to use the same spark plugs (who knows for sure?), I would try the 80s.

ulf wrote:

Burned out? Something like this doesn't usually happen without a reason --> hidden short circuit or intermittent contact?

Hi Ulf,

Don't you think that, for example, cracks caused by "decomposition phenomena" could eventually cause the blown fuse to smoke (due to a higher current flow per cross-sectional area) ? In my old TD, the fuse also eventually started smoking (-> a short circuit is almost ruled out). I then replaced it with a copper fuse that I made myself.

Best regards, Christian.

@haehnlein

Are you serious right now? Have fun when the device catches fire because homemade copper wire can allow incredibly high currents to flow, especially if something is actually defective!

@marco

Whether connected in parallel or in series, current will not flow if any of the glow plugs are faulty. There are experts who want to measure the voltage, but they set the measuring device to measure current (Amps) and then wonder why nothing happens.
It sounded like that was the case in this instance.

Best regards.

haehnlein wrote:

Don't you think that, for example, cracks caused by "decaying phenomena" could eventually cause the tripped fuse to smoke (due to a higher current flow per cross-sectional area)

Hi Christian,

Sure, that's definitely possible. But then, the problem should, in my opinion, occur more frequently as a "design flaw."

Quote:

On my old TD, the fuse also blew out (->short circuit is almost ruled out) at some point......I then replaced it with a copper fuse, a homemade one.

Bravely, bravely (see posting by gaspedaluser), as long as one has no reference values for which CU cross-section can handle how much current before burning out .

Best regards,

ulf wrote:

Quote: On my old TD, the fuse also blew out at some point (->short circuit is almost ruled out).......I then replaced it with a copper fuse that I made myself. Bravely, bravely (see posting by gaspedaluser), as long as one has no reference values for which CU cross-section can handle how much current before burning out

.

Hi Ulf,

should not be a recommendation I was just too lazy to drive to VW back then.

Best regards, Christian.

Temporarily, it often works to wrap a piece of aluminum foil around the fuse .