Glow plugs blow fuse

delicanter

delicanter

Member
So my mechanic told me my glow plugs are all dandy but their relay or timing or whatever gets them running when I turn the key isn’t working well. His solution was to install a momentary switch on the steering wheel which probably just turns on the glow plugs.

He put in this sort of double fuse where one wire from it goes to the momentary switch and from there probably to the glow plugs. The second wire goes to an EGT gauge to power it continuously.

Problem is that when I try to activate the glow plugs it almost consistently blows out one of the fuses on this double-fuse contraption. This renders the EGT gauge inactive as well.

Is this an electrical wiring problem? A weird fuse setup problem? A glow plug problem?

This is leading to me constantly losing my entire battery charge trying to start the car with no glow plugs.

In the photo: the double fuse thing.
 

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Which fuse is blowing? The 20A fuse should be what was in the slot before the fuse tap was added. And it is possible that the added circuitry on the 10A line is overloading it... i.e. the total load on that 20A fuse is potentially 30A.

If it is the 10A then the added circuits are too much for it. Assuming the momentary switch is triggering the OEM relay then 10A should be more than enough. If it is trying to directly energize the GP's then it is woefully inadequate (and doing it that way is a bad idea anyway).

Of course it could be bad wiring, or the relay could be bad... hard to say.
 
Yes it’s the 10A fuse that’s blowing off.

Should I simply search for another auxiliary fuse connection and separate the two devices?

If I disconnect the gauges and their fuse I should be able to test if the glow plugs circuit works right?
 
delicanter said:
Yes it’s the 10A fuse that’s blowing off.

Should I simply search for another auxiliary fuse connection and separate the two devices?

If I disconnect the gauges and their fuse I should be able to test if the glow plugs circuit works right?
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I can't imagine 10A is insufficient to power an EGT gauge and trigger the GP relay; the relay requires ≤ 4A. I would check how the momentary switch is wired and make sure there isn't a short in the wire from the switch anywhere (e.g. insulation cut).
 
Thanks will do.

Is it ok to disconnect the EGT gauge, cut out the momentary switch and test the glow plugs by putting in the fuse and then pulling it out (as an alternative to a button)?

What would be my indication that the glow plugs have done their job? am I supposed to hear their relay? do they turn off automatically after hitting a given temperature?

Thanks
 
delicanter said:
Thanks will do.

Is it ok to disconnect the EGT gauge, cut out the momentary switch and test the glow plugs by putting in the fuse and then pulling it out (as an alternative to a button)?

What would be my indication that the glow plugs have done their job? am I supposed to hear their relay? do they turn off automatically after hitting a given temperature?

Thanks
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Yes to all.
If the engine starts more easily then the glow plugs have had an effect.
 
The glow plugs will NOT turn off automatically with a bypass switch. Don’t leave the fuse in for more than 10 seconds or you can burn out the plugs (I believe)…

The bypass bypasses the controller that automatically turns the plugs on and off.
 
deskinthewoods said:
The glow plugs will NOT turn off automatically with a bypass switch. Don’t leave the fuse in for more than 10 seconds or you can burn out the plugs (I believe)…

The bypass bypasses the controller that automatically turns the plugs on and off.
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Good catch!

If they are ceramic glow plugs they probably won't burn out. If they are self regulating glow plugs they probably won't unless hit with excessive voltage (i.e. are on after starting). If they are cheap glow plugs they will blow out and spray/dump ceramic powder into your engine :oops: .
 
Ok here are the results of the test:

  • I cut out the momentary switch, tested it with a multimeter and it has continuity when pushed down
  • I took the momentary switch wire that went towards the glow plugs and connected it directly to power (via that sort of expandable fuse thing). I immediately heard a click, and another click a few seconds later.
  • The Delica started immediately, stark difference from preivously when Glow plugs were not engaged

@deskinthewoods - Seems like the plugs are still shutting off despite the bypass switch. Is it possible the person who installed this bypass switch didn't really install it as a bypass but just in-line? I'm not sure why they would do that but that's what I observe.

So now I'm trying to figure out why, when that same fuse also sends power to the EGT gauge and hitting the momentary switch the 10A fuse blows out. I noticed that there's another similar 20+10 fuse extension thingy that sends power to the EGT gauge. I didn't open up the EGT gauge to see how its wired but from looking at the install instructions (Glowshift 3-in-1) it seems to receive two power wires, one red and one white. The Red is expected to be constant 12V and the white is supposed to be ignition switched 12V. The 10A fuse blows out on the white cable.

Btw the white wire goes to fuse location #16 (Fifth from the right on the bottom row) and the red wire goes to fuse location #10 (rightmost on the top row). Per the diagram I found online #10 is "Door lock" and #16 is "Heater". Is it possible those just aren't rated for 30A?
 
If the controller is still functioning then I would guess, yes, the momentary switch is bypassing the ignition switch, not the controller. I’ve never heard of that before.
 
That actually makes sense, instead of tapping into an ignition switch/power.

I’m still at odds for why it would blow out the fuse though.
 
The red wire is the primary power supply, the white wire only tells it to turn on... the red wire requires 4A protection, there is no mention of required amperage for the white wire.
I would guess the white wire is damaged...
 
sk66 said:
The red wire is the primary power supply, the white wire only tells it to turn on... the red wire requires 4A protection, there is no mention of required amperage for the white wire.
I would guess the white wire is damaged...
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Do you have a sense for what part? As in the white wire that goes from the fuse to the EGT gauge?
 
delicanter said:
Do you have a sense for what part? As in the white wire that goes from the fuse to the EGT gauge?
Click to expand...
No; and thinking about it that doesn't make much sense... if there was a short it would blow the fuse regardless of the GP circuit. I would check how much amperage the gauge is pulling on the white wire. Maybe it just needs its' own circuit/fuse... but I really don't think it should,
 
Glowplugs consume 3.2A
Gauge consume 0.15A from white wire which shares fuses for Glow Plugs.

I can confirm that maybe 50% of the times I try to activate the glow plugs (with my momentary switch) I can hear the GP relay click and within 1/4 of a second the red fuse blows. I’m starting to suspect this has nothing to do with the gauge.

Could it be a faulty GP relay? Something else related to the GP?
 
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