I was thinking about doing the led light mod to be able to monitor my glow plugs. Got to thinking where to put one then had a idea. Why not just tap into the dash wiring and use the squigley line that is already there. Any thoughts?

 

Main question that I can think of: Can that "squiggly line" in the instrument cluster handle the 12volts directly? I would bet that the IDM or ECU is only passing a significantly smaller signal voltage to that "squiggly line" to turn in on as needed. If you try to run it directly, you'll likely fry not just that indicator, but the entire cluster.

 

Good point. I will have to check the voltage and reduce it if needed.

 

If you had a 99-01 it would work just fine. There's a dedicated wire to the instrument panel cluster.

However, with a 2003, there isn't a dedicated wire for the glow plug indicator as the data is transferred through the data bus.

 

The PCM supplies a ground for the older trucks while 12v is always present at the other side of the bulb. No worries about voltage.

 

I'm curious as well, I have an E99 truck, do we have any good pictures of this mod/wire?? And where its location is?

 

I got a 03 so a little more work would be involved. But anything is possible right.

 

I just came up with this idea so pictures are probably not available yet.

 

well I guess its time we start looking at our wiring diagrams!!

 

i just mounted a 12 volt LED bulb in my triple gauge pod between the boost and pyrometer.
you definitely know when the glow plugs have power!!!

 

i installed a volt gauge and can monitor the glow plugs that way also. i notice my glow plugs stay on longer after the light in the dash goes off.

 

Our factory dash indicator light only illuminates for no more than 15 sec. No matter what the temp.

Do the 12v Led light mode and see that they get hot for up to 2 mins. The led is wired to the gpr relay to show when the glow plugs turn off. Then crank the truck

 

correct, the dash light only comes on for around 15 seconds whether the glow plugs relay is working or not.
by putting an LED to the output of the glow plug relay, you will see when they are getting power, which can be upwards of 2 minutes when it is really cold out.

 

I was aware that the "squiggly line" is not a true indicator of when the glow plugs were on. I wanted to rewire it to make it tell the truth instead of adding a led indicator.

 

That's not going to happen without one of a couple things:

The first (and hardest option) is running a dedicated wire from the glow plug relay to the gauge cluster, disassembling the cluster, and doing some desoldering/soldering on the cluster to disconnect the factory traces on the circuit board and adding your own. Then you have added extra wiring strewn about the cab though too. Keep in mind (and I'm not sure since I don't have an 02 cluster) but the cluster module may constantly set a code afterward about an open in the glow plug lamp circuit. This isn't a big deal to you or anybody else, but a later owner may spend a lot of money chasing his or her tail at a shop and spending lots of money to "fix" the problem.


The glow plug light "length of burn" can be changed in the tuning very easily to match what the glow plug relay command is. That's the easy way.




The main thing to remember is that the light is technically a "wait to start" lamp. When you sell the vehicle, the next owner is going to wait up to two minutes at times to try to start the vehicle unless he/she is made aware of it and some people will walk away from a purchase if there's added junk that doesn't add any value or if it adds inconvenience or more thinking just to operate it.

On the other hand, the 99-01 vehicles already have the wiring run outside the firewall. All one needs to do there is cut and splice a length of wire from the glow plug relay, use a relay from it to control a ground, then connect it to the wire for the glow plug light coming out of the PCM .