I pulled glowplug 1 and I think it is the original 7v ceramic. It is a bosch and comes to a point (not flat at the tip) someone on this forum stated the ceramic ones were flat. Any conformation of this? Anyways, when i measured voltage to the plugs during a key cycle, I get 9v for a split second, then it levels out at about 5v for the remaining 5-10 seconds. My question is: should I be getting 7 volts steady for 7 volt glowplugs, or has the computer been reflashed to 5 volts and the plugs never replaced with 5v plugs?

Looking at my old ceramic plugs, the tips are tapered and rounded.
And its hard to see but it does say bosch 7.0v on the shaft.

Its hard to read GP voltage due to the pulse width modulation of the circuit.
If your plugs are 7 volt then you likely have 7 volt programming.

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U.S. Army Retired

do you see any problem with dropping in the bosch 5v plugs with out the reflash?

The only problem I can see is that the 5v glow plugs might burn out quicker when used on 7v programming.
It really depends on how cold your climate is.
They might last for 1 year or maybe 3.
I really dont know for certain.

But there have been many recent posts about glow plugs and cold starting. Read through for more info.

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U.S. Army Retired

does the fact that im getting 5v primarily to a 7v plug sound within spec?

Depends on what type of meter you are using.
Most meters cant accurately read the pulsed voltage to the glow plugs.

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U.S. Army Retired

is there any other way to know if the computer has been reflashed to the 5v or still at the original 7v?

Look at the pics in this thread for a side by side comparison of a metal sheathed plug (Beru) and the Bosch ceramic viewtopic.php?f=5&t=63113 The ceramic has a small nipple like feature on the end.

Measuring PWM on a multimeter is questionable. Coupling, bandwidth and PWM frequency will all play a part so a different manufacturer/model of meter will give you a different result making it difficult to compare your findings with other owners.

One thing to note is that the voltage spec of the plugs is RMS voltage. You are probably measuring something close to average voltage with your multimeter set to DC. If this is the case, and we assume a peak voltage of around 11V available at the plug after wiring and control module losses, 5Vavg corresponds to around 7.4Vrms.

To read this voltage properly you need an oscilloscope or true RMS voltmeter but even with the latter it needs to be able to account for the DC component of the signal which not all meters are capable of.