It's wordy, but please help.
01 F350-140,000, No history of glow plug system and or battery replacment.

I've put two alternators on with in 10 months. 110 Amp alterenators from Advance Auto Parts (life time warranty). Battery discharge light goes out with each alternator replacment. Batteries seem good, starter spins over quickly and starts good.

So I started checking on the glow plug relay and the intake heater relay today. With engine running, I have battery (alternator output) voltage to BOTH GPR and IAH (Intake Air Heater) on BOTH of the small terminals on each relay and NO power output on either relay. Ok, sounds like both relays are toast...but unless someone can tell me that both of these relays are not using a ground on one of the small terminals to engergize the relay coil and that they do power feed to something else, I don't feel comfortable just replacing a these relays.

When engine is hot I do have one glow plug that shows open, although when engine is cool all glow plugs have 3-4 Ohms at valve cover connection. This one may be breaking down from heat or harness under valve cover...worry about that one later. From output of GPR terminal to harness going into valve cover all have .001-.004 Ohms on the harness. Didn't check harness resistance from IAH relay output ternimal to IAH.

Also if I'm wrong, please someone tell me, but once the glow plugs are told to cool down by PMC, after start and they cycle, that is when the IAH is suppost to kick in at that time to prevent white smoke...again, why do I have power on the IAH relay right after a cold start. IAH as I have measured it has approx. 1.0 Ohm resistance, can anyone say anything about that?

One more, I have read on here about a GPR Module. My truck is not from CA. Do I have one of these or should you just have a one or the other (GPR or GPRM)

Thanks for listening...

 

You can ohms check the harness at the valvecover. .1 to 2 ohms is a good glowplug.

 

cookie88,
Which harness, under the valve cover? I just checked from the valvecover GP pins to ground at the battery. Are you saying my 3-4 ohms for each GP is bad?? Please bear with me.

 

I'm taking this up to the "Official Glow plug" thread

 

Sorry.... was replying to a different thread.....not sure how my post ended up here, unless of course it's because I'm stupid.

Now to your questions......

Glow plug control modules are only found on Excursions and CA. emissions pick-ups. Nothing else.

With the engine warm and running both the GP and IAH relays should be off. Not sure if you have a problem there.

A good glow plug will ohms check between .1 and 2.0 ohms cold. If I read your post right it would suggest that all your GP's are bad.

 

U have to check the GPR and the ITR when the engine had time to sit over night.You have to check the bigger side of both relays,one side will always have 12 volts,even when the truck is off.Its the other side that your interested in.I beleave that the in take heater only comes on at sub zero temps,thats what a tech told me anyway.
First thing in the morning,before starting the truck,get a volt meter and see which side of the rely has no power.Then clip it to that side with no power and one temainal to the - side of the batt.Then turn your key to the on position,then check to see if you have 12 volts on the side that did not have power before.
If you do not have power on the other side,then check the small teminals to see if they have power on both side.If you do have power on both small teminals then your relay is bad.
If you dont have power on both sides then theres a senser that has gone bad.

Hope this helps.

 

The relays always have power to them. They are energized by completing the circuit to ground on the small wire by the ECU.