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No you're not. Not if you expect the glow plug circuit to function correctly, maintain a perfectly working PCM, or have the engine start at all.
They look the same, smell the same, and bolt up the same. That means they're interchangeable, right? Not even close. A bit of research this afternoon confirms that Ford's relay has no "S" or "I" terminal notation and has not for at least 6-7 years since I bought the earliest item for one of my junky pickups. Dorman's high-dollar one also doesn't have the control side terminals listed. HOWEVER, the lower-dollar Echlin ones DO. If you must buy a cheap-ish relay, make sure you check it for proper function first.
So, how do you know which one you have and how would each act in different wiring scenarios? MS Paint is my friend. The first thing to check right out of the box is the resistance between the control (small) terminals. There SHOULD BE continuity between the two small terminals and NO continuity to the backing plate or either high-current lug from either small terminal if you're looking for a genuine glow plug relay. Conversely, a starter relay will have NO CONTINUITY between the two small studs but WILL have continuity between the "S" stud and the backing plate. The "I" terminal will have continuity between itself and one of the large lugs. You don't want this one to run your glow plugs because.....well....just look at the pictures.
I noted all of your starter relay diagrams show a case ground. So if one turns the ignition key to on and measures 12 volts at both small terminals, and there is 12 volts on only one of the big lugs, it is not internally wired as a starter relay? [This sentence edited]
Thinking about the thread that apparently prompted this thread. And mindful that I went with the GPR-109 from NAPA because its was less than half the cost of the -110.
I noted all of your starter relay diagrams show a case ground. So if one turns the ignition key to on and measures 12 volts at both small terminals, and there is 12 volts on only one of the big lugs, it is not internally wired as a starter relay? [This sentence edited]
Correct...but only after the PCM control of the glow plugs times out and it's not commanding the glow plugs on.
I have, in the past (along with a friend of mine), wired the AIH and GPR in parallel to divide the current through each because short trips are hell on a glow plug relay. The AIH is a stupid idea anyway and rarely ever comes on during most usage so disconnecting the AIH relay from the heater element and having it drive one bank (yellow or brown wire) and having the actual GPR run the other bank and using a standard "Bosch-type" relay to run both the GPR and AIH relay based on the PCM's GPR output seems to work really well.
Like in the Military, just about every Tactical Vehicle has a Cold Weather Kit. I.e. M.A.C.I.'s (Military Adaptable Commercial Item) has an Antifreeze , Fuel, Oil and A/T Fluid Warmer, and Auxiliary Power Unit (APU) because they are World-Wide Deployable. Which, when in Phoenix, AZ, 120*F and 60% Humidity, you're troubleshooting a DTC for the "Climate Weather Kit" - OMG! - But, it's got to be done. And, no, it doesn't make much sense to the Technician.
But, in the Grand Scheme of things, it could well be re-deployed to the coldest rock on the Planet.
Perhaps, FoMoCo / Navistar should have only included these of Trucks for Antarctica or the South Pole
I have, in the past (along with a friend of mine), wired the AIH and GPR in parallel to divide the current through each because short trips are hell on a glow plug relay. The AIH is a stupid idea anyway and rarely ever comes on during most usage so disconnecting the AIH relay from the heater element and having it drive one bank (yellow or brown wire) and having the actual GPR run the other bank and using a standard "Bosch-type" relay to run both the GPR and AIH relay based on the PCM's GPR output seems to work really well.
I like this idea. Especially down here in the warm south! I assume starting is not a problem up in your neck of the woods in the cold?
No you're not. Not if you expect the glow plug circuit to function correctly, maintain a perfectly working PCM, or have the engine start at all.
They look the same, smell the same, and bolt up the same. That means they're interchangeable, right? Not even close. A bit of research this afternoon confirms that Ford's relay has no "S" or "I" terminal notation and has not for at least 6-7 years since I bought the earliest item for one of my junky pickups. Dorman's high-dollar one also doesn't have the control side terminals listed. HOWEVER, the lower-dollar Echlin ones DO. If you must buy a cheap-ish relay, make sure you check it for proper function first.
So, how do you know which one you have and how would each act in different wiring scenarios? MS Paint is my friend. The first thing to check right out of the box is the resistance between the control (small) terminals. There SHOULD BE continuity between the two small terminals and NO continuity to the backing plate or either high-current lug from either small terminal if you're looking for a genuine glow plug relay. Conversely, a starter relay will have NO CONTINUITY between the two small studs but WILL have continuity between the "S" stud and the backing plate. The "I" terminal will have continuity between itself and one of the large lugs. You don't want this one to run your glow plugs because.....well....just look at the pictures.
But can I use a GPR as a starter relay? From what I'm seeing I can so long as I take a wire from the other small stud to the backing plate or some other grounding point.
I didn't realize the GPR and Starter were different so I may or may not have bought a GPR to replace my starter relay...
But can I use a GPR as a starter relay? From what I'm seeing I can so long as I take a wire from the other small stud to the backing plate or some other grounding point.
I didn't realize the GPR and Starter were different so I may or may not have bought a GPR to replace my starter relay...
Yes you can. It doesn't matter which small stud is used as the exciter wire or ground, nor does it matter which large stud goes to the battery or the starter. Just know that you MUST use a dedicated ground wire on one small stud or nothing will happen.
08-03-2018, 06:03 PM
