Ford Powerstroke Diesel Forum banner

96 f250 Glow Plug Relay issue

9K views 8 replies 3 participants last post by  Moterboy24 
#1 ·
Hi all, I am stumped on this glow plug relay. I am not very good with the wiring side of wrenching on stuff so hopefully someone who is can chime in. About a month ago, my GPR took a ****. So I replaced it with a Napa brand GPR. Worked great for about two weeks, then my glow plugs weren't working. I immediately thought that the Napa brand part had just taken a crap, so I ordered a nice white rodgers model that everybody reccomends. Got that, slapped it in, and still nothing. Now I know its something wiring related. With a multimeter I get 12 volts on the battery post, and 0 on everything else with the key off. With the key on, I still have 0 on everything. So it has to be something between the key being turned on, and the small post getting some juice? I don't know where to start looking. Thanks in advance gents!
 
#2 ·
One of the relay's big posts (measured to ground) should have 12V on it at all times (truck just sitting there, key off). If it doesn't you need to check the big Black wire with Orange stripe all the way back towards the batteries. There are fusible links in there and if they opened up you would get no voltage. Cheers!
 
#3 ·
Thank you for the reply Patrick. Yes, I do have 12 volts at the big post with the black and orange striped wire. My problem is when I turn the key on, I am not getting the 8 (I think) volts at the small post to actuate the relay. It looks like that power wire is controlled by the ignition switch? Sorry if the description is patchy, typing on a smart phone.
 
#4 ·
I'm fairly certain that two of the terminals should be "hot" all the time (+12v, give or take). The small terminal that's not hot should be grounded to close the relay, and the other large terminal should be showing ~11.5v or so with the relay closed (or more).

There shouldn't be 8v anywhere.
 
#5 ·
For the small wires, you should get 12V at the small Red with Light Green stripe's wire post end (disconnect the wire from the relay) with the key on Start or Run. If not, check underhood fuse #22 (test it with a meter, don't just look at it). Many times this fuse blows because the fuel heater (inside the fuel filter bowl) shorts out. You should also not get the Wait-to-Start lighting up if the fuse has blown. If it has blown, unplug the fuel heater (3 wires on the driver's side of the filter bowl ... it will be the middle one. Top is the Fuel Restriction Sensor and the bottom is the Water-In-Fuel sensor). The funky-looking spade connector comes off straight out from the side of the bowl.

For the other small wire (Purple wire with Orange stripe), disconnect it and see if you get continuity with ground when the key is placed in Start or Run. The Powertrain Control Module provides this ground to activate the relay.

Cheers!
 
#6 ·
OK... The small red wire is where I'm lacking getting any juice. I checked the fuse (#22) first and its getting juice with the key on (I used a test light at the time so I do not know any numbers) and my wait to start light comes on. But still no power at the relay end of the small wire. So I guess that means I have a break somewhere in the small red wire?
 
#7 ·
Make sure the key is in START or RUN when you check the wire. If there is still no voltage (and UH fuse #22 is verified good and passing voltage) then you will need to trace it from the relay back to the UH fusebox. Cheers!
 
#9 ·
Update. Everything is fixed. The small power wire rubbed in half on the k&n cold air intake box... Weatherproof splice and some electrical tape and were good to go! Thanks again.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top