Rare problem? no one else has this?

 

The problem seems to be the gem module. Its just an electrical device. They fail at times.
They also get wet with windshield leaks... My 99 doesn't even use the gem for the heater.
What year truck? Simple heater controls?

 

OOPS forgot to add. The truck it 2000 7.3 4wd


I wasn't sure the 2000 had the GEM module. Not having the service manual makes it difficult. I lost all this information when Katrina destroyed our home in 2005.


Does the 2000 have a GEM? or something else?


If so where would it be located?


Thanks.

 

Behind the fuse box. And yes it has one..I don't know for sure if the dealer has to program it. Some years yes some no. early No.....maybe..

 

Yes, the 2000 SD/Exc has a GEM but it is not associated with the control of the blower.

For the blower relay under the hood to receive power to be energized when the key is in the OFF position would require that there be a cross-circuit from an ALWAYS HOT power feed to that particular circuit (CJB F22). That is, the hot side of the relay coil must be shorted to battery power (the low side of the coil is connected to ground via the mode selector switch in all positions except OFF. F22 is supposed to be hot only when the ignition switch is in the RUN position.

This assumes you're only referring to the front blower, not the rear one.

 

Right the front blower only.


I have checked the diagram I do have and found nothing that connects to the blower system other than the relay and control panel switches.


There appears to be a time element on the problem. I can start and drive and the blower can be turned off / on with the ac dash panel. If I drive the truck 15 minutes and turn off with dash switches both off the blower goes off.


Now if I put the key in turn on but don't start and turn off the blower starts. I can start the truck and run it a few minutes turn it off and the blower continues. I unplug the blower and then plug it back in and it starts.


I leave the blower unplugged wait 15 min and plug in the blower doesn't run.


The problem occurs when I turn off the truck as if it were an computer / relay staying on for lighting delay then off.


I totally agree that if pin 85 and 86 have power the relay will be energized. I pulled the relay and verified the pins do have power so the relay isn't the problem.


All the wiring I have and (not the correct ones) don't show a GEM module or Vats connection.


From a power flow I understand it comes from bat / fuse / ignition switch / ac panel switch / blower relay / ground.


The blower primary coil side of the relay is where the issue is not the high amp contact side.


Is there some location after the ac panel switch and before the relay that wiring could have a pinch point. I really can't begin tearing the truck apart to pull out the harness. Being well over 65 I my back just won't let me do that.


If I knew a place to check I could check. Thanks for any help.

 

I'll look at the drawing for my 99 tonight. Should be the same...Did you try changing relay?
Any Rf radio's in the truck? water on the fuse panel...

 

I'll need to offer a correction.

In NORMAL operation, pin 85 should be HOT in RUN (it's connected to the feed of CJB F22). Pin 86 is the "low" side of the coil and must be grounded to energize the relay. It should only measure battery voltage when ALL of the following conditions are true: Ignition in RUN, mode selector in OFF, relay is inserted and the relay's coil is not defective (open). During normal blower operation, pin 86 should measure 0 volts or ground.

Pin 30 of the relay should be ALWAYS HOT via PDB F23. When the relay energizes, pin 30 is connected to pin 87 which is connected to the high side of the blower motor.

I did locate a 1999 Super Duty schematic online which should be the same for your 2000 Exc for this troubleshooting exercise.

There is nothing in the circuit that is *supposed* to include a time element, it's all pretty simple and straight forward. Now, we do realize that the system is not behaving as it's supposed to, but we do need to be clear on how it was designed to work so that we can better analyze the malfunction.




Several questions:
1. Does the blower eventually disengage after a specific interval after the ignition switch is turned off?
2. Have you tried pulling CJB F22 when the ignition switch is in OFF and the blower is running when it isn't expected to? Try it and see what happens, if not.
3. Does this truck have ANY aftermarket or dealer installed accessories up under the dash?
4. Can you associate the onset of this symptom with anything that might have caused it to start?

 

Wow thanks for the diagram. That's what I have been looking for.


1) yes it does seem to time out
2) No I didn't have the schematic but I'll will try it first.
3) No aftermarket. I have only the trailer plug factory.
4) About a yr ago I found the battery dead. I charged them and found the blower running. This was the first.


Pin 85 has power with Key off/ and AC both in off. But not all the times. If the truck has been driven 20 miles or so all turns of normally. If immediately after stop turn back on and off the blower will be running.


Where does the power come from at P22 in the Power junction box? Can the issue be further up stream?

 

I pulled fuse 22 blower running no change.


I began to go in sequence pulling fuses. I pulled 5 A fuse 14 in the under dash fuse box and the blower stopped. I looked this up and it is a Delayed Accessory Circuit. With the fuse out all works normally with the key on engine running, but nothing work key off. No elec door locks w/key fob, no alarm system, interior lights, power windows etc.


I dont' have schematic for this circuit but is this all controlled by the Gem module. I heard the 2000 Excursion didn't have one but I took a photo of what appears to be a GEM module attached to the back of the fuse box.


Fuse box photo taken from center of truck looking at driver door.





Could this be defective?

 

Go back and read post #35. Yes, all those functions are fed by by F14 via the battery saver relay which is controlled by the GEM.

At this point, I can only conclude that circuit # 298 (Violet/Orange) which runs between the load side of F22 and pin 85 of the blower relay is shorted to one of the feeds of the accessory delay relay which is pretty close to my initial hunch several days ago.

You mentioned that your wiring data wouldn't run under Win 7. What is your "wiring data" and which version of Win 7 are you running?

 

I am running w7 home prem. My software with wiring was for XP and the computer won't load it. I ordered new software for w7 hopefully it will run.


Yesterday with blower running I pulled fuse 22 and the blower kept running. I pulled 5 A fuse 14 to GEM module and blower stopped. (this reset the GEM that I know is there). I inserted the 5 A fuse to power the GEM and the blower did not blow.


I started the truck and blower functioned normally and will turn off. I shut down the truck with both a/c switches off and the blower was off before shutdown. I flipped on the blower and it started running with ignition off. I have 5 relays in the panel with #5 as acc but no description. I pulled #5 relay with blower running and it stopped.


Now I am wondering.


1) does the GEM control blower on the Limited Excursion
2) do I have a defective relay 1 thru 5
3) Is the Gem defective, I hope not apparently there are none available for the 7.3 Excursion 4wd

 

1. No. The GEM isn't supposed to control the blower on ANY Excursion or Super Duty.
2. I don't see any way that a defective relay in the CJB can cause this symptom. The Battery Saver Relay is supposed to remain energized for 30-45 minutes after ignition shut-down. The Acc'y Delay Relay is supposed to stay energized after ignition shut down until the GEM detects a door has been opened. Neither relay is supposed to have any connection to the climate control blower system.
3. I see no evidence of a defective GEM based on data so far. I'd suspect it's either the CJB or a wiring harness fault.

See pages 140-142 inclusive in owner's manual.

This computer that I'm using this morning is running W7 home premium also. I had to install VMware, then install Win XP inside VMware. My Ford service CDs and DVD all run inside the virtual machine as virtual disks.

 

I have the owners manual and know the purpose of the relays but the point to point wiring is what I am missing by not having the manuals. What is VMware? is it a public down load or program.


JST an fyi,, I am well over 65 and pulling out dash wiring is a bit beyond my physical ability now. 20 yrs ago I would have the wires in hand.


I need to get the point to point and understand where the wires go under the hood before I do any work. My back won't let me bend after so many years of pulling wrenches.


My thoughts are power is getting to the + side of the relay coil as you covered. I just don't know any of the where to's of that wire or in dash routing.

 

Edit [Had wrong application and URL, corrected ]: VMware Player is free. You'd still need to install XP inside it so you'd need valid XP install media with product key.

https://my.vmware.com/web/vmware/downloads Scroll down to bottom of list. If you have Win 7 Pro or Ultimate, it's supposed to run the old stuff but I haven't tried it.

I hear you about getting under the dash. I got two new knees about a year and a half ago and I just don't bend like I used to.

Let me see if I can put together a package of schematics and the associated locators. Might be today, might not be until Sunday, though.