Hi everyone.

1998 Ford Expedition (same as f150 for all appplicable parts)

I have scoured the internet and forums but have not been able to find my specific problem (and it is rather specific).

my windows, wipers, done lights and 4wd started working intermittently. During this period they would come back if I bashed the underside of the dash a couple times. Also during this period the speedometer and blinkers went intermittent.

I decided to try and fix it proper and got a new gem. The old gem and fuse box look perfect. There is no corrosion, water signs etc.

now with my new gem or old gem windows, dome, wipers and 4wd all don’t work and hitting under the dash does not bring it back. The speedometer and blinkers are now working fine again.

I think it must be a bad ground, bad wire or something like this, but I have no clue where to look to find this bad wire.

any help would be immensely appreciated, I am happy to provide more information.

 

odd question, has it rained recently where you live? Or do you frequent drive through car washes?

 

No water damage (I have had the gem out and took a really close look at it).

I am familiar with the water damage issue that I have heard a lot of people have problems with and there was no sign of corrosion or water damage. The board looked immaculate.

I think it’s a bad ground, not receiving power or something similar To this but I’m not sure how to diagnose it.

thanks for your reply!

 

I'm sure I'm going to catch hell for this again but you can't. The auto makers only offer up point grounds which is a black dot with 3 lines below it in a triangular shape. That tells you where in a circuit but not what. The symbol for chassis ground looks like a skewed rake. There's also a symbol which is an upside down triangle that can be solid or hollow. Solid simply represents a signal ground. Usually hollow if inside there's an A or D or 1 or 2. This identifies an analog or digital signal. There's also earth ground which doesn't exist in a vehicle. Also what isn't identified are the reactor grounds which is what is used in a welding machine to prevent getting electrocuted. Electrocution isn't as much of an issue with a vehicle. Their more for preventing ground loops and noise. There are other reasons that go way beyond what I understand. The auto makers also don't identify secondary circuits. Modules are primarily secondary circuits which allows for all the circuits to run on a different voltage and current. A short explanation is they prevent the tendency of electricity to balance itself. The manufacturers don't offer up anything beyond the ubiquitous chassis ground with a point ground and maybe the battery and charging system case ground. That's what you're limited to unless you bring the necessary knowledge to go farther on your own.

EDIT: the signal ground has the 3 lines also

 

That’s interesting information. So I guess there aren’t any diagrams that explain the gem modules wiring?


are there any other issues that you suggest?

Thanks for your help!

 

LOL

The circuits are identified by pins and wire number and color but you get nothing about what's in the module. You can cheat it all with chassis ground but that doesn't mean you're actually fixing anything. It's just offering up an alternative but that actually can have it's own problems like noise and loops. Chase the grounds down and see where you've kept the current but used the voltage. That's about all you get.

 

Okay I see what your saying now.

where can I find the pin out for the gem?

thanks!

 

Just a thought but if you have tilt steering wheel, try putting it always up. I have run in to wires pulling lose from the connector on the ignition switch.

 

Someone here may have it for you but I'm sure you can find it online.

 

gave this a try today. Really crossed my fingers for it too! But this unfortunately didn’t change anything.

i haven’t been able to find a wiring diagram for the gem unfortunately.

haven’t found the issue but still trying