After replacing relays, fuses, alternator, battery, vacuum lines, 4x4 motor, 4x4 actuator and everything else we could think of we tracked it down to the Generic Electronic Module (GEM) I have been hearing relays clicking and a strange hissing sounds for days now and traced it to the relay box (GEM) under the dash. When we pulled this out we found that there is a "Pickup Electronic 4x4" computer on the back of it. Both were full of water and condensation causing everything to malfunction intermittently and or constantly. The GEM controls absolutely everything needed for the truck to function correctly. I am hoping by replacing this everything will work just fine. Now I just have to find one.
In my many hours of searching and research I came upon this article via motoralldata.com:
GENERIC ELECTRONIC MODULE (GEM) - WATER
INTRUSION INTO GEM MODULE - SERVICE TIP LIGHT TRUCK:
1997 F-150, F-250 LD ISSUE
Water intrusion into the Generic Electronic Module (GEM) may occur on some vehicles. This may be due to a lack of protection of the GEM for water leaks into the cab. ACTION
When replacing the GEM, do not remove the plastic watershield that is on the new Service part. Install both items when the GEM is serviced. Refer to the appropriate 1997 F-Series Workshop Manual Section for diagnostic and installation procedures. OTHER APPLICABLE ARTICLES: 98-9-13
WARRANTY STATUS: INFORMATION ONLY
OASIS CODES: 102000, 110000, 202000, 203000, 205000, 206000
Along with a list of many things that happen when it gets "water intrusion"
This makes me both happy and mad because I spent so much money on all new parts just to find this out, but then again, I have all new parts.
If anyone has any info to where I can pick up a new or used GEM with the 4x4 module I would be very happy.
Here is some information and testing procedures for anyone with issues caused by the GEM -
I had seen your previous thread about the issue you were having. I am sorry you are having issues but it sounds like you have the answer now. I, like others on this site, appreciate the information. I like to read about problems other have had and what they did to remedy them. Sites like this have always saved me a ton of cash.