92 GMC electrical problem

I was driving my 92 GMC 4x4 down a dirt road when all at once the four wheel drive went out, the speedometer stopped working and the heater stopped working
any ideas what could have caused this I am ready to try anythjing but cant figure out where all three items listed connect. Someone please help.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
dustin wrote:

Battery, battery cables, alternator.
---Bob Gross---
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
cant be battery or alternator because truck still runs starts right up headlights work and do not dim been driving it just lost four wheel drive, speedometer and heater really baffled anything else that would connect four wheel drive, speedometer, and heater?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Yeah a common grounding point between them all. Check to see if the ground strap from the engine to the chassis and the one to the cab are still OK. Bad grounds are real common. Rule of thumb on a ground is Bigger is always better. Remember all the juice used in the cab has to pass through the battery cables and through the grounds. Bad grounds gives flaky results. Also the bulkhead connector through the firewall have been known to go bad. Pull it apart and check the pins, any that are dirty or burnt? Clean or replace them.
--
Steve W.
Life is not like a box of chocolates
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.