03 Avalanche Electrical issues
 

hello all, I bought this truck this past august, and its had these issues since I bought it but i just haven't cared too much about them until now. First of all, both of back doors lock and unlock sporadically. Neither of them ever will lock or unlock on every attempt with the key fob or with the lock/unlock button on the front doors. But both the front doors work perfect every time. The next issue I have is with the drivers heated seat. It will come on when i turn it on, but its like as soon as it actually starts to warm up, or after about a minute it turns off. The passenger heated seat works perfectly fine. Ive taken it into a shop and had them look at it for me, and he said that everything checked out fine when checking voltage and ohms and the locking actuator in the rear doors. His next idea was something about the actual fuse box underneath the dash, but i didnt want him to tear into that because he would have had to charge me for it.
Any ideas or help would be great.

power door locks not locking or unlocking
 

Hairline crack in fuseblock, left side of dash. 03 and 04 seem to have this issue. Must replace fuse block, will correct problem. It did for me

I have the Avalanche Supreme (caddy escalade ext)
 

The exact same issue!!! I cannot believe it thank you guys so much!!
Now where to get a fuse block at a reasonable price???