How many hours does it takes to replace a heater coil in a 2004 suburban

Why did you buy three batteries? You can charge up batteries with an $19 battery charger.

You have so many electrical issues, probably all caused by the dash cam or something damaged when the headliner was replaced. You need a good auto-electrician.

There is a blower motor control processor for the back blower - it takes input from the front control and the rear control and decides the fan speed. That processor could be faulty, or the blower motor, or a 30amp fuse in the engine compartment.
In the front system you have a controller and blend doors that direct air thru the heater core and evaporator. You would need to check the operation of those blend doors.

either rip the whole dash out, or take it to a shop that will.

the alldata book time calls for 8.2 hours labor and prices vary on the heater core depending where you live

AFTER YOUR TRUCK IS AT OPERATING TEMP CHECK BOTH OF THE HEATER HOSES GOING INTO THE REAR HEATER AND SEE IF ONE IS HOT AND THE OTHER ONE IS COLD. IF THEY ARE AS I MENTIONED THEN YOUR PROBLEM COULD BE THE REAR HEATER CONTROL VALVE (if the valve is located after where you checked the hoses) OR YOU HAVE A PLUGGED HEATER CORE AND IT NEEDS TO BE FLUSHED OR REPLACED. IF BOTH HOSES ARE COLD THEN CHECK WHERE THE REAR HEATER CONTROL VALVE IS LOCATED AND IF IT IS BEFORE THE REAR HEATER HOSES START THEN SEE IF THE HOSE GOING INTO THE REAR HEATER CONTROL VALVE IS HOT GOING IN AND COLD GOING OUT AND IF IT IS REPLACE THE VALVE AND THAT WILL FIX YOUR REAR HEATING PROBLEMS ! GOOD LUCK ! MICHAEL...

start with testing your module and coil.

sounds like a heater/ac door is not working.take apart black air box under dash but only after checking lines and wires making sure that side is not worn threw on something.

Replace! The repair cost is probably more than replacing it with a decent JVC, Pioneer or Clarion unit - and you can get a DVD player as well to keep the kids occupied ;-)

With coolant full and engine hot,make sure both heater hoses are hot. If not replace thermostat. If they are, check the blend door for proper operation. Otherwise you may have a bad climate control module. Check both front & rear units.

did u replace the fan motor.try to tap on the fan motor see if it comes on.