I am a new user to the site and hope someone can help me with a major issue with my 2006 g35X sedan, 98K miles.
I have no heat in my car. I purchased the car in the spring and did not notice this problem at that time. Cold air from ALL vents when idle. Periodically, warm AIR blows ONLY from the drivers side vents when driving - and this is not consistent. I've had a mechanic check this problem and without spending more money or effort, I would appreciate some input from experts on this forum. He is what has been done so far:
1. Radiator flushed and burped to remove air and bleeder screw adjusted. This makes HOT air (HEAT) comes only from the drivers side vents when maintaining the RPM @ ~2, but when idling, no HEAT. All other vents continue to blow COLD air, even when RPM at ~2. Yes, both dual controls are set to 90 degrees, the max.
2. Changed the thermostat with an OEM part. No luck.
3. Checked all fuses. No issues.
4. Checked and even replaced one of the actuators - blend door motors. They are work fine. Replaced the climate control blend door motor to see if it made difference, and it did not.
5. I have been told that the only option is the HEATER CORE and that should be replaced. But I don't understand because it does not seem to be clogged. We flushed several times (reverse pressure in the in/out hoses, with limited debris coming out), and the driver side vents give out heat when we burp the system more and more, but not any of the other vents, they continue to blow cold air.
6. The blower motor blows strongly, no issue.

Could it be an electrical issue?

HELP PLEASE!!

 

Sounds like you still have air in the system, these things are a pain to burp and most folks recommend a procedure that involves a Lisle spill free funnel and something along the lines of.

(Entire procedure performed with windows down and AC system on MANUAL (not auto) max heat, max fan speed)
-Manually purge air via bleed screw

then

-Jack the front, run till hot while manually squeezing the supply/return radiator hoses by hand.
-Drive the vehicle at medium to high rpm for a few blocks.
-Let engine cool, Lisle spill free funnel and radiator hose massage until hot again.
-Drive the vehicle at highway speed, aggressive acceleration to achieve speed.

Rinse/repeat until you have hot air

What sounds to me is that you have the AC compressor cycling on which is overpowering the limited amount of hot air you would normally get from the other vents making them blow cold. Don't rely on the system to suck water from the reservoir, the spill free funnel allows you to add directly to the radiator since the reservoir doesn't actually FEED liquid to the system during normal operation and the cap (or spill free funnel) needs to be installed to get the engine up to operating temp. You'll know when it finally burps through the heater core you HEAR IT inside the cabin, a loud gurgling sound and the radiator will immediately need to be refilled.

 

Would there be any reason not to use a vacuum fill method for coolant? I recently picked up one of those venturi vacuum fill deals that you use an air compressor with for my Land Rover. I bet it would work on the G also. I need to do a coolant drain/fill on my 06 G35x also.

 

Never used one before so I have no opinion on them.

OP something I just noticed when I re-read your post:

There is no "adjustment" on the bleed screw, you simply remove it when you are SLOWLY filling the radiator with fluid and reinstall the cap once coolant starts to overflow from it, torque to 11 INCH lbs. I suspect the mechanic simply dumped in a bunch of coolant instead of the < 1 qt per MINUTE as specified in the FSM and probably trapped a ton of air in the system, it wouldn't surprise me if you removed the purge valve cap and nothing came out.

 

Thanks for the feedback. Here is some clarification and some additional questions:
A lisle funnel was used several times; the heat was turned on the max, using the manual setting, not the AUTO. As the radiator was burped, and air purged from bleeder screw, heat would only come from the front vents of the drivers side. All other vents continue to blow COLD air. When the car goes back to idle, the drivers side vents stop blowing heat, and blow cold air as well.
I've been told that there is probably more air in the system but that doesn't explain why after repeated attempts cold air continues to blow from the passengers side vents. What could be causing this?

 

Probably just the way coolant is trickling through the heater core unit, my guess is when you remove that air purge screw in the heater hose you will have a LOT of air in the line still. With the engine cold, COMPLETELY remove the screw until coolant flows freely out of it, yes you will need a container under the vehicle to catch the spill You can stick your thumb over the hole to stop the flow and then quickly put the screw plug back in. I recommend you have a second person handy in case you drop the screw plug

Don't overtighten that screw it's a flimsy piece of crap and can break.