We were having some issues with the fuel gauge sensor and sent the car in for repair. They replaced the fuel sending units and the associated sending module and that fixed the problem. However, a day after we got the car back the heat stopped working intermittently. Now it seems there's no heat at all. Airflow is fine, but only cold air is blowing out of the vents.

Any suggestions on what to look at first? I'm not sure if this issue is just a coincidence with the recent work or if the recent work may have caused this problem.

Any guesses or typical issues that cause the "loss of heat" problem?

Thanks in advance!

 

check coolant level.give the duo valves a tap with the handle of a screw driver,they may be stuck.
sometimes a reset of the cars ecu will solve the issue,so if you disconnect the neg terminal and step on the brakes for 30 seconds and rehook the terminal,it may clear the issue.in your manual is the other procedures to do after installing a new battery,which is basically what you tricked the system into thinking you have done.
ohlord
if none of this works you need to make sure the engine coolant is heating up,so after running 15 minutes what does the display read?

 

it could be something as simple as the thermostat being stuck open. might want to pressure test.

 

My 2003 E320 stopped heating a couple of weeks ago, AC was fine, but no heat. I just sold the car last week, so I never had the chance to know what was wrong. Good luck.

 

"so if you disconnect the neg terminal and step on the brakes for 30 seconds and rehook the terminal,it may clear the issue"

What does this procedure do?

 

Resets the cars systems,sometimes it will fix a climate control problem,failure to boot the cd changer,brake light abs warning light faults and a lot of other systems controlled by the controller area network modules and the ecu.Worth a try.Before going further with more tests.
ohlord

 

did all of the above twice no go; any other suggestions?

 

My guess would be the heater valve 211 832 05 84 retails for about 37 bucks.
If it's not bad it will be so you're not wasting money by replacing it, even if it doesn't solve your issue.