Hyundai Sonata Heater/Blower Issue

Maintenance/Repairs
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1

I’ve stumped the local dealership and their Hyundai Tech Line as well. This is a 2011 Hyundai Sonata with about 50k miles. Also this is my first winter with it so I can’t tell you if it’s a new issue or if it’s always happened in the “cold”. This is Northern California so the cold nights are about as low as 30.

On a cold start, after 20-30 minutes the heater sputters out and the lights on the control unit go out. Sometimes it goes back on if I continue driving for 5-15 more minutes; another way for it to go on again is to turn the car off and start it again. The final way to turn it back on (which was discovered the last time it was in the shop) is to gently begin to start the car again (while it’s on) and just that slight movement in the ignition cylinder turns it back on.

The sputtering out doesn’t actually turn it off completely, just the lights, buttons and knobs stop responding and the heat mostly goes off.

The control unit has been replaced, plugs have been tightened and the ignition cylinder has been replaced.

They’ve road tested it 3 times and I’m a little tired of having to get a rental car as they claim to not be able to start a new case with Hyundai Tech Line until they have my car.

Please help!

2

There is a FET that is between the blower and the AC control module. This is what controls the the fan speed.

3

From what you say about the ignition switch it seems replacing that should have cleared the problem. Perhaps it is the ACC contacts of the switch that have the problem, which normally provides switched power to the things you mentioned. There could be a problem with the wiring to the switch but it sure seems the switch was causing the trouble from what you stated about it. I assume the shop really replaced the ignition switch section and not the key lock cylinder. Adjusting the switch position may solve the problem.