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-   -   HVAC blows hot (heated) air (https://x.nissanhelp.com/forums/sentra/31578-hvac-blows-hot-heated-air.html)

filmteknik 07-21-2019 06:46 AM

HVAC blows hot (heated) air
 
Yesterday a friend bought a 2005 Sentra @ 146K miles. Seemed in decent shape with only minor issues noted. A bit of pulsing on the brakes so maybe warped rotors and a bit of bounce to the ride like worn but not blown shocks.

One thing that pleased us was the nice cold air the A/C was putting out on one of the hottest days of the year.

For the record this is basic HVAC with a hot / cold knob not a temperature setting.

But last night as she was testing various features she turned the control knob to the hot end. It blew hot air as expected. But it kept blowing hot air even turned back to maximum cold (blue).

It doesn’t matter how the output knob is set. We’re sure it’s heated air not just non air conditioned.

Any ideas? Did we just have the bad luck to have the HVAC computer fail just hours after buying? Can I replace it?

Further symptoms: Fan blows and speed is still regulated by the fan knob.

A/C and recirc buttons light up when pressed (except fan speed 0 of course.

I’m pretty sure the output control knob is non functional. Think it was properly directing output to different vents before but not 100% certain.

Compressor is clutching in normally.

Have not yet checked the R134A charge. Could low charge make it do this? I understand no cooling but this is actually blowing hot.

I seem to recall that the seller’s CL ad, now gone, mentioned the nice cold AC. If he charged it just for the test drive and it’s actually a leaky system and it already dumped the charge I get lack of cooling but not blowing hot and the output knob not working. So I think it points to the computer but what say you all?

mpe235 07-23-2019 04:29 PM

Sounds like the cable for the temperature door came loose.

smj999smj 07-23-2019 10:22 PM

If you have manual HVAC, then you likely don't have an "A/C computer. Anything's possible, but I would suspect a bad air mix mode door actuator. As with anything, you have to do the diagnostic steps for the symptom, which are located in the factory service manual for your vehicle. You can access a free, online FSM at Nico Club's site:

nicoclub.com/nissan-service-manuals


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