HVAC Diagnostic Checklist

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Apr 26, 2021 | 07:03 AM

MZX

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From: South Carolina

HVAC Diagnostic Checklist

I am looking for a diagnostic checklist that I can step through to fix my HVAC system. There may be something on here, but I was unable to find one.

HEAT:
Temperature gauge operates as it should. When heat is turned on, the cabin only warms up what feels like 1 degree warmer than outside.

A/C:
Topped off the Freon and compressor kicking on and off as it should. A/C in cabin is only cooling what seems to be 1 degree below outside temp.

With the key in the on position but the vehicle is off, spinning the temperature **** from cold to hot and from hot to cold, I hear movement in the climate control, so I believe the actuator is working.

They may be two sperate issues or they may be the same issue. I do not know.
I appreciate any assistance.
Thanks

Apr 26, 2021 | 10:39 PM

steve(ill)

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if you have no heat and no AC... i would look at the control **** slipping on the shaft, or the BLEND DOOR flopping around inside the duct.. You would still hear the actuator working.

Apr 27, 2021 | 06:34 AM

projectSHO89

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From: St Louis

It helps if you identify EXACTLY what you are working on, including which HVAC system is involved.....

Apr 27, 2021 | 06:57 AM

MZX

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Joined: Apr 2021

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From: South Carolina

Quote:

Originally Posted by projectSHO89

It helps if you identify EXACTLY what you are working on, including which HVAC system is involved.....

My apologize. It is a 1998 F150 XL with the 4.6 and manual everything.

Apr 27, 2021 | 08:34 AM

steve(ill)

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Apr 27, 2021 | 08:38 AM

steve(ill)

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Apr 27, 2021 | 11:29 AM

projectSHO89

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From: St Louis

Could be anything from the stripped **** already mentioned to a faulty temperature control to a jammed blend door to a failed blend door actuator. Of course, it could also be two problems. One would be no hot coolant circulating through the heater core, the other would be the refrigeration system isn't working. Suggest checking the temperature of the pertinent lines/hoses so you know which side of the firewall to focus your efforts on. Failure to do so often results in wasted time and money chasing the wrong thing(s).

Check out the HVAC FAQS, link is in my signature. Most of this stuff was covered over a decade ago when I wrote those.