Dear Auto Advisor, I have recently purchased a 2005 Dodge 1500. All seems to be well except the a/c and heater. The A/C blows cold going down the highway, but blows warm when I sit at red lights. I have also noticed that when I turn the heater to hot, only slightly warm air comes out of the ducts. Any ideas where I need to start?
On the a/c system it sounds as if the condenser fan is not working. You said it blows cold going down the highway but warm sitting still. This is normally a condenser fan problem on this model. Just open your hood while you have the A/C system turned on. Look and see if the compressor is short cycling (cutting off and on every 30 to 40 seconds) if it is short cycling, see if the electric cooling fan for the condenser is working. I suspect this little electric motor has quit working or is unplugged.
Now to the slightly warm air when you turn on the heat. First thing to do make sure you have plenty of coolant in the radiator. In most cases this is why this model does not heat well is low coolant level. Other areas of concern may be due to a clogged heater core or a faulty blend door operation. If this is the problem you will need to do some more testing and inspection. So check the basics first and get back with me.
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