01 not blowing hot air

i have a 2001 jeep cherokee that doesn't blow hot air, it blows lukewarm air, on fan speed 1 and 2... 3 and 4 just blow semi warm air, but more so cold air. I have replaced the thermostat (few days ago) new radiator (year ago) along with waterpump (year ago). i have done some research and dont exactly know what to do, i'm thinking maybe the Blend door, or something. I'm not to familiar with this type of problem, i know quite about about engines, just not the electrical, or climate part :(..any advice or tips would be appreciated.

I have had the same problems as you over the last year and recently had the same heat problem and it was my heater core. I saw water dripping down into the front passenger side floor. it wasn't an easy fix. The whole dash had to come out to get to it. Not sure if that is your problem but it could be.

Some basic questions:

What is your temperature gauge reading on your dash? If it is around 210, then your thermostat is good. If not, then you might want to look at a new thermostat. THEN....

look under your hood for the two heater hoses that are going into the firewall on the passenger side. reach onto them and see if they are both hot while you have the engine warmed up with the heat on.

If they are both hot, then you are likely getting good flow through your heater core. If they are not hot, or if one of them is not hot, then your core might be clogged and need a flush (which is easy to do).

You can look on here to see some other examples of how to do a heater core flush, but a garden hose, some buckets and a screwdriver and pliers should be all it takes with about 10 minutes of effort.

Let us know how it goes.

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If its vacuum operated check to make sure it has vacuum.