Bought my 04 XJ last August with 70,000 miles and when winter came around the heater was not blowing out hot air. More of a luke warm feeling. Also the vents on the driver side was blowing colder air than the passenger side. I believe one of the vents are not working properly. I changed the thermostate and it began to blow a little warmer but not nearly as much as it should. Any remedies would be helpful. The weather in NY is getting serious!

 

Is your blower fan working-is there a good flow of air from the vents? If there is a good air flow but no heat it is possible that you have a blocked or partially blocked heater matrix. Have a feel of the two hoses about one inch dia on the left side of the engine-they are flow and return from the heater-are they hot?
If you think that there is a blockage one of the members on the Uk forum has sccessfully flushed the matrix using a garden hose.

 

There is a eletric waterpump or aux pump for the heat. Make sure that is working or the fuse isn't blown.

 

I looked in my owners manual and it says heater circuit water pump. Is this what Im looking for

 

Also, in diagnosing, check to see if you have heat on the passenger's side and not the driver's (assuming is is from the criver's side that you discovered no heat). The left side heater core has a "habit" of clogging, preventing heated coolant from entering that side.

 

Yes, check the fuse and you should be able to feel it hum if you touch it.

 

I checked the fuse and it was blown. I started the ole' cat and checked lines into the heater matrix. The two lines into the dash are hot and the two coming out of the dash are cold. Does this mean there is a blockage?

 

When I look under the hood there are two sets of lines running into the firewall. One from the left side and right side of the engine. Each side has two lines runnning together so all together its 4 lines. The left side(passenger side) lines are hot and the right side(driver side) lines are cold. Are the lines on the left for the air conditioner. If not then would this mean that the driver side of the heater core is blocked? Would a flush help or should I bite the bullet and change the heater core at this point.

 

I wish someone would have answered Mistchachin's question about the core (matrix) change...

I have this same problem... no hot air coming to drivers' side, anywhere: defroster, floor, or dash vents... Passenger side has lots of heat...

A while back I had a water leak. I first tried using some kind of 'stop leak'... (Please don't castigate me now!) and while the engine was running
I forgot to turn heater on high (major screwup!).

It is my belief that this caused my heater core (matrix) to clog...

1. Is it possible to back flush the core without removing it?
2. Will the 'stop-leak' permenently clog the core?

I gleaned lots of debug info reading this post and will check out the fuse, pump and temperature of the hoses...

Merry Christmas and Happy New Year to y'all.

Kyd

 

I have the same problem did not find that out until yesterday, the far left hand side vent is blowing cold air only, all the other vents are working great.I will check the fuse, cross my fingers and hope that it.