Hi to all, I try to explain my problem with my bad English.
on my '90 xj when I put the climate control in heat position I haven't air in anyone place! Obviously the fan run....
in vent position the air comes (cold or hot, depending by cursor position, but on red position isn't so hot).
in defrost position the air comes properly on the windshield.
suggestions?

 

+1 I have the same issue

 

First make sure your heater hoses under the hood are getting hot. If they are, you probably have a plugged up heater core.
You can flush it with a water hose both ways but be gentle as its probably on the frail side due to age.

If your hoses are not hot, you probably have a thermostat problem if your system is full of coolant.

I don't know if your 90XJ has a "heater control valve" under the hood but it also could be a problem.

Good Luck and keep us posted.

 

A 90 would have the Heater Control Valve (HCV). This is the part in the heater hose lines between the thermostat housing/water pump and heater core. It is vacuum controlled.

If the air is not flowing in the proper vents according to your control panel, but DOES flow as if it's on "defrost" all the time, then this means there is a vacuum problem since the air flow is controlled by vacuum.

If I'm reading your description correctly Steve, it sounds like both things are happening. This suggests to me that you have a vacuum leak that is affecting both the HCV AND your vent doors. I would look for a vacuum leak and repair that and see if it corrects everything.

Once you have your vents running correctly and the heater control valve running correctly, you should look into -eliminating- the heater control valve. The 97+ XJ's do not use a heater control valve and you can buy the hoses for the 97+ XJ and they fit perfectly. Then you simply plug the vacuum line for the heater control valve and your heat will run correctly and you won't have stagnant coolant sitting in your heater core all summer. This can help prevent heater core failure by getting fresh coolant with fresh conditioning chemicals flowing through the heater core. I eliminated the HCV on my 95 and it has worked great for me so far.

I hope that translates correctly into Italian. Good luck and let us know what you find!

 

I agree

 

I don't think I have a problem with the vacuum line because I listen and see the door "lever" move near the passenger's feet and because when I move the cursor to the def position the air only blows towards the windshield and nowhere else; when it is in the vent position, the air comes out of all the vents, as I believe is correct, whenmoreover, the air temperature is adjustable, from cool to warm, not hot.
When the cursor is in the heat position the air does not come out anywhere ... obviously the fan always works

 

The Heat setting should be blowing on the floor with a small air flow onto the windscreen. When in Defrost you should get air on the windscreen with a small flow onto the floor.

If it is working correctly I'd suggest looking back at posts 3 & 4.

 

This morning I used my jeep. Actually in the heat position the air reaches the feet and the windshield, so it's as you say, it works. I believed that in heat position the air would be warmer and that it would arrive in the same vents as in vent position. For this reason I thought I had a problem. Probably it is the thermostat that causes the air temperature not so high, since in use I do not go beyond 70 ° C

 

If you think it may not be the climate control have you checked that the blend door that controls the air temp is fully opening and closing? It's down on the floor on the passenger side footwell and is controlled by a cable. Mine became disconnected and was allowing the cab temp to vary.

 

I'll check the opening of the blend door today.
However the water temperature does not rise enough (70 °). Will change the thermostat immediately. what is the correct opening temperature? I found several (87 ° C, 80 ° C ...)

 

I believe the thermostat should open at 190 degs F, which is about 87 degs C.

I will also recommend removing the HCV.

 

Remove?

 

The heater control valve. It controls coolant going to the heater core in an On/Off manner.
Right hand drive XJ's never had them and they were completely iliminated in the 97+ XJ's. If it's not opening fully, it will restrict coolant (and therefore heat) going to the heater core.

 

^^ yes. It was eliminated on the '97+ XJ's. You can get longer hoses or preformed ones for later year XJ's. Can't remember the year right off but someone will post it I figure. You have to plug off the vacuum line that operates also.

The HCV becomes VERY brittle after years. Mine self destructed luckily while parked in front of the house.

 

Mine never had one but that didn't stop nearly every other component of the cooling system self destructing