octigonwallrus

im really starting to freeze(its been in the low 30s last week or so). ive had my 98 xj for over a year now, and the heater worked when i got it(not real good though). but now it doesnt work at all.
it blows cold air. but not hot air. im getting water circulation.
fuses are all good.
any help would be great.
thanks
ryan

StillwaterEMT42

Might be your HCV (Heat Control Valve). I'm pretty sure the 98 series still has them. Its a small black cylinder to the left of your manifold, its got a thick black hose coming to it and then a small vacuum hose into the top. (the vacuum hose was gray on mine). Sometimes that sticks, have someone turn your heat on and you should see the vacuum move in and out of the valve. If its not moving, spray it with some WD 40 and hope for the best.

SeriousOffroad

No heater control valve in 98 XJ's.
Just fixed mine, same problem. Ever replace a heater core in an XJ? You're in for a real treat.

StillwaterEMT42

Okay, thanks. Wasn't sure what year they stopped using the HCV. Good luck!

asatxj

Start by flushing the heater core. do it both directions for a lot longer than you think you need to. While doing that pray often that you don't need to change your heater core!

Bent/Bolt

Although not my thread i would like to thank you all for the advice.I too was having problems with heat out-put.Today i ran my cherokee and kept checking the HCV.This valve never moved,tried back and forth 12 times at 210 temps.looks as ill replace this tomarrow.Also i noted that its vacum operated.Should i check for vacum.or does it only operate while turning the heat lever?

muddeprived

looks like i'm not the only one getting N.E.

jonb8

My wife's 98 was plugged up with that crappy red antifreeze. Flushed it good and heater works great now.

BowtieGuy3

Just to let you all know...Dex-cool sucks. I don't even run it in my GM that it came in...100,000 mile antifreeze? Not in this world. I recommend no one ever uses it, not even in a GM...

XJ Stryker

Do not use high pressure the last thing you want to do is crack it and it start leaking on ya.

Ask me how I know... I used to have a 98 Blazer with a heater problem I tried about 3 times to get that damn heater core out, so if this if anything like that then all I have to say is good luck.

asatxj

Thanks Stryker! I forgot to mention that flushing basically means use the garden hose with low pressure. That's why I said do it longer than you think you need to.

haro

I got ahead of my logic and now have some better answers and questions. 2001 Cherokee.
1. appear to get "warm air" out of dash vents (**** on chest symbol) with temp control on highest red mark. Air is cooler out of vents (**** on foot symbol) when I turn it toward blue temperature marks gets colder.
2. Temp gage on dash 210 steady, but I notice it gets up to temp quicker than I would expect.
3. Heater hoses hot. Difference in temp, can not really tell
4. anti-freeze looks good under radiator cap and in expansion tank. No oil
5. Which heater hose goes into heater core? On firewall top or bottom one?
6. Dash symbol has me confused, symbol with arrow towards chest and symbol with arrow towards feet. If I read manual correctly, only feet symbol is for heat and chest symbol only for air vent from outside.
7. Been too cold out -17 to remove glove box and look at blend door actuator or remove actuator and try moving shaft (key in run position) while turning temp dial from hot to cold.
8. Fan speed switch works fine, air distribuation switch works fine (defrost, dash vent, floor vent, etc)
9. If I can back flush heater core is there any cleaning solution that can be poured into heater core before flushing?
10. I assume thermostat is working and in correctly. Just bought car and it needs lots of TLC. Found head light in upside down, defroster switch broken, 12v aux socket- blown fuse, windshield wipers pretty much worn off, every joint in hood, doors, wiper arms looked like not lubricated in real long time.

Any thought appreciated.

CCKen

Your Owner's Manual gives all the functions of the Mode Selector settings. Get familiar with them.

Back flush your heater core then get back.

There's dozens of heater core flushing procedures on this Forum. You can use the search function or just go through the last several pages of threads and you should find at least one good one.

SeriousOffroad

Blend Door.....