Took a quick Holiday jaunt in the '95 XJS from NC to Philadelphia and back last week. Left NC and it was a little cold, so, turn on the heat. Just wasn't blowing hot air. Temp needle was pegged on C. Over a 500-600 mile drive, it wasn't moving above the C. If I did some stop and go driving in DC or Center City Phila, it rose a bit, but still pretty close to C, and still no hot air.

Before the trip I checked my coolant level, and it was a bit low, so I topped it off. This is the first I've noticed the all cold air/no heat thing. Before I added coolant, I was getting the temp needle into the mid point between C and H. That was 2 weeks ago.


Anyone ever have this issue? Thanks!

 

I suspect your thermostat is stuck open

Cheers
DD

 

I have this issue but I doubt its the coolant itself, it is basically 45F here right now in Freedom Units, or about 7C car engine is comfortably warm and a bottle of winter warm-up additive did help but my heater core valve wasn't doing it's job.

I disconnected the vac line and found the hole to the unit so small and deformed it couldn't possibly work. I simply left the vac line off which, if I'm not mistaken, is the default full flow position. My car's climate system started blowing hot air again!

Remove the small hose and tape it off, maybe squirt some WD40 in there and around the unit and manually move it abit with a screwdriver (like a pry bar) make sure it actually will function. That should get more hot coolant to your heater core assuming your system isn't clogged with 30 yrs of crud.

 

I think Doug has it right. if it was the heater valve wouldn't the temp gauge still read correctly?

 

I'll look into that. Thanks for the suggestions