'97 Q45 No heat

[904Y33]

Forgive me if there's already a thread that has the answers I need, but as of right now I can't seem to find it. If it exists, please link it in the replies.

My Q45's AC blows cold without issue, but no heat comes out of the vents. I've already confirmed that the air mix motor works, I can watch it turn smoothly as I turn the temp dial. I'm suspecting but not convinced that my heater core is clogged, as I'm not getting any heat at all from either side. I will say though that I recently replaced my thermostat and whoever replaced it last time went ham with the RTV, so I'm not ruling out loose RTV clogging up the heater core. I've heard (read) from various sources about some kind of valve that opens to allow coolant into the heater core, but I can't seem to find where that valve is. Where is this valve located and how can I open it if it exists? If I should replace it, how can I find a replacement part? Should I just try and flush the core to see what happens?

[VStar650CL]

Did the problem happen concurrent with changing the 'stat? If so, it's more likely the cooling system wasn't bled properly than anything clogging it up.

Some N/I models do have a water valve that cuts off heat when the A/C is switched on, but I don't see one for your ride in the '97 FSM.

If you want to bleed it yourself, get a no-spill fill bucket, park on a steep uphill with the bucket about half full, idle till the engine is good and warm, then run it at 3500~4000 RPM for about 2 minutes. Remove the bucket and cap the radiator, let it cool off, then top the overflow bottle if needed. If you don't have a steep hill handy, just jack the front of the vehicle as high as you can.

[904Y33]

Did the problem happen concurrent with changing the 'stat? If so, it's more likely the cooling system wasn't bled properly than anything clogging it up.

Some N/I models do have a water valve that cuts off heat when the A/C is switched on, but I don't see one for your ride in the '97 FSM.

If you want to bleed it yourself, get a no-spill fill bucket, park on a steep uphill with the bucket about half full, idle till the engine is good and warm, then run it at 3500~4000 RPM for about 2 minutes. Remove the bucket and cap the radiator, let it cool off, then top the overflow bottle if needed. If you don't have a steep hill handy, just jack the front of the vehicle as high as you can.

I've owned the car for a little over 4 years now, never had heat. Since I live in Florida it's never bothered me too bad, but after changing the thermostat about 2 months ago I was hoping for some results. Since I'm a dealer technician (then Volvo, now Lexus) I had access to a vacuum filler so bleeding was a non-issue. I've also noticed in other threads that people have scanned their cars and found certain trouble codes, but for whatever reason I've only ever been able to communicate with those cheap handheld scanners AutoZone will let you borrow, no bigger scan tablet has been able to connect with my car so far.

[VStar650CL]

Then if the mix actuator is moving visibly there are really only two possibilities, a blocked core or a broken mix door. You can probably tell which just from some touchy-feely on the hoses with the mix door on full heat and the blower on max. If both sides are warm-but-not-hot then there's a flow problem, if both sides are too hot to hold comfortably then the core is open but it isn't losing any heat. Normally the inlet should be very hot and the outlet should be hot but noticeably less.

[Sapofeo]

My car also does this. You can run a diagnostic as described on HA-29 in the FSM. Mine came up with "Bilevel door motor" which is different from the mix actuator. I can no longer find the part. Someone on here goes through the glove box and physically moves it at the beginning of Summer and Winter, depending if they want hot or cold air. I have a 2000 AE.

[VStar650CL]

My car also does this. You can run a diagnostic as described on HA-29 in the FSM. Mine came up with "Bilevel door motor" which is different from the mix actuator. I can no longer find the part. Someone on here goes through the glove box and physically moves it at the beginning of Summer and Winter, depending if they want hot or cold air. I have a 2000 AE.

If you check out the door diagram on HA-20, provided the mix door is open, there's no combination of mode door positions (including the bi-level door) which can completely cut off flow through the heater core. The bi-level door can reduce the flow, but hot air will still come out someplace (just less of it). The only things which can cause a zero-heat condition are a blocked core or a stuck mix door.

[Sapofeo]

I can see the mix door moving (I believe that's the one you can see from the driver's side foot well). If that's the case, it could be something different. I was going by the error code I got when running the diag. Thanks for the info.