Not enough hot air

[asquithea]

2010 Lotus Elise SC:

I'm not getting enough hot air from my vents. Apart from being a bit chilly, it was a bit of a bugger this evening as it couldn't keep the screen properly de-misted while driving in the pissing rain. Seems like I get a bit more heat when the car is stationary. Engine temps are stable and normal, and the coolant level is fine and also stable. I _think_ this came on after I had the rad changed - the old one was leaking. The new rad is a single-pass pro-alloy.

Airlock in the system? Anything straightforward I can do to fix it? I can't see anywhere I can do any further bleeding. Or is this somehow expected with a non-stock rad?

[k20erham]

Hi 2010 I'm not too sure, on mine a 2006 S/C with A/C the flap was seized mid way in the heater box, which if it's the same on your car is a clam off job. On mine the heater matrix always gets hot water (there is no valve) but when you select the A/C a motorized flap blocks off the hot side and lets the cold A/C matrix air into the cabin. other clues on my car were A/C was not good, but since I have done the flap it is icy cold, or very hot dependant on selection. I did not have to remove the heater box, (massive job) I just freed it off and lubed with white grease.

[asquithea]

Balls. The 2010 SC probably has the same setup as yours. Mine does have a/c. Condensor was replaced at the same time as the rad, but the regas didn't last long so it's either leaking elsewhere or part of the problem as you suggest. Probably both :-/

I'm fairly sure the vent selector is still working. If there's a separate flap for hot air selection, I guess I can diagnose whether it's stuck just by turning the fan on and moving it between the hot and cold positions? Maybe it's just lost some of the range of movement.

Edited by asquithea on Tuesday 11th June 10:18

Edited by asquithea on Tuesday 11th June 10:19

[k20erham]

Hi mine was stuck right in the middle, mine had the sill pipes and fan electrics done a few years ago, I then went through most of the o rings on all the joints until I found where the gas was leaking from, which was one of the steel pipes that join the aircon rad (just under the front clam, the alloy rad threads corrode in the steel nut, so I had to change the air con condenser rad, but you also have to clean out the steel nut from the corrosion or it does not seal properly.

[asquithea]

I pulled the access covers, and found that the hvac hose wasn't really seated properly. Enough of a gap for me to peek an endoscope in there (thanks to all the various people who have posted to PH and other forums explaining what to look for), and I could see the flap moving - but kind of spastically and seeming to need a bit of fan assist. Can't tell if it has full range.

I couldn't really get a hand between the pipes much less lube the movement, but was able to poke the hose a bit to close up the air gap. Hopefully that'll improve things a little. Suspect I'll have to be satisfied with that. Thanks also to k20erham for the input.

[k20erham]

Hi, are you sure you are looking at the correct flap? The one I'm talking about under the front clam and requires the large air feed duct pipe pulling off, then you can see the flap, which has foam bonded to it, it moves left to right quite slowly, when it is all the way to the left side of the box you get cold air from the A/C matrix (when it's turned on) and when its all the way to the right side of the box you get hot air from the heater matrix, if your flap sticks and your A/c is working ok you still only get warm air as the heater matrix is always hot and the flap does not blank it off.

[asquithea]

k20erham said:

Hi, are you sure you are looking at the correct flap? The one I'm talking about under the front clam...

Big corrugated tube accessible from the passenger side; silver matrix; foam bonded flap - all check. I'm fairly sure I had the right flap thanks to previous description, but I couldn't get enough access to remove the HVAC tube without risking making it worse, so had to settle for peeking through a gap with it slightly dislodged.

Endoscope showed it moving when I turned the heat control, but I didn't have enough visibility to see if it was a full movement - and I think it's binding a bit.

[k20erham]

Sounds right, I sprayed White grease on mine, I did not take it apart, then manually assisted it side to side until it would move its full range unassisted, don't be tempted to spray WD4* or similar as those can destroy some plastics/nylons and will smell in the cabin ETC

[Mike-tf3n0]

I'm not familiar with the air-con system in your car but if you have a separate heater then you may find the answer at T7Design who are now making very nice replacement heaters for the VX220 which is, in this context, identical to the Elise S2. My VX220 heater suffered from a seized air flap before the plastic casing finally turned to cheese full of holes. You will find loads on the VX forum about how to replace the old heater with the new.