Heater only warm when recirculating?

[HJ2]

Dear all,

A Friend's Elan is having some problems with the heater. It only warms up when recirculating.
I am thinking off:

* Blocked heater matrix
* Broken ducting (the flex section under the wheel arch is probably gone)
* Wrong thermostat
* Vacuum leak in the piping somewhere.

I just installed new hoses + heater valve. You can see the valve operating, but it makes the complete motion when switching (the temperature regulator) from '0' to 1, so higher settings don't do anything on the heater valve anymore.

Anyone experienced the same that can help him pinpointing the culprit?

[Fredjohn]

Hi HJ

The matrix may well be blocked.

However, the movement from 0 to 1 controls the heater valve completely: it is either open or closed. Movements from 1 upwards only move a flap in the heater box to blend different amounts of hot or cold air.
Moving the distribution knob you should, with engine running, be able to hear the movement of each flap as it goes from screen only to recirc. If you can't hear the clunk clunk of the flaps with accompanying hiss, then the vacuum pipe has come lose somewhere. Check the feed from the back of the head on the induction system, then follow into the wheel arch (LHD driver's side): remove the wheel arch cover to reveal the vacuum tank: the pipes often fall off this. Then the pipe goes a wandering behind the dash. That's when it gets difficult!!

Hope this is enough to get started: also check out the w/shop manual pictures of the heater system (5 or 6 position as applicable) This is really helpful in figuring out how it works.
Good luck
John

[epipete]

As John says above, but since the valve is operating to let water through to the matrix let everything cool down then with the heater set to cold try running the engine until the hose supplying the valve gets hot (the return hose should be cold) then turn the heating on and see if the return hose gets hot, this will prove that there is a circulation through the matrix.

The vacuum supply is, again as John says, off the back of the engine (plenum) it's a 2 or 3mm pipe that runs from the plenum to the bulkhead and then runs across the top of the bulkhead down into the wheel arch where the canister is located, you'll need to move a wheel and the liner to gain access!

Good luck

[HJ2]

Thank you both for this enlightenment

I can hear an angry snake hissing so i suspect this is the cause of all misery
Good to know that the heater valve operates normally and that i now know how it works.

So the vacuum canister is sucked vacuum through the pipe between plenum and canister, and the heater vacuum pipes in their turn are connected to the cannister?
Oh well, I will get the manual out first

[epipete]

http://www.lotuselanm100usa.info/heater ... vacuum.jpg

This is an diagram of the Vacuum System, sent to me by BCN, at the bottom is an image of the 'bung' that fits to the back of the heater distribution knob on the dash. This can be removed, just pull it backwards (it's a bitch to put back though!) via the radio slot or maybe the binnicle. Pipe no 2 should have a vacuum as this is the far end of the hose coming off the vacuum reservoir. Note that pipe 6 is also fed via pipe 2 and since the water valve is working this might imply a vacuum is arriving at this valve, the micro switch is operated by the hot/cold knob (when cold a lever presses against the switch and closes the vacuum - the lever runs under the heater matrix and can be felt below between the footwells). Draw your own conclusions

You now have a vacuum route to check from the plenum to the vacuum reservoir and into the heater distribution knob with minimal dismantling. If you don't have vacuum at #2 then the problem is prior to this and if you do have vacuum the issue is beyond it.

If you have vacuum at pipe #2 and feel that you need to inspect the other hoses, I think I'm correct in advising that you can access them all by removing the facia, if it is a problem internal to the heater box then the Dash will need to come out!

Happy hunting

[Rusty Wishbone]

Thank you for making this posting. I have been unhappy with inadequate heat & airflow from my heater, but now that I have tried recirculation mode, I have lots of very warm air!