Stephen Irons

Hi On my 1978, a month ago the Bowden cable that controls “Heat” became unattached at the control lever – the small plastic retainer had broken - under the centre console. I have managed to re-fix the cable with a small bracket and it appears to be working perfectly. However, since then I do not seem to be able to get it blow cold air at all when the lever is moved to the “cold” position. The A/C is currently non functioning, so I know that it will never be “chilled”, but it did used to blow un-heated air on anything but a really hot day.

As I understand, the cable goes to a flap/door in the heater assembly and closes this off as it is moved towards the cold setting. I am wondering if when the Bowden cable came adrift, it may have detached itself from the flap operating lever?

So, this long winded post is to ask if it’s possible to see the flap lever if the glove-box is removed? Based purely on looking at the manual, it seems to be in the area behind the glovebox, but before I get into removing it I just wondered……. ?

Additionally, I think I’m right in saying that the vacuum operated valve in the heater pipes is only operated when the “A/C-Vent/heater/defrost” lever is moved across to A/C – is that correct?

MelWff

have you tried just looking under the dashboard?

CaseyJones

I think you can see the flapper at the passenger kick panel if the panel is removed. Not sure if you can get to the one you need without at least removing the glove box liner. That is where the cable terminates at the top of the airbox anyway

hunt4cleanair

That's a possibility but the vacuum controls may also contribute.

Its actually below it but behind the ductwork

Stephen

You have vacuum operated actuators (valves) at each kick panel that bring in fresh air directed to the dash side vents; a defroster actuator that chunnels in hot air or a mix for defrost requirements; A/C actuator to direct cold air to the dash center vent and than the heat underneath as you describe. You're problem could very well be with the vacuum connections (pipes) that are white under the dash. In fact under the hood, you can trace where it comes in through the firewall.

The challenge is access to these various actuators...I have done it, its a fun project but it requires patience and removing the passenger seat, the center dash console, the glove box and removing the ductwork from the center console to the passenger side. This way you can see and trace the vacuum pipes to the actuators. If you have a vacuum gauge and pump, you can test the actuators to ensure they are not leaking while checking they hold vacuum and operate as intended.

My 78 blows heat all the time or I should say it emits heat which usually comes up through the console tunnel and this is not an unusual complaint for late model C3s.

Hope this helps!

Stephen Irons

Hi Tom

Thanks for this!

This little “issue” has only appeared since the cable bracket became detached from the lever assembly, which is why I suspected the far end of the cable may have been affected also. I’d looked at the AIM, but wasn’t sure if it was accessible behind the glovebox.

So, I removed the glove box last evening and sure enough, there is the lever and the vacuum switch. It appeared that even with the control lever pushed fully over to the cold position, and despite adjusting it with the screw adjuster assembly, the heater box lever would not fully depress the switch button. Now, the end of it may be broken, and as the problem is new that’s a possibility I guess, but, it al looked present and correct!

Anyway, I made a small “pad” that slipped over the end of the lever, spent some time adjusting the cable (thankfully, I can remove the centre consol side panel with the seat in situ!) and I’m now pretty sure that when the control lever is pushed fully to the “cold” position that the lever on the heater box fully depresses the switch button.

I hesitate to say it, but at the moment, as far as I can tell, the various vacuum valves that operate the ducting “doors” are doing what they should be. I’d sheathed the tiny vacuum line that goes to the under hood valve some years ago, as that was cracked and leaking. Although we we’ve never had “cold” air, it was at least “unheated” before this little issue, so I’m hoping I may have cracked it now! We’ll see on our next run out!