No way to shut off air cond. cold air

XJ6 1978 ser.2
no way to control the cold blowing air, is it the amplifier or the converter?

No way it blows warm air,

                                                           Walter

I would first suspect the amplifier.
You can easily check that the servo works with a 9v or 12v battery, details in the archives and in Kirby’s book.
Other possibilities could be the potentiometer at the servo unit and the ambient temperature sensor (thermistor).

You likely have early AC version, Walter without the amplifier?

In the early version the heater valve was opened by vacuum, so check if the heater valve operates, and has vacuum?

Frank
xj6 85 Sov Europe (UK/NZ)
**

1 Like

Hi Walter,

try to check the 1A fuse of the amplifier. If it is blown, there will be no servo control. Fuse is located behind the small LH cheek panel attached to the transmission tunnel.!

amp3
André!

Thanks, I’ll check the fuses.

Walter

I’ll check it, thanks.

Walter

I checked my vacuum hose yesterday for the hot water line valve, the hose might have been a
little loose.
Started the car up to check the vacuum line to the valve , it pulled the valve open.
After that the warm air was blowing into the car from the heater and everything seems to be OK.

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‘…seems OK’ is likely as good as it gets, Walter…:slight_smile:

Frank
xj6 85 Sov Europe (UK/NZ)
**

Andre!
It happened again, the cold air was coming in instead the heat.
Could it be a bad thermostat on the right side?
Walter

Now we really do need to know what AC set-up you have, Walter - ‘Del 1/aftermarket’ and Del2 needs entirely different approaches…

Frank
xj6 85 Sov Europe (UK/NZ)
**

Hello Walter,

Please check the two hoses to the heating radiator. Are both getting warm? If not, the water valve is defective and should be replaced. The water valve opens with NO vacuum.

What happens when you change the temperature? Do you hear the servo control unit (it sounds like a little electric motor)?

André

It’s pretty safe to say that Walter has the Delanair Mk II.

All Series II cars to the USA had climate control. And all Series II cars with climate control used the Delanair Mk II system.

There were of course the “heater only” cars, which couldn’t have been but a tiny percentage of production… and USA market cars were not configured that way.

Cheers
DD

In which case the AC am-p would be the prime suspect, Doug?

In which case; the AC being in ‘cooling’ mode should open the center vents…as a crude indication?

Frank
xj6 85 Sov Europe (UK/NZ)
**

Thank you Frank

I’ll make some more tests this weekend to check what happens as it

warms up. Make some notes.

Walter

As usual, yes…after all the easier (and less expensive!) possibilities have been eliminated.

Yes, and when in heating mode, most of the output going to the lower vents. Together these responses suggest the system at least understands temperature change requests and is trying to comply…even if 100% success is not achieved.

Square one, though, is turning the temp knob and listening for the whirring of the servo. A no-whir situation must be fixed first.

Cheers
DD

Took the car out for a good drive to test the air cond, well started up well,
I did not turn the system on, waited till it warmed up, it put out heat.

It turned out heat, then I turned the system on, to LOW.
Temp was set between 85 and 65.

After a few minutes it had some cooler air come in to mix with the heat,
and everything seemed to be OK .
Walter

**
The ‘Low’ and ‘Hi’ setting only controls the fan speed, Walter - the AC amp still controls the cooling/ heating…

In ‘Auto’ the system also controls fan speed; the fans will run at high speed until the set cabin temp is reached. It then drops fan speeds to low to maintain cabin temp - using fan speeds a prime control of cabin temp. A sign of a well functioning system is fan speed variations…

As an aside; when the cabin temp is below set temp - system goes to heating. If above; system goes to cooling - ie, if the cabin temp is below set ‘65’; the system will go full heat. And if above ‘85’ - the system will go full cold…:slight_smile:

Frank
xj6 85 Sov Europe (UK/NZ)
**

Thank you very much for all that information.

Walter