Alfa Romeo Owners Club of Australia Forum

Technical => 116 Series (Alfetta Sedan/GT/GTV & Giulietta Sedan) => Topic started by: AlfaACT on November 11, 2020, 11:55:00 PM

Title: Air Con concerns
Post by: AlfaACT on November 11, 2020, 11:55:00 PM
Seeking advice on the air con plumbing in an Alfetta coupe:

There are several matters I would like to resolve, so one at a time.

First: Is this a standard heater tap (for an Alfetta coupe)?
Title: Re: Air Con concerns
Post by: AlfaACT on November 11, 2020, 11:57:28 PM
2.   The Heater Tap pipe

The heater tap has a small pipe emanating from within it that follows a circuitous path then disappears into the heater box. The other end is not attached to anything, and is not anchored. It just lies between the heat exchanger and the fan motor.
First photo shows the heater tap & pipe in detail, the second shows the route the pipe takes.
Q: What is its purpose?

Title: Re: Air Con concerns
Post by: AlfaACT on November 11, 2020, 11:58:46 PM
3.   Spurious pipe #1:

This thin copper pipe runs across the gap between the inlet and outlet for the A/C pipes. It is embedded in the brass fitting at 1 and is tightly coiled against the second pipe at 2.

Q: What is its purpose?
Title: Re: Air Con concerns
Post by: AlfaACT on November 11, 2020, 11:59:53 PM
4.   Spurious Pipe #2:

Another thin copper pipe that traces a route across and along the heat exchanger – but this one is not connected to anything - at either end!

The end labelled “Start” appears to have been cut with “side cutters”.

Q: What WAS its purpose?
Title: Re: Air Con concerns
Post by: AlfaACT on November 12, 2020, 12:00:40 AM
5.   Should these spurious pipes be connected … ?

Q: Should the stub at 1 be connected to the “cut” pipe at 2?

Title: Re: Air Con concerns
Post by: AlfaACT on November 12, 2020, 12:04:12 AM
I should have said, these were all exposed as I had to remove the cabin fan to service it! Ouch.

In anticipation of lots of useful and interesting info - thank you.

OO=v=OO
Title: Re: Air Con concerns
Post by: bonno on November 12, 2020, 09:14:05 AM
Hi AlfaACT
A simple answer to your questions is that it’s a TX valve for your car Air Condition unit. This TX valve controls the temperature and forms part of the A/C system. The cut capillary tube shown is part of the TX valve that has been replaced previously. The heater tap shown looks original or OEM replacement. I have attached a Youtube video that explains the purpose and function of the TX valve. that might better explain.
https://www.youtube.com/watch?v=oSLOHCOw3yg
Title: Re: Air Con concerns
Post by: AlfaACT on November 12, 2020, 12:14:22 PM
Thanks bonno,

"The cut capillary tube shown is part of the TX valve that has been replaced previously." That makes sense!
The video is informative and helpful too.

One (last?) question:

The subject of my Post 3 (the A/C's TX valve) is clearly fundamental to the function of the A/C! I get that now.
But why a TX Valve embedded in the heater tap? See my Post 2.
Does it override the operation of the tap - maybe so that you cant turn the heater "on" if the A/C is "on"?

The heater in this car has always either been fully ON or fully OFF! There was no fine control for heat.
The only way to control cabin heat was manually turning the heater on and off  - i.e. repeatedly sliding the hot/cold lever.
Therefore (sorry, another question!) does this mean that the TX Valve in the heater tap is non functional ???
Title: Re: Air Con concerns
Post by: sportiva on November 12, 2020, 01:00:04 PM
The air-con system and heater also known as the HVAC for my GTV6 has three of these copper tubes the tubes measure the temp at  the evaporator. One tube originates at the air-con temp switch it measures the temp of the evaporator and signals the compressor to cycle on and off. The second tube is from the TX valve it senses the temp and controls the pressure of the refrigerant that flows into the evaporator. The third tube is connected to the heater valve the purpose of it is to open the heater valve slightly to stop condensation freezing on the evaporator. I'm not sure on the tube #2  the three other tubes connect to a device. This tube is connected to the inlet of the heater core so I think it could measure water temp on the way in and air temp as air it is blown through but for what purpose I don't know!
Title: Re: Air Con concerns
Post by: bonno on November 12, 2020, 04:09:31 PM
My understanding of the older style A/C systems, the heater valve is simply a tap to supply water from the cars cooling system and is not tempt controlled. The purpose of the heater apart from warming the car in winter,  is to when combined with the A/C system is for defrosting the windows. As Sportiva has indicated the A/C temperature is regulated/controlled via the thermostatic switch which incorporates a sensor capillary attached to the evaporator to enable cycling on and off.
Title: Re: Air Con concerns
Post by: AlfaACT on November 12, 2020, 07:10:06 PM
As Sportiva mentioned, there is also a third thermo sensor - attached to the A/C cabin temperature switch.

The first photo is of the general layout of the inside of the upper section of the A/C box.

The second photo is a close up of the sensor attached to the back of the temperature switch.
Note the coil of the sensor (1) in front of the air outlets to the cabin and the dash.

The purpose of this sensor, given that it is attached to the thermo switch and primarily located in the air stream to the cabin, seems to be to detect the temperature of the air pushed into the cabin - i.e. the climate control component of the system?
 
Title: Re: Air Con concerns
Post by: sportiva on November 12, 2020, 07:49:58 PM
The sensor tube in your photo originates at the air-con temp switch and ends way out of any airflow, we need someone to confirm that this is the place the factory positioned the sensor or did someone in the past 30 yrs of this cars history just moved it there.
My GTV6 temp switch sensor rests infront of the HVAC core in the air flow. the sensor in your photo is well outside any airflow
Title: Re: Air Con concerns
Post by: AlfaACT on November 13, 2020, 02:29:16 PM
No argument Sportiva. The route of the capillary is definitely not correct, but I am having trouble identifying an appropriate route.

See attached pic:
I have removed the capillary from the small square hole that it poked through before. (cf post above)
Things to note:
1: square hole; (no capillary!)
2: second square hole;
3: inlet for fresh (external) air; (closed in this pic)
4: inlet for cabin/interior air (recirculation mode). 
Title: Re: Air Con concerns
Post by: AlfaACT on November 13, 2020, 02:36:58 PM
Reconstructing the interior of the A/C box is shown in the following sequence.
(Note: as the heater & A/C control switches are in the upper half of the A/C box, the photos are looking at the top of the box, but from below)

First is a separation plate: separating incoming air from the heat exchanger.

Note that the marked/starred positions indicate where tabs on the plate actually insert into the square holes in the A/C box - shown in the previous post. When the plate is properly in place, there is no room for a capillary to poke through!
Title: Re: Air Con concerns
Post by: AlfaACT on November 13, 2020, 02:38:18 PM
Next is the (upper) half of the fan cowling.

Title: Re: Air Con concerns
Post by: AlfaACT on November 13, 2020, 02:41:14 PM
Next is the (lower) half of the fan cowling ...

A point to note here, is that as the interior of the A/C box is assembled it effectively creates a wall between the switch area and the heat exchanger.
Title: Re: Air Con concerns
Post by: AlfaACT on November 13, 2020, 02:44:30 PM
Finally, is this a possible arrangement for the problematic capillary tube ... ?
Title: Re: Air Con concerns
Post by: sportiva on November 13, 2020, 06:31:14 PM
If you were to place the capilary just over the edge it would be in the direct flow the of air through the core. The question is did Alfa originaly place this capilary/temp sensor in the air flow or out of the flow? The above photo is 2D, I know, that from the tip of the temp sensor to the yellow wire is 70 to 80 mm lower you just don't sense that in the flat screen image.
Title: Re: Air Con concerns
Post by: AlfaACT on November 14, 2020, 01:48:52 PM
Here is a pic from in front, showing the (final?) location of the capillary.
The capillary has been relocated a little.
The only concern now is that the unsupported tube is likely to fracture at the switch - and rattle in the meantime. But there doesn't appear to be anything to secure it too.
Title: Re: Air Con concerns
Post by: bonno on November 14, 2020, 03:52:02 PM
For the thermostatic switch to operate effectively, it requires that the probe/sensor to be in the path of air flow being pushed out to the vents and probe centrally secured/cable tied to evaporator. When A/C system is running the temperature at the air vents should be around 6 degrees C.
Title: Re: Air Con concerns
Post by: bonno on November 15, 2020, 08:32:45 AM
Further to my previous post, here is a link to the experts advice on location of the thermostat probe/sensor location (DIY Thermostat Sensor repairs).
http://www.airsupplyinclv.com/services/air-conditioning-troubleshooting-guide/air-conditioner-temperature-thermostat-sensor-problems/
Title: Re: Air Con concerns
Post by: GTVeloce on November 19, 2020, 11:20:16 AM
Hi mate

You have two options with that capillary. Either squish it into the evaporator core or better still, attach it to evaporator return pipe. My 75 has it this way from the factory and I think it is probably the better location as the temperature can vary across different parts of the evaporator but the temp of the return line is probably a better indicator and it means you can get a solid connection. Then wrap it with some of that horrible, black, super sticky tape (I have a giant roll of it if you wold like me to send you some - I'm sure I owe you a lot more that that!).
Title: Re: Air Con concerns
Post by: AlfaACT on November 20, 2020, 02:20:30 PM
Hi GTVeloce,

Thanks!
Re the "horrible, black, super sticky" stuff: I have been wondering if there might not be a 20th C (if not 21st C) solution to this problem! If not, I might need to take up your kind offer. I'll be Dynamatting the floor & firewall - Yep! I have read your post on insulating the cabin - so I wonder if Dynamat might work wrapped around the exposed metal A/C pipes too?
Title: Re: Air Con concerns
Post by: GTVeloce on November 26, 2020, 10:45:43 AM
Interesting idea to use dynamat for that purpose. The only issue I see is that in some parts you will want probably more than one layer and often you need to bend it around a tight section - dynamat might be difficult to mould to such tight curves? The 'horrible, black, sticky stuff' does well at getting into crevasses. Otherwise it may well work. If you have ever tried to remove dynamat from a surface it is just as bad as the 'horrible, black, sticky stuff'...

I wonder what new cars are using for this purpose? Although they usually seem to have the pipes exiting directly out to the engine bay so condensation is not an issue and they use quite a different design for TX valve etc so maybe they don't need any?