Alfetta Heater Control Valve Rebuild, Part 1 - Alfa Romeo Bulletin Board & Forums

 
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post #1 of 5 (permalink) Old 01-30-2016, 12:22 PM Thread Starter
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Alfetta Heater Control Valve Rebuild, Part 1

The heater control valve for the Alfetta has been NLA for a while now. This valve is used on all of the Alfettas without air conditioning. It may be used on the air conditioned Alfettas and non- A/C GTV6s; it is definitely not used on the air conditioned GTV6s.

This valve is similar to the one used on the 105/115 cars, except that it has the clamp for the control cable molded into the upper housing. To repair the Alfetta valve, one could buy a 105/115 valve (these are available), drill out the rivets, remove the diaphragm, install the diaphragm in your Alfetta housing, and screw (or rivet, but screws are better) the 2 halves of the Alfetta housing back together.

Fearing that the 105/115 valves would also become NLA, I worked on another solution a couple of years ago. The 35 year old valve on my Alfetta was no longer keeping hot water from flowing into the heater core, but it was not leaking water into the passenger footwell, like the original valve was when I replaced it around 1981.

The first photo shows the rebuilt Alfetta valve. The second photo shows the old diaphragm that was no longer sealing properly when closed. The 3rd and 4th photos show the parts I used to repair my valve. The Dorman part is actually a brake master cylinder part that I modified to replace the damaged diaphragm. Since it is not going to be attacked by brake fluid, I figured it would not be attacked by glycol in coolant.

The 5th photo shows the Dorman part before modification.
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Tom Henneka
75 Alfetta GT (Original owner), 92 164S
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post #2 of 5 (permalink) Old 01-30-2016, 12:28 PM Thread Starter
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Alfetta Heater Control Valve Rebuild, Part 2

To reduce the OD of the Dorman part, I cut it with scissors along the outside of the middle rib. The 6th photo shows this modification. Because the Dorman part’s rubber is thinner than the OE diaphragm, I glued (with Pliobond) a 1mm thick rubber washer onto the center of the Dorman part (see the 7th photo). This washer is on the side of the diaphragm that is not exposed to coolant. Gluing on this washer also seals the very tiny vent that is near the center of the Dorman part.

The 8th photo shows the new diaphragm positioned in the upper housing. Since the rubber is thinner, I place a large O-ring in the groove in the lower housing (see 9th photo) to seal in the coolant.

I screwed the 2 halves of the housing back together with 4-40 screws and nuts. You originality nutcases might want to rivet the halves back together, but screws let you more precisely control the clamping force.

The repaired valve has been on my car for a couple of years. I also repaired my second valve and put it on the shelf.
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Tom Henneka
75 Alfetta GT (Original owner), 92 164S
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post #3 of 5 (permalink) Old 01-30-2016, 04:05 PM
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Nice work. For mine, I was able to buy a replacement Diaphram from Scott's old rubber Co.
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post #4 of 5 (permalink) Old 02-01-2016, 05:05 PM
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I have a feeling that older Giulia valves use the same diaphragm, which is available new:
https://www.centerlinealfa.com/store/2783

So how does it work, did you test it on the car? I'm asking because a new valve I bought from Italy opens a bit too much...

1975 Alfetta; ex 1973 Spider; ex 1984 Alfetta Quadrifoglio Oro
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post #5 of 5 (permalink) Old 02-01-2016, 05:10 PM
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I like this fix. The pride of being resourceful goes so much farther than buying something off the shelf and installing. Great work.

Brian __________________________________
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