Heater part 2: Heater valve 1493.54.709 and control cable 1488.31.723

Last installment we looked at the heat exchanger box itself, this time I’ll focus on the bits that hook it up and control the incoming hot water: the heater valve and the push/pull cable that controls the valve.  The first generation of Sprint’s had a heater valve (1483.54.711) that looked not far removed from a garden tap and you actually had to pop the hood and get out to turn on the flow of hot water to the heater core (if you didn’t realize you were going to want heat before you started out).  At some point this was deemed a little old fashioned so a cable operated valve was put to use -cousins of which can be found on Alfa’s for many years to follow.

Valve failure mode(s): hardening of rubber diverter seal, oxidation leading to through pits or breakage, loss.

Control cable failure mode(s): still/difficult operation, cable breakage/cut leading to too short, loss.

The current state of the parts supply has:

1493.54.709 with new diaphragm seal installed.  Like all rubber things, it just got hard and cracked after 50+ years.  The inner plateau seals against the port in the valve body, keeping the water out of the core when not wanted, the outer ring seals to the body to keep it from leaking when it’s open.

Sort of like this I suppose.  By way of caution, if you are cruising around in your 58 Sprint and have the original valve still in service, you might want to replace the diaphragm.  If it was to suddenly fail you would have a nice fluid loss and overheat if you weren’t paying attention.  You could always take the heater valve out of the loop to limp home I suppose.

This is the original assembly.  Same idea as the currently available item, but physically different.  These countersunk slotted screws and externally toothed washers are original.

This is what actuates the valve -the angled slot in the brass shaft.  You pull the cable out about a few centimeters and a half and the lever translates the motion to rotation that pulls the flat portion of the diaphragm away from a port on the heater body letting water through to circulate through the core.  If installed correctly the spring goes over center in both directions, helping keep the valve both open and closed.

The big post in the foreground captures the outer part of the cable.  The inner part of the cable goes through the cylinder at the end of the lever.  Here’s a good view of the installed spring.  You only install 2 screws at this point since two of them have to go through the bracket on the firewall.

A main failure mode for these is the inlet and outlet tubes corrode and either leak from through holes or break off entirely.  One could machine the old valve to accept a pressed in length of aluminum tubing, but a replacement valve is not too expensive.

Here’s the current replacement item.  Note the extra mounting flanges etc.  I had to combine one of these with an original valve on a Spider I was working on as I couldn’t get the control cable, hoses and mounting bracket to all easily line up.

This T for temperature knob is in pretty good shape.  I don’t think anyone reproduces these yet.  Good thing they live under the dash and don’t heat-cycle and crack as readily as the other control knobs.

Whoever took this car apart cut the cable at the firewall -not leaving enough end to reach the valve -even after cutting about 15mm off the sheath.  The wire is hardened steel -a lot like guitar strings, and they insert it through a hole in the end of the slider then through the little access hole abut 5mm from the tip of the slider they peen it out of round so it wont come out, then they peen the end of the slider onto it too.  Was difficult to drill through the little hole since the bit wanted to deflect off the wire and eat into the slider, but I managed to remove enough material from the end of the wire that it slid out.  A replacement length of wire came from a spare choke cable I had laying around.  I’ll order some wire from McMaster soon.

You can see it installed here.  Do yourself a favor and install the valve and control cable at the same time!  Picture is of a dry run test fit of the 1750 and headers in the engine compartment.  It all fits perfect with the Centerline engine mounts and headers.  I’ll cut the excess cable and make the cute little square bend they did at the factory after I know it wont be coming out any time soon for any reason.

Next up I’ll look at the air flapper control cable and some other parts in this assembly.

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One thought on “Heater part 2: Heater valve 1493.54.709 and control cable 1488.31.723

  1. Hey, the Sprint is looking really good! I wish you had done the heater valve writeup earlier, so I wouldn’t have to discover all that stuff on my own. Good job, Matt.

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