logo

The most responsive used parts resource for the 240 Series



... by name, part
number or model
Back to Main Website
Picture of part of a car
Contact us with any questions
    
Tech Article

Volvo 240 Heater Valve Technical Analysis

Last Updated: 11/24/2018
   
Parts Group: Heater valve
This article discusses the Volvo 240 heater valve (a.k.a. heater control valve), for the Volvo 240 Series (Volvo Turbo, 242, 244, 245) with the main focus being on the models through 1991. If you're not here for the technical analysis but would rather buy a used unit from us, guaranteed to work and fit, then please select the link below.
"Ranco Type H" is engraved on each of the three examples I analyzed.

The information herein is based on my 1991 car and used parts that I’ve bought from various used-parts sources. I haven’t verified this personally, but several forums and websites indicate that 1992 and 1993 cars use a different style heater valve. Several of them also mention that this part is no longer available from Volvo.

At least two vendors offer a non-original alternative, but as far as I can tell, one of these requires custom hoses and the other required some sawing or grinding. Nothing wrong with that, but some folks really want to keep their Volvos original.

Napa offers a rebuild kit too, for less than $10 though it was difficult to finally get it ordered, and when it finally arrived, my tech and I weren't convinced that this addressed the likely cause for the type of failure we were concerned about.





On Volvo 240 cars, the control to turn the heater on or off, or somewhere in between, is a simple left-to-right slide on the center console control panel, with some blue paint towards the left and some red paint towards the right — nice and simple.



By contrast, my contemporary BMW 6-series is a much-more-cool car — literally. It comes with a thermostatically controlled heater mechanism. This failed many years ago, and so now to turn the heater on, I have to open the hood and unplug an electrical wire from the heater valve unit. To turn the heater off, I have to open the hood and plug the electrical wire back into the heater valve unit. As the years go by, I more and more wish my BMW were more like my Volvo 240 is. (Yes, those are Volvo seats in the BMW. I transpanted them … another example of what I mean).

However, there IS a problem with my 1991 Volvo 240 Wagon. Its heater is ALWAYS on, regardless of the position of the heater control lever. Being a Volvo, it has a very, very good heater. I live in the Nevada desert, and I owned & drove the car all summer long. I became a not-so-big fan of the heater always being on. I just tested the output today. Even with the outside air being in the 30s (and yes, I mean Fahrenheit, since it’s now November here) it was putting out toasty-warm air into the cabin: 120 degrees.



I’ve been methodically analyzing this part.

I’ve bought three used heater valves off various junkyard Volvo 240 cars. I then hooked them to a test mechanism that I contrived, and concluded that one valve worked fine, one didn’t work and one was sort of in the middle.

The test basically exposed the inlet side of the heater valve to a stream of high-pressure water, and if I could still manually close the valve by actuating its lever, the valve was working correctly — otherwise not.



Above is a picture of the complete heater valve unit with the cable, sleeve and a water hose attached.

A correctly functioning valve cuts off the water flow through the heat exchanger that’s in the bottom center of the front console, far forward, near the firewall, inside the passenger compartment.

On Volvo 240 cars, the internal fan that circulates cabin air is ALWAYS on (even in the fan-is-off position). And so, cabin air is constantly flowing past the heat exchanger. If hot water is also flowing through heat exchanger, this heats up the cabin air flowing by.

That’s why the heater valve is so critical. If it does not close, then hot water will flow, and the cabin air will be heated up.

It’s typical of a Volvo that even when this part fails, it fails on the side of safety, meaning then you’re driving a car with the heater always on, instead of the heater always being off. Volvos are made in Sweden, and are popular in that market. Sweden gets bitterly cold in the winter.



The above image is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license and is made available via Wikipedia by Larske

Its northernmost city, Kiruna, is 90 miles north of the arctic circle, and in only 5 of the 12 months of the year is the average daily temperature above freezing. It’s been known to get as cold as minus 46 degrees there — and that’s without any wind chill factored in. So, if you lived there, would you want your Volvo heater to fail in an always-on or always-off position? Volvo engineers chose “always-on.”

Today, my assistant and I analyzed these three heater valves units in more detail:



The unit consists of:
  • A hot-water pipe with an inlet side and, at a right angle, an outlet side
  • A valve that closes the inlet side off from the outlet side to a total extent, zero extent or somewhere in between.
  • An internal riser that can move a short distance up or down, inside the hot-water pipe.

    • If its top edge protrudes as much as possible from the hot water pipe, then the valve is all the way closed.
    • If its top edge protrudes as little as possible from the hot water pipe, then the valve is all the way open.
    • And, an in-between position means a semi-open valve.

  • A mechanism that attaches to the heater control cable on the center console of the car. The cable performs both a "push" and a "pull" function.
  • When the cable is pulled away from the valve, or pushed towards it, it pulls or pushes a lever that rotates a shaft. Attached to the lever is a spring, probably to help the “push” function along.
  • When the lever on the center console is moved to the right, then the cable is pulled away from the heater valve unit, and when that happens, the internal riser goes down, so that its top edge protrudes as little as possible from the hot water pipe, and then the valve is all the way open.
  • When the lever on the center console is moved to the left, then the cable is pushed towards the heater valve unit, and when that happens, the internal riser goes up, so that its top edge protrudes as much as possible from the hot water pipe, and then the valve is all the way closed.
  • An adjustment mechanism with a screw that has a Torx T15 head. Turning the screw in or out controls how far open or closed the valve is, relative to the position of the lever. Presumably this is intended to compensate for gradual wear in the valve, over the years.
  • A mechanism that provides a sealed copper tube with pressurized air inside. Proper name: capillary tube. This extends from the heater valve through a grommet into a small rectangular plate around which the tube is coiled maybe half a dozen times. The coil is intended to be in the direct path of the hot air flow from the heat exchanger towards the passenger compartment. When the flowing cabin air gets too hot, this mechanism basically cools things down again as a safety feature. Here’s how it works:

    • The hotter the flowing cabin air gets,
    • the more the copper coil heats up,
    • the more the air inside the coil heats up,
    • the more the air pressure inside the coil increases,
    • the more the air pressure pushes against the gray plunger in the unit,
    • the more the gray plunger extends from its brass tube,
    • the more the internal riser is pushed up,
    • the more its top edge protrudes from the hot water pipe,
    • the more the valve gets closed,
    • the more the hot water flow through the heat exchanger is reduced,
    • The colder the flowing cabin air gets.
Brilliant! And, it’s all mechanical ... no electricity needed.

The internal mechanism with the gray plunger of the safety mechanism extending from its brass tube. The Torx adjustment screw is at the top center, just above the plunger, in this picture

The internal mechanism with the gray plunger of the safety mechanism extending from its brass tube. The Torx adjustment screw is at the top center, just above the plunger, in this picture

We had fun testing the safety mechanism by heating up the coil and observing how it closes the valve to some extent. We used a hair drier, very hot tap water, and some other ways that make a safety Nazi really mad.

My guess is that malfunctioning heater valves aren’t so much broken as they need their valve readjusted, so one twist of the Torx screw and you might have fixed the problem on your Volvo too. For some, it might be worth trying. That way, you don’t have to deal with the messy job of removing and replacing the heater valve. Then again, perhaps the inside of the heater valve has deteriorated and the part really does need replacement.

If your Volvo 240 heater valve really, really is dead, and you want to keep it original, then yes, we do sell used units, guaranteed to work and fit.
style element



240SeriesParts.com, a Division of OCLES, Inc. (C) 2003 - 2020 All Rights Reserved.

OCLES is an acronym for Old Car Life Extension Systems … enabling older cars to live longer!