240 Heater valve. How does it work?

hrforever · Post by **hrforever** » 05 May 2009, 01:16

Ok, just a little back ground to this question. A couple of months ago the heater water valve started to leak and so I went and bought an after market tap and installed this, using the original slide controller cable to achieved full on and off. Unfortunately, the heater now blows either hot or cold air and I am unable to regulate the temperature.

When doing the change over I cut the copper tube that goes into the heater body as I figured the tap would do the job, but prehaps I was wrong.

So my question is, how does the Volvo valve work and what roll does the copper tube play. Does it have its own thermostat adjustment to control the temperature. For the life of me I have never seen such a complicated unit and I cannot work out why the aftermarket tap would no regulate the temp.

Any assistance appreciated.

hrforever · Post by **hrforever** » 06 May 2009, 06:11

Doesn't anybody have an answer?

There are numerous references throughout this forum about the replacement of the valves but nothing about how they work. Surely someone has investigated their operation and knows how they work and how to set them for best operation.

Anyone???????????

Post by **vegasjetskier** » 06 May 2009, 09:26

I'm not familiar with the 240, but the cars I am familiar with let the coolant full-flow into the core, then control the temperature by mixing the hot air from the core with cooler air from outside or cabin air using a damper in the heater housing. Maybe the copper tube you cut controls a damper inside the housing. I can post up some parts diagrams if you give me the year and engine your car has and climate control unit name if you have it.

Post by **billofdurham** » 06 May 2009, 11:57

Was the after market tap a replacement for the heater control valve or was it something that you were intending to modify?

There are two types of valve for the 240 but one is specifically for the automatic system and has a probe which sits in the heater body to help regulate the heat. The other type has no probe but both work roughly as vegasjetskier said. I think, however, that the valve regulates the flow of water rather than letting it in at full-flow - the hotter you want the more water pours in and vice versa until no heat and no hot water enters the system.

What you describe would appear to be an on/off tap which wouldn't regulate the flow.

Bill.

hrforever · Post by **hrforever** » 08 May 2009, 19:53

Thanks for the responses. As for the taps/valves they both appear to be on/off with the degree of opening being controlled by the simple slide lever on the heater panel. This is not an auto climate control heater.

The original valve simply has a copper probe that goes into the body of the heater fan unit and it does not connect/adjust any other part of the heater apart from something in the valve itself.

My question is what does the probe do and what does it adjust on the valve and why wouldn't a simpler on/off slide valve do the same thing?

Post by **vegasjetskier** » 08 May 2009, 20:23

hrforever wrote:Thanks for the responses. As for the taps/valves they both appear to be on/off with the degree of opening being controlled by the simple slide lever on the heater panel. This is not an auto climate control heater.

The original valve simply has a copper probe that goes into the body of the heater fan unit and it does not connect/adjust any other part of the heater apart from something in the valve itself.

My question is what does the probe do and what does it adjust on the valve and why wouldn't a simpler on/off slide valve do the same thing?

It sounds like a thermostat bulb-and-capillary system. The bulb and capillary tube contain a liquid that expands when the temperature in the heater housing rises. The expanding liquid then controls the flow of coolant through the valve, limiting the temperature in the heater. It would help to keep the heater temperature relatively constant.

Post by **vegasjetskier** » 09 May 2009, 08:50

Here's a shot of the inside of the heater. #7 is the capillary tube heater control.

And here's link to the whole 240 manual online.

The next page in the manual, 53 shows the capillary tube connected to the coolant valve.

Post by **vegasjetskier** » 09 May 2009, 10:47

Here's a whole manual just on the climate unit:

hrforever · Post by **hrforever** » 09 May 2009, 20:24

These manuals show fantastic detail on disassembly and assembly and shows the heater valve and capillary in great detail, but the question still remains, what does the capillary actually do to the operation of the valve?

Having had a good look at a unit outside the car, the capillaries purpose is still a mystery. If it does infact control the flow of water I cannot see how it would adjust the valve through the full range of movement.

Perhaps I'm just loooking for an answer that doesn't need to be asked when all I need to know is why the aftermarket valve does not provide a range of temperatures given the position of the slide control. From doing a search on this forum, this all or nothing heating problem is common but there's no answer as to why.

Post by **vegasjetskier** » 09 May 2009, 21:03

Can you post a pic of the valve you installed?