Heater Control Valve HCV
Discussion
Hi,
As can be seen in this photo my Precat Griff HCV is missing its motor, that's not the issue.
Done a lot of searching but still have some questions.
From the photo can anybody say which position the lever on the VW valve should be for 'heat off', up or down towards the battery? Mine doesn't seem to make any difference so maybe the valve is not working anyway.
Between the HCV and the heater matrix I have the bypass hose, not fitted to all cars. Please try and explain how the bypass in its present position prevents hot coolant getting to the heater matrix when a working correctly HCV is shut, because I don't get it.
I have yet to determine which hose in the photo, top or bottom, the coolant flows and returns BTW.
Cheers
As can be seen in this photo my Precat Griff HCV is missing its motor, that's not the issue.
Done a lot of searching but still have some questions.
From the photo can anybody say which position the lever on the VW valve should be for 'heat off', up or down towards the battery? Mine doesn't seem to make any difference so maybe the valve is not working anyway.
Between the HCV and the heater matrix I have the bypass hose, not fitted to all cars. Please try and explain how the bypass in its present position prevents hot coolant getting to the heater matrix when a working correctly HCV is shut, because I don't get it.
I have yet to determine which hose in the photo, top or bottom, the coolant flows and returns BTW.
Cheers
In order to say which position is hot and which is cold I would have to crawl down the footwell and do an experiment. I don’t mind doing that, but it won’t be tonight.
Remember it won’t make an instant difference. You are controlling the flow of water and air constantly blows across the matrix. If it is hot and you close the valve you won’t notice a reduction in temperature until the air has cooled the water in the matrix. Most modern cars work the other way round. I.e. water flows through the matrix all the time but the heater controller diverts air around the matrix for cold or through it for hot. Therefore the temperature change is much quicker (instant in comparison).
If the valve is closed then that stops water flowing through the matrix and it is forced through the bypass.
I am not sure it matters which way the water flows, I.e whether the control valve is on the supply or return. Again, I could carry out an experience but these pipes have been replaced on my car and I am not sure whether or not they are the same way round as they originally were.
Let me know if you want me to tell you which way round the lever goes when operating the switch.
Remember it won’t make an instant difference. You are controlling the flow of water and air constantly blows across the matrix. If it is hot and you close the valve you won’t notice a reduction in temperature until the air has cooled the water in the matrix. Most modern cars work the other way round. I.e. water flows through the matrix all the time but the heater controller diverts air around the matrix for cold or through it for hot. Therefore the temperature change is much quicker (instant in comparison).
If the valve is closed then that stops water flowing through the matrix and it is forced through the bypass.
I am not sure it matters which way the water flows, I.e whether the control valve is on the supply or return. Again, I could carry out an experience but these pipes have been replaced on my car and I am not sure whether or not they are the same way round as they originally were.
Let me know if you want me to tell you which way round the lever goes when operating the switch.
My valve is mounted the other way round to yours, i.e. the lever is in front of it, not behind. (It is also mounted the other way up so the lever points down).
Anyway, on mine, pressing the cold button turns the lever clock wise. Hot, anticlockwise. As your valve is the other way round, then I would expect these to be reversed.
I hope that this helps.
Anyway, on mine, pressing the cold button turns the lever clock wise. Hot, anticlockwise. As your valve is the other way round, then I would expect these to be reversed.
I hope that this helps.
Good of you to do some delving.
I think i've found a photo of how the complete assembly should look and gather from your message that this is how yours looks
when viewed from the passenger seat with the gubbins controlling it above nearest the scuttle. If so then on yours when the shinny
lever is down the valve is in the closed and cold position ..........yes?
Regarding the bypass in the pipe maybe mine is in the wrong place and should should be between the HCV and flow from the engine, then what you say would work.
"If the valve is closed then that stops water flowing through the matrix and it is forced through the bypass"
Because having the bypass between the HCV and the matrix means that regardless of the position of the HCV hot coolant will never be diverted back to the engine.
Anyway thanks for the help, my objective is to make the cockpit cooler so I might rig up a simple/discrete hot/cold control somewhere.
Cheers
I think i've found a photo of how the complete assembly should look and gather from your message that this is how yours looks
when viewed from the passenger seat with the gubbins controlling it above nearest the scuttle. If so then on yours when the shinny
lever is down the valve is in the closed and cold position ..........yes?
Regarding the bypass in the pipe maybe mine is in the wrong place and should should be between the HCV and flow from the engine, then what you say would work.
"If the valve is closed then that stops water flowing through the matrix and it is forced through the bypass"
Because having the bypass between the HCV and the matrix means that regardless of the position of the HCV hot coolant will never be diverted back to the engine.
Anyway thanks for the help, my objective is to make the cockpit cooler so I might rig up a simple/discrete hot/cold control somewhere.
Cheers
lancepar said:
my objective is to make the cockpit cooler so I might rig up a simple/discrete hot/cold control somewhere.
I had a manual 'override' fitted on my precat by tvrssw. Uses a sort of choke type cable with the handle in the glove box. Cost a few pounds and about 30 mins labour. Works perfectly.Chris
Yes, that picture is how mine looks.
The by-pass on your picture looks to be correct, i.e. between the engine and the control valve.
Edited to add, in your text you are saying that the bypass is between the control valve and the matrix.
In the photos, the by pass is in front of the control valve, i.e. between the control; valve and the engine. This is what I would expect, but if I have got it wrong, do say.
The by-pass on your picture looks to be correct, i.e. between the engine and the control valve.
Edited to add, in your text you are saying that the bypass is between the control valve and the matrix.
In the photos, the by pass is in front of the control valve, i.e. between the control; valve and the engine. This is what I would expect, but if I have got it wrong, do say.
Edited by BIG DUNC on Tuesday 9th July 23:04
chj said:
I had a manual 'override' fitted on my precat by tvrssw. Uses a sort of choke type cable with the handle in the glove box. Cost a few pounds and about 30 mins labour. Works perfectly.
Chris
Sounds like a plan Chris, like it, any links?Chris
Cheers
BIG DUNC said:
Yes, that picture is how mine looks.
The by-pass on your picture looks to be correct, i.e. between the engine and the control valve.
Edited to add, in your text you are saying that the bypass is between the control valve and the matrix.
In the photos, the by pass is in front of the control valve, i.e. between the control; valve and the engine. This is what I would expect, but if I have got it wrong, do say.
Duncan,The by-pass on your picture looks to be correct, i.e. between the engine and the control valve.
Edited to add, in your text you are saying that the bypass is between the control valve and the matrix.
In the photos, the by pass is in front of the control valve, i.e. between the control; valve and the engine. This is what I would expect, but if I have got it wrong, do say.
Here is another photo which shows how mine must have been once upon a time.
In this and on my car the bypass connecting the top and bottom hose is between the HCV and the matrix, that's why I don't understand how coolant is prevented from circulating round the heater box matrix.
Lance
lancepar said:
chj said:
I had a manual 'override' fitted on my precat by tvrssw. Uses a sort of choke type cable with the handle in the glove box. Cost a few pounds and about 30 mins labour. Works perfectly.
Chris
Sounds like a plan Chris, like it, any links?Chris
Cheers
I've been in touch with tvrssw and received a message stating "they have never done a conversion so not sure which parts are required" so that's a dead end then.
Last visit to Central I picked up a manual HCV and viewed the precats they are working on and they all had the HCV in the flow from the engine, then the bypass between the two pipes before the matrix.
Last visit to Central I picked up a manual HCV and viewed the precats they are working on and they all had the HCV in the flow from the engine, then the bypass between the two pipes before the matrix.
I've seen this photo, thanks but what it doesn't indicate is the order of components conected to it.
For example, is it from the LH, engine (flow),HCV,bypass,Matrix,then return via the top pipe to the engine, which would be as supplied in the Precat Griffs?
The photos in the thread show how it was originally, but it is difficult to understand how it worked in practice, this is the confusing thing.
For example, is it from the LH, engine (flow),HCV,bypass,Matrix,then return via the top pipe to the engine, which would be as supplied in the Precat Griffs?
The photos in the thread show how it was originally, but it is difficult to understand how it worked in practice, this is the confusing thing.
Hi Ian,
It's just that if the HCV is turned off and is in the supply it cuts off the flow so the coolant can't reach the bypass junction anyway. I just don't understand how hot coolant is prevented from circulating round the matrix and also how the bypass comes into play.
I'll try and draw a diagram and post it on here.
Cheers
Lance
It's just that if the HCV is turned off and is in the supply it cuts off the flow so the coolant can't reach the bypass junction anyway. I just don't understand how hot coolant is prevented from circulating round the matrix and also how the bypass comes into play.
I'll try and draw a diagram and post it on here.
Cheers
Lance
Apologies to all who have been trying to put me straight about this.
At Central today on the floor was a precat heater box with the HCV and pipes attached so now the penny has finally dropped.
I hadn't grasped that the flow and return pipes were via the white ninety degree fittings and not as i thought
It all makes perfect sense now.
Ian,
Yes can do but........
If you right click on the photo a drop down menu will appear then click Save Image On then a Save Image window will appear and you can save it on your Desk top or in your Griff pictures. Simples.
If it don't work send me a PM. (and you can delete your email address from prying eyes).
Lance
Yes can do but........
If you right click on the photo a drop down menu will appear then click Save Image On then a Save Image window will appear and you can save it on your Desk top or in your Griff pictures. Simples.
If it don't work send me a PM. (and you can delete your email address from prying eyes).
Lance
Edited by lancepar on Saturday 20th July 15:02
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