Heater Advice

[SteveGriff]

Hi Guys,
When I bought my Griff I was told that the heater temperature adjusts from Hot to Very Hot and all Griffs do this.
This is doing my nut in. Is it the case that no Griff has cool air coming in (without air con)?

I just dont want to start trying to fix it if it wont ever be right.
Cheers!

[The AJP Griff]

Not so at all, its definitely not a case of 'THEY ALL DO THAT' you should never have to put up with it always throwing out hot air. Firstly you need to synchronise the hot water valve so that its definitely closed when your control knob is set to the cold position. There is lots in the archive on how to do this and its pretty straight forward. Sometimes the heater valve servo potentiometer resistance value can be affected by heat transfer thus moving the valve position a little allowing hot coolant to still pass through the matrix without you altering the controls and some people will wire in a switch to isolate the power supply to prevent this.
If your valve is correctly synchronised and also the pot is isolated then the only other cause to still getting hot air is if the valve is worn and passing. They are a cheap VW part from memory and again there should be a lot in the archives on the valve as well

[Hedgehopper]

These may help..

http://www.bertram-hill.co.uk/Pages/grifheater.asp...

http://www.tvr-car-club.co.uk/forum/forum_posts.as...

[SteveGriff]

Thanks for the advice. I will work through checking and setting the water valve/potentiometer.

[SteveGriff]

Hi guys,
Just a update on the heater. I exposed the potentiometer and stepper motor assembly. The cables were cut so I re-made them. Still no joy.
I checked for a 12v supply at the green (common) cable at the pot and it is 0v.
I looked further up into the dash by getting into a position only an expensive pole dancer can do. I could see another stepper motor assembly next to a micro switch attached to the heater box(i think). The cables for this stepper motor and micro switch were also cut. They are cut at the same place and it looks deliberate.

I am planning to move the fusebox assembly to behind the driver seat and think that I will investigate the heater further when I can access the fuses more easily.

[The AJP Griff]

Sometimes people cut the wires because the pots fail and the servo motors run continuously. The one with the microswitch on the side of the heater box is for the flap which controls air up to the screen or down to the footwell.

[SteveGriff]

The AJP Griff said:

Sometimes people cut the wires because the pots fail and the servo motors run continuously. The one with the microswitch on the side of the heater box is for the flap which controls air up to the screen or down to the footwell.

That explains why I dont get much air to demist the windscreen when it is set to "up".

I take it that no upgrade from the standard set up is readily available? The pot idea did seem to me to be simple but not great.

[The AJP Griff]

Whilst its not the very best heating and ventilation system ever built for a car it all works pretty well when set up correctly. Personally I would just change the pots if they are duff and set it up properly and I think you'll be pretty happy with the result. I'm not aware that anyone retails an upgrade but I do know someone that was re-designing a better system but that seemed a lot of hassle to me.

Edited by The AJP Griff on Monday 5th August 16:54

[SteveGriff]

The AJP Griff said:

Whilst its not the very best heating and ventilation system ever built for a car it all works pretty well when set up correctly. Personally I would just change the pots if they are duff and set it up properly and I think you'll be pretty happy with the result. I'm not aware that anyone retails an upgrade but I do know someone that was redesignoing a better system but that seemed a lot of hassle to me.

Fair enough, just thought that given others have experienced similar problems a solution may have cropped up.
I'll measure the ohms on the pot unless anyone knows the spec of them?

[The AJP Griff]

SteveGriff said:

Fair enough, just thought that given others have experienced similar problems a solution may have cropped up.
I'll measure the ohms on the pot unless anyone knows the spec of them?

They should be 10k

[Argent]

The AJP Griff said:

Whilst its not the very best heating and ventilation system ever built for a car it all works pretty well when set up correctly. Personally I would just change the pots if they are duff and set it up properly and I think you'll be pretty happy with the result. I'm not aware that anyone retails an upgrade but I do know someone that was re-designing a better system but that seemed a lot of hassle to me.

Edited by The AJP Griff on Monday 5th August 16:54

Second that, on a 500 you can get good heating for the Winter and reasonable cooling in the Summer when it's all working properly, the real problem with the system is heat soak when driving at low speeds in hot weather.

A.

[TVR Beaver]

On the top valve that switches the water from the engine... You can get at this quite easily by removing the glove box and a bit of pipe going to the LHS air outlet.... I found on mine that the pot as held by one crappy screw had moved a tad... the valve was working but not closing off... I re-positioned the pot, and clamped / glued it in position... job done!.... Now it's nice and cold... but it's put my engine temp up by 5 deg It's amazing how much heat you loose through the heater

[Rob_the_Sparky]

The AJP Griff said:

Whilst its not the very best heating and ventilation system ever built for a car it all works pretty well when set up correctly. Personally I would just change the pots if they are duff and set it up properly and I think you'll be pretty happy with the result. I'm not aware that anyone retails an upgrade but I do know someone that was re-designing a better system but that seemed a lot of hassle to me.

Edited by The AJP Griff on Monday 5th August 16:54

That may be the case but soldering wires to a pot designed to mount on a PCB is horid. Also that the pot can be rotated in its mounting is also horid. Although it works well enough it is poor design, really made me cringe whan I took a close look at what they have done. Not that it needs re-designing exactly, the principle is sound, just putting together in a much more robust manner.

[G5FTH]

Hi Guys,
Just an update...
I re-attached the cables to the stepper motor for the direction control and the temperature control.
Now the stepper motor for temperature runs constantly. I checked the resistance of the pot and its fine. I removed the centre console and checked the ribbon cable connections and the resistance of the pot too and its all ok.
I replaced the 10k pot anyway as I had a spare.
Its still the same, the stepper motor just keeps running. I notice the ribbon cable plugs into a module - could this be the culprit? Any ideas greatly appreciated.

Incidently, since re-attaching the cables the air con switch now operates a stepper motor low down near the battery. I dont have air con and assume its doing nothing important? It does not run continuously and it seems to operate as it should.

Thanks!

[Loubaruch]

If you have attempted to align the temperature servo as per:

http://www.bertram-hill.co.uk/Pages/TVRGriffith.as...

and are sure that all the connections are sound and it still runs continuously then the heater electronics box is a possible cause. Perhaps someone on here has a spare or has the dashboard out and could let you try theirs.

I suspect that the "box" is just an amplifier to increase the operating current from the potentiometer to the servo motor.