Only blowing hot [FIXED]

So... Today I changed my car HCV for a new one made by TRW. When I bought it, it had a bypass. Thinking the one he had may be broken, I've put a new one today.
But the problem is, either I change the dial to cold or hot, the car is always blowing hot air inside.

just to add, I tested the voltage at the plug, car engine off with an analogic multimeter. (no idea where the heavens is my digital... when I need them, they go missing)
the voltage either with switch to hot or to cold at the plug that connects to the hcv, was always the same, around 10v or so. (yep I disconnected the plug)

Voltage at the HCV will only ever be vehicle voltage, 12 or so, or 0v.

Temperature is regulated using pulse modulation, ie. solid 12v for cold, long pulses of 12v with bits of 0v for cool, shorter pulses of 12v for hotter and constant 0v for full hot.

So you need to wait to see what you have, not just a case of a measurement straight away.

That said, you should have constant 12v for cold and constant 0v for hot on demand.

If that is not the case then suspect the panel. In the first instance sweep the heat dial back and forwards a few times to clean the potentiometer, if you still have voltage other than the above then its time to replace.

Incidentally analogue meter is far better for this job as you can see the pulse width more easily. As is the driver's side indicator repeater in the wing as that's the same plug and will give you a nice bright visual indication of what is going.

Although first, 10v sounds low. What is battery voltage?

Not sure what's the battery voltage because I haven't measured it.
Tomorrow I'll measure again and will try the trick to switch the dial to cold and hot several times.
Also will see with the engine running.
But I can say, no pulses happened. And the dial on hot was showing positive voltage at the plug.
Even so, if 0 volt is hot, then... Oh, I forgot to mention, the air wasn't scalding hot. It was warm.
So, maybe is the panel screwed up... I love this car, but starting to give too many headaches...

plugged in a digital multimeter.
Engine running, voltage at the plug in the hot, near 14v
voltage in the plug at cold, around 13.60v
in the middle, there was feeble pulses ranging from 13.60 to 13.90v
plugged in the HCV I took out (Ford original, part number is the same as revised versions) there was no momement from the little thing inside the hole.

Oh, I measured the ohm on my old hcv, and at the pins I get a reading of 15-17 (multimeter set to 200)

I suggest you disconnect the connector from The HCV and tape it over. The HCV will then fall back to its default state, which is hot. That'll get you through the winter.

Then, sometime get a replacement potentiometer for the heater panel.

SandStorm said:

[post]358620[/post] I love this car, but starting to give too many headaches.

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You get disheartened pretty easy, it seems? All cars have things going wrong, it's part of the deal of having a car.

Is always on hot, so the winter is OK just weird because with that voltage should be the cold.setting?
Eventually will solve that

Well, sometimes I am impatient xD this year I finished my ford orion project that lasted 6 years to put in top shape, besides also have my daily Fiesta

This weekend gonna have a friend spare me an extra control panel (already with lighter in it instead of the tray, but with 3 setting of air flow)

I believe the problem itself is my panel.
Yesterday I did the bulb trick but no lighting, pulse, whatever.
Who knows, maybe my panel is the reason my air recirculation isn't working either

SandStorm said:

[post]358674[/post] Is always on hot, so the winter is OK just weird because with that voltage should be the cold.setting?

Click to expand...

Yeah, if a HCV is faulty then it can fail in any position, but if it is OK, but with no juice going to it then it's hot. Useful to know because if it hot without the connector, but only lukewarm with it connected and the panel control set on max, then you know it's the panel.

SandStorm said:

[post]358674[/post]
This weekend gonna have a friend spare me an extra control panel (already with lighter in it instead of the tray, but with 3 setting of air flow)

I believe the problem itself is my panel.

Click to expand...

Yep, me too. You can often/sometimes fix that pot. with contact cleaner, but it's hit and miss job. A replacement panel is a better option.

Incidentally - I know this sounds bizarre - check your cabin filter as well, as restricted air flow behind the control panel/radio area causes all sorts of weird problems.

SandStorm said:

voltage at the plug in the hot, near 14v

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Wants a panel - should be zero at hot.

Also sounds like it might want a HCV was as well because with voltage in the plug you would expect to see cold at all times.

I had the same problem on my racing puma. It frustrated me for a while. First I changed the HCV with a genuine ford part. Great disappointment when this didn't work. I then went to the control panel and found the multi-plug wasn't connected, (I guess I should have checked that first), I connected this and it still didn't work. It was at this point I realised the previous owner had obviously been on the same fault finding journey. I replaced the control panel, still no joy so I assumed it must be a wiring or earth fault, especially as the earth wire in the door pillar was missing. I did a final continuity check on the cables before admitting defeat and heading to an auto electrician and everything seemed fine so as a last resort I bought another heater control panel (the 3rd one) for about £15 off eBay after confirming with the seller that it was fully working. Five minute job to fit it, switched the engine on and everything worked including the air conditioning which can't have been switched on for at least a year. Just a shame about the hours and £'s wasted before then).

Fixed, new panel fitted!
Now makes cold and hot.
also... I guess my old HCV was good too. but will be saved for emergency, I wont go change it again for the old HCV.
This new panel have a lighter in, but I didn't connected the lighter wirings. I don't some, and I have the one inside the tray that can power my 4G router, hidden from everyone :lol:
Only my recirculation aint working, but that's the flap stuck. No worries on that. The AC?
I need to try since mine wasn't working before. I'll have lunch and run a bit to see if it goes.
But finally, the important is fixed! Thank you everyone