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Passat with no heat in cab


volkswagon

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iThanks for the added info. A heater is a heater is a heater... the components are all similar & none of it rocket science. Let's try to eliminate the easy stuff before taking things apart. If the engine warms up properly then the coolant has enough heat. The vents blow air so the suction & bird case (I mean "dizzy mouse cage") are not likely problems. Locate the heater hoses under the hood... can you put your hand on them? After warmed up, is one hotter than the other? Is there a control valve in the hose like some vehicles? If there is a control valve, does it move when you change the controls? If nothing external can be found... then likely the blend door.

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  • 2 weeks later...

Thanks, I went there and got some good help. Now I have excellent heat when driving or when the car is parked but idling at or above 1200 rpm. Any time rpm drop below 1200 I can feel a drop in temp, even tho my SGII shows no drop in coolant temp.:shrug:

Did you search on the VW forum? http://forums.tdiclub.com/ This is by far the best forum as far as technical info goes I have ever seen on the web, tons of info and lots of help. I go here whenever I need VW help on my 03 TDI. I have never been let down yet.

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  • 5 months later...

I would look at the Temp control on the heater hose, it is perhaps not functioning properly. It could be Vacuum controled or cable or even electric, just not sure. But since you lose heat when idleing, it would point to either, low vacuum, or electrical current not allowing the valve to stay open. Could also possible be a stuck thermostat, or clogged passages in the heater core or Radiator or both. Also when was the last time your Coolant was changed? If your PH is off it may have caused an issue the impeller on the water pump to erode so that it is not moving enough water at idle, or other internal damage.Could also be heater fan not getting enough current at idle, or one of the air intakes is blocked with leaves or similar.In any event if it works at speed but not at idle, it has to be close to something I mentioned. No heat= no/low coolant flow or low air flow over the core.

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I'd question the water pump.. Mk4s (factory WP) used a composite impeller. Most aftermarket units (i.e. from www.germanautoparts.com) have the steel impellers. The composite one are known to separate from the shaft and not spin at full bore, often eventually crumbling to bits and then you've got bigger problems. when was the last WP/tbelt swap?

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I bought this: http://www.ross-tech.com/***-com/index.html a few years ago for our Passat. Cost about $120 after an upgrade and it is amazing how much info it will give you. I think I paid around $50 for the basic software and the interface on ebay and another $70 from ross-tech for the upgrade. I scan it sometimes just to see what is going on and there is usually a soft code for some kind of heat/ac issue. Blend door fault if I remember right.

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I'd question the water pump.. Mk4s (factory WP) used a composite impeller. Most aftermarket units (i.e. from www.germanautoparts.com) have the steel impellers. The composite one are known to separate from the shaft and not spin at full bore, often eventually crumbling to bits and then you've got bigger problems. when was the last WP/tbelt swap?

I think it's coming due shortly. When I bought the car last August I checked into that and it had been done at the correct time. I will sure check into it.
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