Heat not hot enough on '92 Jetta Eco...

[larry104]

Anybody have the heat not work well on an A2 Jetta? What'd you do to fix it? The coolant is full, the thermostat is good, and the engine reaches proper operating temperature (between 1/2 and just under 3/4 on the gauge). The cooling fan kicks in at just below 3/4 and runs until it reaches 1/2. I'm thinking it's the blend door. The cooling system is clean, so I don't think it's a plugged heater core. Anybody?

[jtanguay]

sounds like the blend door.  there should be a valve to send the hot coolant through the heater core.  check the temp of the coolant lines going to the heater core when the motor reaches operating temp.

could be a clogged heater core though...

[burn_your_money]

MK2s don't have valves to allow coolant through the heatercore, it is always flowing through it. Only mk1s have the valve. It might be the foam inside the heater box that is used to control the hot/cold. One sure fire way to check is when the engine is getting warm (but not hot) grab each line going to the heatercore, they should both be the same temperature. If you try the check when the engine is fully hot they will both be the same temperature because of heat transfer through the coolant.

[MikkiJayne]

Have you got the heater core bypass valve installed? One of the valves on my Corrado failed and stopped most of the flow through the heater core. I took it out and it works again - just got to watch the core doesn't pop!

Mikki x

[jtanguay]

MK2s don't have valves to allow coolant through the heatercore, it is always flowing through it. Only mk1s have the valve. It might be the foam inside the heater box that is used to control the hot/cold. One sure fire way to check is when the engine is getting warm (but not hot) grab each line going to the heatercore, they should both be the same temperature. If you try the check when the engine is fully hot they will both be the same temperature because of heat transfer through the coolant.

hmmm i thought mk2's had it... guess not

[bevboyy]

Get your cooling system flushed.

[larry104]

Well, there was nothing wrong with the heater, except bad design. The heater core flow is always on, as was pointed out above. Inside the heater box are vacuum-actuated doors to control defrost, floor, and vent. A cable operates the blend door, which diverts outside air to the heater core.

The blend door is perforated with several large holes. These holes don't let enough outside air pass over the heater core when the temp control is slid to "hot."  I cut a sheet of thin aluminum and drilled it and the blend door for sheet metal screws (no fun). I covered all but the four small holes in the blend door top and bottom. I put it back together and, wow, HEAT!  The A/C still works fine. No problems.

To get to the door, you must remove the center console, knee bar, the center vent (2 lock tabs on the lower surface, 2 phillips head screws in the top surface), and the manifold that connects to the center and defrost vents (What a PITA).

While apart, I replaced the old foam gasket on the manifold with 3/8 in. wide self-adhesive weather stripping. I used the same stuff to fix the leaky center vent shut offs. No more whistling, and they actually work.

Ready for winter.

[rabbitman]

Hey I got a question. I think I figured out that my '82 rabbit has an old style heater core housing from a 1977-80 in it. Actually I just remembered mine has the vents in the dash below the radio but there is no air duct going to it, there isn't even an opening in the heater box to hook a duct. The only heater options are floor and defrost but the inside of the car never gets comfortable (unless your wearing carharts, fur hat and gloves ). I went through last winter with a pitiful heater and I'm not looking forword to doing it again. :roll: thanks guys