Heat Goes Away When Car is Stopped - 1990 Legacy

[Don]

In an earlier post I was dealing with a problem where the blower would not
come on. Managed to fix that problem. It was a cold solder joint on the
connector at the back of the dashboard switch unit. So now when the car is
going, warm air is being blown about the car.


Now for the interesting twist. When the car is stopped for a minute or two,
the air being blown out of the heater or defrost vent goes cold. When the
car starts moving again, warm air reappears.So I am thinking one of two
things might be happening:

1) The coolant level is low (or maybe an air bubble) and when the engine is
idling hot water is not making it into the heater box to be blown through
the interior.

2) There is a solenoid or something that cuts off hot water to the heater
coil when the engine goes to idle speed.

Any ideas?

Thanks!

Don

 

[AS]

I agree with your air bubble theory, but it could also be a defective
water pump (worn out impeller), a stuck open thermostat (you would see
the temp gauge go down), and yes, some wehicles have a solenoid valve to
cut the hot water off the heater core.

 

[dnoyeB]

1) The coolant level is low (or maybe an air bubble) and when the engine is
idling hot water is not making it into the heater box to be blown through
the interior.

2) There is a solenoid or something that cuts off hot water to the heater
coil when the engine goes to idle speed.

Any ideas?

Thanks!

Don

most likely #1

 

[Martin C]

Hi Don,

That sounds as if your internal heater pipe is partialy blocked or kinked.
If you only get internal heat when the water pump is causing pressure from
running rpm maybe the circulation is poor and the small amount of water
trickling past can be cooled by the fan - what does your water temp gauge
say ?

I have a 1987 L series and I took out the thermostat, removed the center
device and re-fitted the flat disc with the hole in it, my temp is perfect
in the hot Aus summer now and the disc still restricts the water flow enough
to encourage the water through the internal matrix.

Let me know what you do to fix it

Regards

Martin