No interior heater function during low engine revs.

[Alex]

The heater only produces interior heating when the engine revs are high.
Any ideas as to why there is no heat during low revs even if the fan is still running well - or is this normal for E36 BMW's?

[DG888]

bmw heaters' uses the water from the engine to heat the air... the heater should produce heated air once the engine has reached its normal operating temperature (regardless of engine rev)..

[tonysticks]

I recall that I've faced this problem Alex. I had to keep driving my car fast when it's cold outside to keep the blower air hot. When I had to stop at a traffic light for instance, the air will become very cold and I had to turn the heating off until the traffic light turns green . There are three possible reasons for this problem AFAIK:

1. The coolant inside your radiator is low. Check that and make sure it's on the maximum level allowed.
2. Your thermostat is busted and needs to be replaced. Does your engine temperature reach to 12 o'clock? If not, then here you go...
3. Your heater hoses need cleaning. I didn't try to clean them myself, but it was very easy (as I recall).

Good luck.

[bmdubsalot]

My heater isnt working so well either. I have a 97 318i. The entire cc unit turns on and off randomly while the car is warming up from a cold start. It seems to work fine once the engine is at normal running temp though. Ideas?

[P.Lavers]

I have this same problem on my 320i, my engine will be fully at the 12 o'clock and when I'm idling it will blow luke warm to cold air. This is a major problem seeing how I am in Germany and its about to get VERY COLD! I was very low on coolant and I filled it up fixed the low idle lol, but its still blowing luke warm air. So is there a DIY on how to clean out the hoses I think thats my next problem. Does old or bad sparkplugs have anything to do with that??? Thanks!