Cab heat temp is low at low engine rpm

[erniet]

My 2004 39' Meridian engine cab heater's temp drops when the engine rpm drops. Once engine is up to operating temp and being driven down the road, the heat temperature is fine. But after a few seconds of low rpm, small towns - slow driving or extended long stop lights the temp output drops significantly. Is this normal? Can anything be done to keep the temperature higher. I understand about the engine's water pump output being lower at low engine rpm. Thanks for your comments.

[gjw319]

Originally Posted by erniet

My 2004 39' Meridian engine cab heater's temp drops when the engine rpm drops. Once engine is up to operating temp and being driven down the road, the heat temperature is fine. But after a few seconds of low rpm, small towns - slow driving or extended long stop lights the temp output drops significantly. Is this normal? Can anything be done to keep the temperature higher. I understand about the engine's water pump output being lower at low engine rpm. Thanks for your comments.

The first thing Iwould change is the thermostat .Because it seems it is staying open to long .It is a cheap fix any way and that causes a lot of headaches.

[Brockx]

Originally Posted by erniet

My 2004 39' Meridian engine cab heater's temp drops when the engine rpm drops. Once engine is up to operating temp and being driven down the road, the heat temperature is fine. But after a few seconds of low rpm, small towns - slow driving or extended long stop lights the temp output drops significantly. Is this normal? Can anything be done to keep the temperature higher. I understand about the engine's water pump output being lower at low engine rpm. Thanks for your comments.

Does the engine temp drop on the gauge? If yes it may be a bad thermostat.

Could also be a low water condition in the engine. Start it cold with the radiator cap loose when you start getting heat from the heater check water level in the radiator add as needed. Tighten cap add appropriate amount to overflow tank. Be sure that cap is loose or off, don't get burnt .

[Triker56]

That is why diesel engines have in their manual.
To not idle for long periods. As the engine will not keep warm enough to keep all the fuel burnt up.

So yes it is normal for heater temp output to drop significantly when at a idle or slow driving.
And with a DP, the water pump has to pump it a long ways before the heater core gets it.

[1ciderdog]

My 2004 Journey would be quite similar to your 2004 Meridian. I have not noticed a heater temperature drop when going slow. I'd tend to think one of the thermostats is not closing as it should.
Bob