Low heat from HVAC
 

Hi gang.


The old 3.0 has decided it doesn't want to pump much heat in the HVAC. Outside temperatures below -15c and I can't get hot air from the face vents even with the temp set to 29c.


This thing used to burn my eyebrows off.


The temp gauge comes up to mid-point as usual (yes, buffered, I know).


Ideas?

The center vents use the mechanical dial. Blue and red dot dial. This site had to teach me change it between hot and cold!

Does the heat valve have any codes when scanned? Do you have a laser thermometer? I would check hose temps to verify hot water is circulating.

The Foxwell scanner will show the heat core temperature.

IR the thermometer to check the coolant temperature also when coolant gets low often times an air bubble will form in the heater, core and kill your cabin heat.

If the fake thermometer on the dash is at noon, it should be plenty hot for cabin usually when the thermostat fails the coolant temperature will be low enough that the needle won’t quite get to the top.

stuck closed heater valve or low coolant or the dial in the dash the cable can break and allow you not to set warm.

Thanks. So far I can tell the mechanical knob in the center vent makes a change as the airflow sound varies when I move the knob from red dots to blue.


I had a Foxwell but lent it to a friend who lost it. I have an IR thermometer, so I'll give that a look. The footwell air is getting hot, so I don't think it's an air bubble.


The fun continues. And by fun I mean that this issue is bracketed by a frozen CCV that made the engine barf oil everywhere. Intake came off to fit a new Febi 'cold climate' CCV system along with rodding out the dipstick CCV drain.

Make sure you check the vacuum manifold for moisture and dry that out.

check your coolant level.

Low coolant = low heat

For some stupid reason the e53s don't have a low coolant warning light (at least mine don't).

The base model doesn't, "high cluster" models do. (or some trim level and above).

They all have the float switch. Would be very easy to add one.


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I don't remember "Black Bastard" giving a warning and it had the high cluster with a 3.0...but I could be wrong

I can't for the life of me understand why they would not have this feature on ANY model.

It's crazy! I had both mine and wife's e53 fail coolant reservoir and the first symptom is no heat. Wife's blew out the seam and overheated

Checked coolant level this morning but it was only down about 100mL.

Quite a few years back this truck blew the expansion tank so explosively it took the neck off the radiator too. But there was a good explanation after I figured it out:


Ex-wife was and is clueless about cars and had been driving it on hot summer days. She told me after it happened that the AC blew warm air whenever stopped in traffic but it got cold again once at road speed. The actual original defect was the clutch fan had failed, which then overtaxed and burned out the electric pusher fan in front of the condenser. Idling through a parking lot and BLAM!.


The easy solution was a complete rad/condenser/electric fan from a wrecker as well as a new fan clutch.


It probably was borderline overheating at every stoplight.

After a good long drive this evening I checked the hoses to the water valve and they were barely warm. Inlet a little warmer than outlets but not as warm as I would expect.


This thing has an auxiliary electric water pump. Maybe it's failed. I'll check that next.

Old enough m54 has aux water pump and whrn that fails you will have terrible cabin heat. It's below the intake filter.

Cheapo from Amazon incoming. ;)