Rebuilding the heater for a combined unit with airconditioning

After deciding to add airconditioning with the centered original Frigiking F500 underdash unit I also need to rebuild the heater. So I had to cut the heater I finalised earlier into pieces.

kachel losgeslepen

Now I positioned the heating element slanted so I can create a combined aircon and heating unit.

PTC element schuin

And quickly added two sides which I would trim later.

zijkanten eraan

That heater part need to be connected to the airco casing containing a modern evaporator. To be able to squeeze in the smallest evaporator I could find I made a new cover and modified the bottom of the case.

bovenplaat airco

Airco evaporator fits nicely.

Airco met moderne verdamper

And under the dash the heater and airco joined up nicely as planned.

Airco en heater bij elkaar onder dash

Airflow blowers

Next question was how to position the blowers. I will keep one blower in the top to be able to vent fresh outside air. The other two can be added on the sides or one next to the connector of the PTC element and the other at the side.

indeling blowers kachel

To maximise the optimal use of the direction of the airflow the second option would be nice. So I explored whether that would fit.

blower naast HV connector

That triggered the question whether it wasn’t possible to position the heating element differently to get the connector out of the way allowing the blowers to be installed side by side.

blowers naast elkaar achter

But in practice that did not work out. The airco evaporator would be too vertical and the heating element too much in front of it.

PTC gedraaid

That brought me back to option 2. One blower at the back and one sideways next to the glovebox.

blower achteraanblower op zijkant handschoenenvakje

Added temporary supports to secure the heater and airco so I could work on it on the bench. Much more convenient that upside down under the dash.

blower achteraan op werkbank

Does become quite long and is using space that I also need for some enclosures for electronics. Luckily Ben Flierman from Tinustuning thinks along quite often for example to discuss the flow. He suggested to check whether the blower can be used sideways due to bearing design. Valid point! I could not find anything but does not seem to be designed to be used that way. I’m not taking chances.

Blowers orientation

On the bench, some new ideas emerged. In fact I reverted to my first option but with the blowers positioned horizontally.

blower1 zijkantblower2 zijkant

That could work out so I created a quick and dirty support.

provisorisch steuntje

To be able to test fit under the dash.

blower rechts blower links

Worked out very well.

Further developing the casing

I used my stud welder to attached bolts to allow me to have an adjustable connection between the heater and the airco case.

bout stiftlassen kachel

And while I was at it, I also added M4 studs for mounting the blower. Furthermore I modified the upper cover.

M4 bevestigingen blower

And closed of the sides of the cover and next to the airco evaporator.

zijkanten airco verdamper

I taped of the remaining holes so I could do a first flow test. Aren’t the blowers counter productive? Do I have sufficient airflow? Well, the result was stunning!

The above test was with all three blowers at full power. In that case is has almost as much airflow as our Volvo 940 on 4 or 5. Unfortunately it is quite noisy but that can be optimised in control software later on.

Now let’s finalise the casing and fully weld it.

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OldVolvo is a classic Volvo hobby blog by Lars Rengersen.

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