Thinking of replacing Delanair unit

My heating and cooling system has worked pretty well over the last 10 years but now I have multiple issues. The transistors in the blowers have gone again so how speed only plus flaps are broken so I get AC even when heat is selected.
That’s OK for now but winter will roll around and I’m not looking forward to freezing my ass off. Have an entire spare system from my lower mileage spare car including blowers and all the bits plus the heater, evaporator.
Big job I suppose, any tips on removal etc gratefully received!

Larry …

Two years ago I removed the evaporator and both blower fan assemblies from my '89 XJ40. It’s not a job for the faint of heart. There are a LOT of things that need to be removed to get to them. That being said it’s all relatively straight forward and there’s no crawling under the car. The dash and center console have to come out, and a lot of things have to be moved out of the way. Not much in the engine bay other than the two evaporator connectors, two heater core hoses, and a few bolts holding the evaporator housing.

When you say “flaps are broken”, are you talking about the two rolling pin type blend flaps in the evaporator housing?

I believe that is the problem, probably the upper blend door. The centre vent flap appears to work fine although seal could be better. Plus both blowers are only working on high (again; 10 years since I changed the transistor etc)

Larry …

Removing both blower assemblies is a big job (as I’m sure you’re aware) but nothing like removing the evaporator. So if there is no leak in the evap you may not want to go there. If there is a leak in the heater core that can be pulled out without removing the evaporator housing.

You can check the operation of the two blend doors when you have everything opened up to remove the fans. one end of the blend flap has a motor and the other end senses the position with a potentiometer. If you remove the small motors on the right side you can manually rotate the two cylindrical flaps to see if they are working smoothly. I can’t see how they could “break” but they could be stuck or warped.I strongly recommend you do this to make sure it’s one or both of the blend flaps that’s the problem before you decide to pull the evap.

With all this being said if you do pull the evaporator housing you can now give the evap a serious cleaning and reline the inside of the housing around it. It was originally done with black foam and without a doubt it’s all broken down which allows hot ambient air to blow around the evap instead of through it… I replaced it with ridged styrofoam. This would be a huge step in returning you A/C to factory cooling.

Thanks for the tips Groove. I don’t have any leaks in the evap etc and my car gets down around 6 celsius, so 42f ish.
I think the upper blend door is stuck and of course the job of re and re-ing the blowers is complicated by the airbag on the passenger side. If I have to take the airbag out, it’s staying out -probably doesn’t work any more anyway.

This is good advice, appreciate it!

Larry …

I can’t recall if it makes a difference but be sure to mark the clock position of the blend flap spindle (the part that slides into the motor) before you manually rotate it so you can reset it where it originally was when you put the motor back on.

42deg F cooling is excellent !

All due to the aftermarket valves Joe and I fitted a few years ago :yum:

Larry …

What valves are you talking about ?

Heater hot water shutoff valves in the head. They failed with no replacement parts available for the 94 cars, so we replaced them creatively with aftermarket units.
It’s all in the archive.

Larry …

I believe there was originally only one vacuum operated water shut off valve on model years that even had one which could stop the water flow from the engine to the heater matrix, something like this …
Screen Shot 2021-07-19 at 7.20.20 PM

Interestingly enough I was just talking to an old friend of mine who has professionally been repairing British cars for about 200 years now. He said that even if the water valve is woking perfectly (which often they don’t) it only stops the flow of how water INTO the heater. He has often installed a second valve in the return hose to prevent hot water reaching the heater by way of conduction heating (heat transferring from one molecule to another). Both operate from the same vacuum source.

No, there were two types of valves. The second type was fitted to 94MY cars and because the production was very small in comparison to entire range, no spares exist AFAIK.

The late valve itself is very similar to the early type, but the input plumbing is quite different. Early valves (which are plentiful) cannot be fitted to 94MY cars.
Joe and I modified the input plumbing in similar but different ways allowing us to fit more efficient and inexpensive aftermarket shut-off valves.

here’s my mod:

If you have a spare hour or so to waste, here’s the whole thread from 2019

Larry …

Oh I was aware that there are two different valves used for the coolant shutoff to the heater matrix. Strangely enough because of your excellent posts on the very clever modification you made a couple of years ago.

What confused me was your reference to the after market valves (plural) that you fitted. My picture was meant to be generic (“something like this”) and actually show that only a single valve was used. Although I’m still intrigued with the idea of installing a second valve in the outlet hose.

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The plurality was me and Joe, not the valve! :smiley: