Failed heater blower motor vacuum actuator

I have been busy stripping my third Series III XJ6 parts car, a 1987 XJ6, of the remaining good parts before I have the carcass towed away. I have been disassembling the dash and after I removed the heater blower motors I discovered that both flaps on one of the blower motors were inoperative due to a failed vacuum actuator (RTC1914). I removed the failed actuator from the heater blower motor and cut it open with my dremel to find the reason that it failed. You will see in the attached pictures that the rubber diaphragm had failed and had a few slits in the rubber that leaked vacuum. I replaced the vacuum actuator with a spare used one that I had on hand from one of my other parts cars and returned the flaps on this heater blower motor to full operation again.
I am posting this so that others can see that this failure happens and that a failed diaphragm keeps the outer flap open at allowing outside air in the cabin at all times. This may not be a big thing in warmer climates, but in the middle of winter in some parts of the world cold outside air in the cabin at all times is not a good thing.
The only way to remove and replace the vacuum actuator is by removing the heater blower motor from the car, which is a complicated and time consuming thing to do.
Picture #1 shows the heater blower motor with the outer flap open and vacuum gauge at 0 showing the vacuum leak.
Picture #2 shows the vacuum actuator on my vise prior to disassembly. Picture #3 shows the vacuum actuator disassembled after I cut it open with my dremel. Picture #4 shows the slits in the rubber diaphragm that leaked vacuum. Picture #5 shows the same heater blower motor after I removed and replaced the vacuum actuator with the outer flap closed, the inner flap open, and vacuum being held when applied with my Mityvac.
If you are having problems with your climate control system flaps not operating properly it could be due to a similar failure. The vacuum actuator has a sealed metal cover over this diaphragm so the failure in the rubber is likely due to age. I suspect that there may be a bunch of failed climate control vacuum actuators (there are a bunch of them in each car) like this out there. Hopefully this post will help others.

BTW, one of the more enjoyable parts of my Jaguar hobby is learning how things work, discovering why things don’t work properly, and fixing things that are broken to return them to proper operation again. So this was a lot of fun for me. :wink:

Paul

2 Likes

Thanks Paul, I envy the part of your jaguar hobby of disassembling an entire car…so much to be learned doing so and I aspire to find the right parts car and do the same.

Sean,
Thanks.
Attached are two pictures of the last Series III XJ6 parts car that I parted out, a Claret 1986 XJ6 that I purchased for its nicely running engine to install in my former 1987 XJ6 Vanden Plas. I took these pictures as it was being loaded onto a tow truck to be towed away. As you can see there wasn’t much left of the car after I removed pretty much everything including every last nut, bolt washer, and screw. I find it fascinating to see how cars are put together. Over the past ten years I sold hundreds of parts from my three parts cars through eBay and directly to buyers. I shipped parts from these cars to buyers in dozens of countries and to almost every state in the USA. I have a map where I keep track of where all my parts were shipped to with push pins. This is another fun part of my Jaguar hobby. :wink:

The proceeds from selling these parts go towards buying the parts that I need for our five Jaguars. The circle of life. :slight_smile:

Paul

Thanks Paul, for letting us share this experience!

You never fail to amaze me with your perfectly clean and shiny parts - even an aircon unit pulled from a scavenged 86 car looks like a demonstrator from Delanair’s shelves!

But yes, I fully endorse what you said - and the satisfaction is even bigger if you’ve got the leisure time and do not depend on any particular item to work:-)

Keep that spirit … and us posted!

Jochen

75 XJ6L 4.2 auto

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I assume that such faults are not repairable, Paul - no way of putting the units back together after opening…?

Frank
xj6 85 Sov Europe (UK/NZ)
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Frank,
If someone was motivated enough, the RTC1914 vacuum actuator that I disassembled might be repaired. When assembled by Delanair, the two halves of the outer metal case were pressed together, with the rubber diaphragm squeezed in between, to create the seal. When I disassembled it I used my dremel to cut the edge where the two metal halves were pressed together to remove the failed diaphragm. If someone was motivated enough I suppose that the rubber diaphragm could be repaired (bicycle tube repair cement and patch?) or replaced (bicycle tube?) and the two metal covers sealed at the edge. I had a few spare good RTC1914 vacuum actuators on hand from my parts cars and I installed one of those and returned the heater blower motor assembly to working order again within an hour. I suspect that repair of one with a failed diaphragm would take a dedicated effort, much more time, and an element of risk over whether the repair would work over the long run.

One contributing factor is how difficult it is to remove and replace a heater blower motor. I am disassembling a parts car with no concern about putting the heater blower motor back into that car. If I had to do all of the work required to remove and replace a heater blower motor into an operational car due to a failed vacuum actuator I would want to be sure that the repair would work properly and last. There is always a risk that a used or even a New Old Stock vacuum actuator will fail the same way due to age, but given the choice I would probably go that route rather than try to repair one with a failed diaphragm.

Paul

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As long as the vacuum actuators are available, Paul - your description indeed confirms replacement a best option…:slight_smile:

Frank
sj6 85 Sov Europe (UK/NZ)
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And I assume all vacuum actuators are interchangeable…?

Frank
xj6 85 Sov Europe (UK/NZ)
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Frank,
The vacuum actuators on the left and right heater blower motors have the same part number RTC1914 and are interchangeable. There are however other vacuum actuators used in the Delanair MK II Climate Control System to control the Demister Vents, Center Flap, and more but they have different part numbers and are not interchangeable with the ones on the heater blower motors.

Paul