Blower motor dont work Max speed

With an outside temperature of 80 degrees, I turn on the air conditioner and the fan starts at max speed and then goes down to minimum speed. I set the selector to max and continue to minimum. A few days ago I changed the voltage regulator and it seemed that it had been composed, but soon I continued with the problem. Has the same thing happened to someone? What would be the problem to solve?
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Is this a Delanair MkII or MkIII?

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What voltage regulator are we talking about? On the alternator?

What year is your XJ-S/XJS? Jaguar produced them from 1975 to 1996 and made lots of changes along the way. Please let us know which model year your car is.

Paul

Yes the alternator.
Os charging 13.8

Muy jaguar is xj s he oct 1982

That’s a Delanair MkII.

Your fan speeds are controlled by a pack of four relays, all built into one box. IIRC, it’s near your right knee in a LHD car. It’s probable that one or more of those relays is misbehaving. You can replace one or all four of those relays with generic automotive relays.

There’s also a resistor pack, but a failure there is not intermittent; when it quits working, it never works again. Just as well, it’s a lot harder to get to!

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Your car has two blowers. Are we to understand they are both misbehaving together? Or is it possible that one is quitting altogether while the other is running properly?

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Yes alternator regulator

Rodrigo,
Your 1982 XJ-S has the Delanair MK II climate control system. Do you have the Drivers Handbook for your car? The Delanair MK II has some well known failure modes and its automatic operation is not intuitive.

What happens to the heater blower speeds if you turn the mode selector switch to windshield demist position? Do the blower motors both blow on high speed? Do both blower motors work? You run one of them at a time by removing the appropriate fuses in the under dash fuse boxes to isolate their operation.

The A/C amplifier in the Delanair MK II system is a high failure item and when it fails the system operation is very unpredictable. If you search the Jag-Lovers archives for “A/C amplifier” you will find lots of posts about the problems people experienced and what they did about it. The Delanair MK II system was also used in the Jaguar XJ6s.

Paul

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Sounds good. Not the problem here. I’m still betting on those relays.

True. However, there is a connector behind the knee bolster in the starboard footwell that has a dozen wires but two of them are a distinctly different color scheme than the rest. Those two connect to the servo motor. If you unplug the connector and connect a 9V battery to those two wires, you can manually drive the servo back and forth. One direction is toward more heat and the other is toward more cool – although it’s quite an operation, there are lots of cams and links moving back and forth. Whatever, using this method you can completely bypass tthe control amp and operate the system manually. That’s great for diagnosis, you can see if it works fine without the amp (meaning the amp is likely the problem) or if you still have the same problems.

I’m still betting on the fan control relays.

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Kirby,
It will be interesting to see if both of his blower motors work and if they both go to high speed when windshield demist mode is selected. My money is on a bad A/C amplifier having experienced a few of them in my Series III XJ6s.

Paul

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