More powerful cabin fans


Has anyone had good results installing more powerful cabin fans in a XJ6 series 1?
The low speed is very weak air flow, but the high speed is super noisy.


‘More powerful fans’ means more noise, Brit…:slight_smile:

Nominally, altering fan blades/funnel may reduce the noise, but the fan speed is also regulated by resistors. You may access the resistor pack and alter fan speeds to your liking by changing the resistors…?

xj6 85 Sov Europe (UK/NZ)

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There is a bit of contradiction there…
You want more power, but this will make more noise.
But you don’t want the noise when you already have the power…

The flow in low speed might seem weak but keep in mind that you have two side vents, two foot vents, a big vent plus some leakage to the windshield vents.
That’s a lot of vents.

Maybe the SI is different in that aspect from my SIII, but my system is pretty adequate on retaining the cabin temperature with the fan in low speed.
Actually, I have a switch that disables the fans, and most of the time my fans are off. As long as the car is moving it’s enough.

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There are defrosters, side vents and foot vents in the S1, plus one to the rear and rear footwells. There is no center vent.

The E types use a fan unit and motor from a different car for more air flow.
If your low speed is too low for you you can try bridging a coil in the resistor, but no guarantee that works well. I’m happy with mine so far.
Mine have not been loud at full speed but I only tested them on a 14.4v drill battery (with vacuum so it actually blows air, and it will not really deliver 13v under load). That battery is powerful enough for windows and all lights, so maybe you have a ducting problem or bearing failure?

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Thanks for the help on this. I guess I’m trying to find a middle ground between the low and high fan speed switch on the dash. The 2 dash vents and rear facing work. The plumbing for upper dash and footwell is not functioning.
I’ll look into the resistors.
There’s no cold speed variation knob. It was missing when I purchased. And when I had the 134 ac fitted, my guy put an ac on / off switch. So that might be my issue too. I’ll add a photo later today.
I also have a 75 XJ6C , and the lower fan speed is great.

I have GM fans in my 1971 XJ. They put out about 30-40% more air but on high speed they are noisier.
They demand a gasket of silicone about 1/4 inch thick to space the outer ring out so the metal blades

My only problem is the evaporator freezing up. I am getting

an appointment to replace the drier and evacuate and recharge hoping there is moisture.

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Thanks for the info. Ill look into the resistors and the GM fans.

Did you swap the Jaguar squirrel cage onto the GM motor, or did you go with the GM squirrel cage? It looks to be the wrong shape.

I’m not so sure changing motors or squirrel cages will solve your noise problems. I believe the noise is from the movement of air through the system, not the fans themselves, unless the noise your are getting is mechanical, such as the cages rubbing on the inside of the housing or bad motor bearings. Upping the speed of the fan is only going to make the noise worse as more air is pulled into the fans and pushed through the heater box and vents. Before you make any changes, make sure the system is working properly with no obstructions or leaks. It was never a very good system to begin with.

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when the XJ hit the market in 1968 it was way ahead of its time in many respects - but not with respect to heating and ventilation which became the only significant technical progress for SII cars in 1973.

And yet, even SII heating and ventilation is marginal, compared to modern cars. Three fan positions seem to only give more noise, not more air. More powerful fan motors or “bigger” fans won’t work - you’d have to design an entirely new environment with larger air ducts, smoother surfaces, more efficient fans creating less air turbulences to end up with something really satisfactory.

For the moment try to purge air from the heating circuit to be warm in winter and make use of the front triangle windows combined with the “Air pull” direct connections to the front eyebrows to have moving air in summer. Maybe check whether these are still connected to the fresh air inlets in the front footwells.

If you have an climate system installed the SII seems to be a considerable improvement over the SI system. Fitting a SII (or for this purpose SIII ) system is not easy though as the entire center of the car was redesigned in SII.

Good luck


XJ6L 4.2 auto (UK spec)

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IIRC in the Series 1 (at least) the fans spin in opposite directions - may be wrong. Might be worth checking that each is in the correct spot or see if they have different part numbers. Paul.

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If you only want to increase the medium speed a bit: mine is above the RH fan and shortening the length of the coil could by trial and error give you a nice intermediate speed. I‘d bridge it with a screwdriver first and then jam something in (I can imagine solder melts - not sure but who wants to find out?) if it works out.

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IIRC, if you run a centrifugal fan backwards you still get airflow but considerably reduced. In commercial installations, we used to check for the correct rotation of a 3-phase blower fan by turning on the heat and measuring the temp at the output grille. If it was really hot, like 120 degrees F, we knew the blower was running backwards; fixed amount of heat with a reduced amount of air = high temp. Swap any two wires to the motor and try again.

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Depends on whether it’s directional like ours are, or bidirectional. If the fins are straight radii as in some power tools it is reversible, but I can almost assure you this one does nothing in reverse. If in the wrong case it will at least be ineffective.

The fans had different part numbers (BD32019/BD32020), then the same, probably with the introduction of AC? It’s not very clear to me from the parts book.

Looks like they spin in opposite directions.

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No, it also depends on the housing. Gotta work with the scroll, not against it.

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I meant that when I said that they will be at least ineffective in the wrong case. So a cage fan whether directional or not won’t do well if it spins the wrong way for the blower case.

I have fitted GM fan, with 420G squirrel cage (almost identical to S1 XJ6)

They have the capability to move a great deal more air, and 4 speeds with the factory resistor pack

I have not done this yet, but using PWM (pulse with modulation) as a speed control would allow infinitely variable fan speed

In summary, the fans move more air, and are noisier, but the “CFM per decibel” is somewhat improved. I do not think they are noisier than the Jag fans on low setting, but do move more air

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I guess we’re saying the same thing. Understand three phase, used to be power systems electrical engineer. Paul.

Apart from the air speed/noise, Brit - how does the system otherwise work? Fan speed is only one factor in cabin heating/cooling - an efficient system needs less fan speed…:slight_smile:

xj6 85 Sov Europe (UK/NZ)

Y’know that squirrel cage we looked at in the photos above? If you make the squirrel cage larger diameter, it can be narrower and turn slower to develop the same airflow. That makes it quieter and more efficient. Unfortunately, it also takes up more space, especially when you include the scroll case surrounding it.