RH fan turns wrong way round - from factory? (SOLVED)

[jagwit]

Having removed the radiator of my “new” OTS to have it serviced, I was also repainting the cowling and installing new rubber flaps. Upon refitting the original fans, I tested them by applying 12V to both Brown and Green wires and then shorting out the connectors to the fan switch. Both fans ran…

But when they stopped, I noticed that the RH fan was turning the wrong direction, pushing air into the cowling instead of pulling it out!!! Thinking that perhaps the fan motor was at fault, I temporarily connected two other original fans (that came out my FHC when I fitted VW fans to that car) and both of them also turned in the wrong direction!

Suspecting that someone had fiddled with the wiring, I then checked the harness carefully but could not find any evidence that the original fan harness had been tampered with anywhere! The Black/Green wire was feeding the earth wire of the fan motor and the Black earth wire was feeding the green 12V wire of the fan motor.

My conclusion is that the harness male/female barrel connector on the RH side had been installed the wrong way round with Black/Green going to the earth wire of the motor (Black in the case of motors on my car) and the Black wire going to the Green wire of the motor.

Seeing no elegant way of correcting this, I cut both black/green and black wires of the harness, crimped connectors on all 4 ends and swopped them over so that the fan now also sucks air from the cowling. Now she runs just below the N on highway cruising, between N and O in town (74degC thermostats).

This car must have had this situation for all of its 48 years!!! Is this common??

[Gravygraham]

You’ve probably already discounted it but might the offending fan have been fitted on it’s spindle the wrong way round?

[jagwit]

The fan can not be mounted the wrong way round, and even if it could, would still be going wrong way.

[lowact]

Sounds uniquely weird. My greens line up. The interface ( N to NB) is stepped, moulded plug? Hard to accidently build one of these backwards, unless feeling bored and mischievous ...
Solenoid and downstream wiring al original?

[jagwit]

Solenoid and downstream wiring al original?

I could find no evidence of any tampering on the cowling wiring.

But now she runs sweet just below N of Normal. I have a video: https://youtu.be/omgm1H2guCQ

[abowie]

You'd hardly expect something built by BMC in the UK in the 1970's to have been assembled by people who in any way cared. I suspect it was just badly done, from the factory.

[ReconPilot]

If I were a betting man I'd say a PO has tinkered with the fans, probably replacing the carbon brushes. Try this for a fix.
1. Remove the fan that's running in the wrong direction.
2. Make an alignment mark to the body/cap.
3. Remove the two long screws that hold the body to the end cap.
4. Rotate the body housing 180 degrees.
5. Reinstall the two long screws.
6. Test the fan to see if the blade is now turning in the correct direction.

The first S3 (1971) I owned I rebuilt the fans. When installed one turned backwards. I made the aforementioned change and that fixed the problem. A close examination of the case/end cap will reveal a small line mark made by Lucas. That line is for correct orientation of the body/cap relationship.

Stay Safe and Happy Trails,

Dick

[jagwit]

A close examination of the case/end cap will reveal a small line mark made by Lucas. That line is for correct orientation of the body/cap relationship.

Good info Dick!!! I'll go check.

[jagwit]

A close examination of the case/end cap will reveal a small line mark made by Lucas. That line is for correct orientation of the body/cap relationship.

Spot on Dick!!! Aligning the two marks result in the fan turning the correct.

tn2_20210406_135148.jpg (73.49 KiB) Viewed 3082 times

[ReconPilot]

Great.... Kinda thought that was the problem. The fans are basic, pretty bullet-proof but alignment on re-assembly can be overlooked. No mention of the alignment marks in any of the Jaguar literature either!!!
Made that error years ago. Noted. Passed along and now happy to have been some assistance.

Stay Safe and Happy Trails,

Dick

[christopher storey]

This is extremely useful information, and perhaps Heuer will make it part of the database ?

[Heuer]