XJS Air Conditioning

(Evan) #1

I have a1984 XJSC 3.6 RHD. Manual says the Air conditioning motor to have a 10A fuse. The fuse box cover states 50A.
Handbook states RHD is 10A and LHD is 50A.
Would be grateful if someone could tell me which to follow and why the difference.

(Gary Crosby 75 XJ6L, 85 XJ-S, 09 XF Supercharged.) #2


There are 5 fuses in the AC system.

First please understand there is a difference between British slow blow fuses and American fast acting. The car labels are listed for slow blow British fuses. Generally speaking…fast acting is approximately 1/2 the slow acting rating. I don’t have the file in front of me…but do a quick Google search for accurate values.


1- 10 amp should feed the power to sensing circuit including the amplifier and servo. (LH fuse box)
2- 1 amp fuse in ground leg of AC amplifier. (LH trans tunnel ground point on heater box)
3- 50 amp feeding power to the fan blowers (RH fuse box)
4- power to AC compressor in line holder just ahead of ranco thermostat. (RH trans tunnel…up high on side of heater box)
5- AC compressor thermal fuse located at compressor. (At AC compressor- engine bay)

Hope that helps


(Evan) #3

Thank you for the prompt input. Had no idea the difference - have looked up the comparatives.
I would assume that all Amp ratings quoted in the hand book /fuse box cover would be British standard - so for blowers RHD it is 10A and LHD it is 50A.
Why the difference between the two when all other fuse specs are the same?
Was it perhaps that LHD had two blowers operating and RHD only one?
Many thanks

(Gary Crosby 75 XJ6L, 85 XJ-S, 09 XF Supercharged.) #4


I think there may be some confusion…the 10 amp fuse powers the sensing circuit, minus blowers. The 50 amp provides power to only the blowers beyond the fan relay pack.

There are two fuse boxes…one under the left dash and one under the right dash. Blower fuse is is one fuse box and sensing circuit Fuse in the other…

Fuse values listed are British value “slow acting” fuses…if you are in the US and purchasing fast acting fuses…installing a 50 FA would be way to high and could cause problems.



(Kirbert - author of the Book, former owner of an '83 XJ-S H.E.) #5

I dunno if the Brit fuses are significantly slower, but that’s not the difference in rating. The Brits rate fuses at the current at which they will blow. The Americans rate fuses at the current at which they don’t blow – the current the circuit is expected to carry continuously. The difference appears to be roughly 2:1.

(Evan) #6

Many thanks – yes I have had it confirmed by my garage that it must be a 50A British and that the spec on the cover is the definitive one.
Thanks again

(Kirbert - author of the Book, former owner of an '83 XJ-S H.E.) #7

A 30A American fuse would probably be a suitable replacement.

(Evan) #8

Hi Gary

50A inserted – all working sensationally.

Thank you for the help

Best regards