So i just got my hands on an 87 XJ6 from southern Cal, got her over to Brooklyn in the middle of this winter we're having after a week or so the heater has started to work intermittantly. The thing will cut in and out at will, no reason or rhyme. Any advice on what the issue is?

 

Can you be a bit more specific on the fault symptom. Does the fan turn itself on and off, or the heat just come and go ?

Is your car an XJ6 Series 3, or the later XJ starting in the UK in 1986 called the "XJ40" by this forum to distinguish the model from the Series 3.

 

If a USA S3 version, I'd start with the vacuum supply to the heater valve on the fire wall.

Carl

 

the XJ-40, (unoficially the "Series 4"), did not arrive in the USA until the 1988 model year, so it must be a Series 3 XJ-6 which was sold until 1987 in the USA, (and sold in Canada until 1992 as the 'V12', the 12-cylinder engine in the Series 3 body).

if it's a Series 3 with the 6-cylinder engine, he's lucky, easier to fix.

 

It is the fan that works intermitant. When I turn it on it runs for a few seconds then cuts out again. It is an American series 3 car.

 

there are two fans/blowers, one on passenger side, one on driver's side. Both are controlled by a large Relay mounted on the driver's side, behind the vent panel nearest your right Knee;

remove two phillips screws at the black plastic vent which directs air to the floor, then pull the upholstered panel towards the engine side to remove it.

look for the the large Relay box that has many wires connected to it; With engine running, transmission in PARK, Heater Fan knob in AUTO, Heater TEMP knob at 85, wiggle each wire to see if you can get a reaction, (a "reaction" as in the fans going ON or OFF if you wiggle a certain connector).

 

Thank you so much Jose. I'm going to take a look as soon as I'm off work.