Heater motor blower resistor needed for 1977 xj6

Would there be one for other years that would fit my series 2 1977? Lawrence

Try to contact David, at David XJ.com
He has all kinds of parts for those cars.


Welcome on board, Lawrence…

It really is a really a resistor pack- with two
resistors on earlier cars, and 3 on the S3. As the resistors just varies fan speeds, you can use a resistor pack from any series car. Relays connects power to fans through the relevant resistor - you may have to experiment with a non-standard pack to get the desired fan speeds…

But what is the actual problem - have you identified a burnt resistor?

xj6 85 Sov Europe (UK/NZ)

I add my welcome greetings.

Can’t tell where you are on our planet.

And electronics are not my strong suite!!
So, this may or may not help.

The resistors might be generic. And as such color coded as to values. And a means of locating them (?). End for end that is. Might be confusing that with a diode!!!

A local electronics store might have what you need. a solder job to install. Radio Shack in a nearby town around here has 'em. along with the usual electronic toys!!

My Jeep uses a series of them in a rack. Not working at the time. so, it’s AC fan is either on full speed ort off. Not an issue as when we need AC around here, full speed is it!!


Frank, I haven’t identified the resistor as the problem; at this point just a strong guess because there appear no other “no heat” causes, e.g., leaking core, etc. One friend suggests that some vent door may be the issue. At this point, the fan works, and
the anti-freeze is not leaking anywhere, and with the side vents closed there is tepid warm air but no real heat.

Thanks for your suggestions. PS, this car is in upper New Hampshire, USA.


get a test light on it

corroded connectors often afflict heater resistors


I’m not clear on your problem…

Fan resister pack is made up of several lengths of NiChrome wire…they seldom fail.

However, in your last response you suggest a “no heat” scenario.

Understand if the environmental temperature is close to 85F…the system will never go into heating mode as the system temperature inputs would tell the amplifier that the system has reached a balanced status.

Also be aware that the engine coolant must be to 105F for the blowers to be turned on…this design feature was created to prevent occupants from having cold air blown on them in the middle of winter.

Lastly, (at least on series 3 cars) high fan speed is disabled in heating mode.

If you can offer a bit more information on your testing procedure and what is failing…we may be able to offer more advice.

You may or may not actually have a problem.



The fan resistors is purely relevant for running the fans, Lawrence…

If the fans are running at the different speeds as set by the fan control; the resistors are working as they should.

Gary raises two relevant points; the resistor pack is very reliable - and there is a difference in fan control between earlier cars and the S3 set-up. Do you have AC…?

With lack of heat the difference between the ‘old’ and S3 requires some difference in fault-finding. However, some commonality; it is pertinent to check the air flow temp with a thermometer - to supervise changes. Then to verify that air speed through the vents is relevant to fan speed - really fast with high fan speeds set. Also check that the defrost vents are closed unless ‘def’ is selected…

Both system are vacuum dependent and vacuum supply should be checked. Locate the vacuum canister, a flat round tin, located at the inside of the engine compartment near the brake servo. Briefly run the engine and stop, then disconnect the vacuum hose - there should be a hiss as air refills the canister.

On the ‘old’ system; vacuum opens the heater valve - and lack of vacuum will leave the heater core cold - check for vacuum on the heater valve hose with the engine running. As a back-up, with the engine hot; check temp at the heater hoses - if there is no temp difference; there is no circulation through the heater core. Heater core blocked or heater valve not open - disconnect and reconnect heater valve hose 9with vacuum present) to check if the valve is moving…

Just to begin the remedial process…:slight_smile:

xj6 85 Sov Europe (UK/NZ)

Gary, all of your remarks are pertinent; I need to use them to diagnose the problem more accurately. Thanks so much. I will let you know what happens. Lawrence