Thread: Heater Motor Resistor Mystery

I bought a shiny new heater motor that is supposed to be for my 1990 RRC only to find that it was a bit different

That new motor you bought has the resistor attached,
fairly sure your 1990 RRC should have the resistor
pack under the bulkhead (the section between the windscreen & bonnet)
If you remove the pollen vent on the passenger side you can see it in there.
The Heater/aircon unit is wired a bit different to earlier models.
That last photo, that plug is just to power the fan, and if you follow the loom back it will go to the resistors under the bulkhead.
Hope this makes sense

I've also pulled the bulkhead panel off and changed out that other resistor pack you mentioned as a preventative thing - bought an 'upgraded' unit from a supplier in the USA. My understanding was that it's for the aircon motors, not the heater motor and that the resistor for the heater motor is mounted inside the top of the heater unit.

So, do I understand you're saying that the resistor pack on the bulkhead is for all three (1 x heater; 2 x aircon) blower motors?

If that's the case, the resistor in the top of the heater is totally superfluous - is this correct? It's certainly not connected to anything...

Ahhh, the joys of make-it-up-as-you-go engineering!

cheers,

bidds

the resistor in the top of the heater is totally superfluous - is this correct?

On this model yes

bidds,

Afraid some of the above is perhaps misleading.

On a 90RRC the heater casing has a resistor pack located inside it - it's mounted on the nearside inside end of the housing.
There's a five pin connector on a multicore lead that goes through a grommet on the nearside of the housing. Inside the housing two leads (white/grey & black) connect to the heater motor; the other 3 go to the resistor pack.
The replacement unit you have is I suspect of a disco - it will be different coloured wiring but fundamentally the same. If using the motor mounted resistor pack it makes the resistor pack in the housing redundant (or you take it off the motor and mount it in the housing)

The aircon resistor pack is indeed mounted under the decker panel. It is a separate system in that it's blower motors have their own resistor pack but it's controlled by the same fan speed switch (and the aircon/recirc/fresh air switch) and the Heater/Aircon relay

Hey Hobbes,

Many thanks for your reply. Agree it's probably a disco bit but it's all I could find anywhere, all the online stores say it's for a RRC. They then sell you an adaptor lead - I could be bothered waiting and did as you suggest: rewired the new unit to resemble the old one exactly, mounting the resistor inside the heater unit.

The resistors are still basically not connected to anything as the plug doesn't now, nor ever had any wires mounted in the multiplug connector (third of my photos). I've not actually traced it yet (laid up sick atm) but roverv8 suggests that the multiplug attached to the wires from the heater blower and resistor pack will lead to the resistor pack under the decker panel. Makes sense, I checked the box my new resistor pack came in and it's called an 'A/C and heater blower resistor pack'.

I'm starting to think that the resistor inside the heater is actually for a RRC without A/C fitted; with slightly different wiring at the multiplug.

cheers,

bidds

Hey bidds!

I had to replace my heater blower a couple of years back and used a disco unit - so on the same page!

Ok, what you've done is correct - basically taken the resistor pack off the Disco motor, mounted it inside the heater casing. from this you've got five wires that terminate in the 5 pole connector. This issue being that the connector plugging into it has only 2....? and from your photo it appears to be a black and a white/grey...

This is really odd. There were a number of changes to the a/c & heater wiring between 89/90 model years - Is your chassis number definitely a SALLHAMM3GAxxxxxxx?

Even on the 93 model RRC, there is still a resistor inside the heater box, but not connected to anything.
There are 5 wires on the harness out of the heater box.
Red & Black, connected directly to the blower motor.
White, orange & green are connected to a resistor.
All 5 wires run down independently to a 5 pin plug, nothing spliced
Now the plug from the wiring loom has a 5 pin plug also but only has 2 wires,
1 is grey/white , the other is black.
Grey/white wire run back to a relay & then resistor under the bulkhead,
the black goes to ground
Ive physically pulled the loom apart.
At the plug grey/white connects to red blower wire,
Black to black


I also have an 87RRC wreck, also 5 wires running out of the heater box to the plug, the plug on that wiring loom has 4 wires, this model has no resistor under the bulkhead.

roverV8 - you are correct, my apologies.
The resistors in the the heater unit do nothing, narda, zip.

However, My 90RRC was a UK cop car (non-vogue model) and didn't have aircon fitted originally - This was done later by LandRover Oxford before I imported it, and it definitely doesn't have resistor pack under the decker panel!
Instead the resistor pack for that was fitted on the nearside inner wing, but it's a three wire affair and only does the a/c blower fans not the heater blower.

AFAIK, all Australian RRC from at least 1989 had a/c as standard fit so I guess they all have the combined resistor pack under the decker panel. Also there's a note in my manual that from 91 on, the air-con harness (and a few other things) were incorporated into the main harness so perhaps that's the point at which the heater box resistors become redundant on all versions...