DIY Blower Motor Resistor Pack Replacement

[rob13572468]

Over the winter I finally had my resistor pack go bad and decided to replace the resistor pack as i had the front clam off for repairs anyway. As it turns out the $150 dollar resistor pack replacement part is actually about $12 in actual parts. What follows is how to do this if you want to DIY. The whole process took a couple nights to do and was almost entirely the disassembly of everything required to get the blower motor out of the vehicle to fix the pack. The resistor pack is on the bottom side of the blower motor so you have to remove it to get at the packand to do that you need to remove the HVAC airbox first. I wont get into the disassembly of the HVAC parts because its pretty straightforward and has been covered here before. Ill start with the actual repair...

[rob13572468]

This is the replacement resistor pack and the other pic are the individual resistors. The part is literally just the resistors mounted to a plate but otherwise its the exact same. The resistor values are 0.05, 0.22, and 0.27 ohms at 50 watts and the parts are available thru mouser (Mouser Electronics - Electronic Component Distributor)

284-HS50-0.05
284-HS50-0.22
284-HS50-0.27

They currently list at $4.70 each so thats $14.10 US for all three.

[rob13572468]

This is the old resistor pack.. As you can see its completely corroded and was obviously mounted in the most ass-backwards fashion. What I believe happened is that lotus sourced the unit for RHD configuration and the resistor pack was to be on top but when they built the elise they moved it to the other side of the vehicle which put it on the bottom.. Dumb.

[rob13572468]

The corrosion problem is not just one of standing water. As the pics show, even the wiring to the blower had become corroded all the way through and needed to be completely replaced. Oherwise the wiring itself starts to heat up due to internal resistance and the blower runs more slowly. I used 10 gauge primary wire for both power and ground.

[rob13572468]

The completed wiring was run to the top part of the front of the vehicle. The new resistors were not mounted in the original position as there is no good reason to leave them there. The resistors were instead mounted next to the fuse panel for easy access.

[rob13572468]

This is the harness with the new wires from the blower motor run directly into the connector. You can disassemble the existing connector and cut the old wiring off of the connector pins and then solder new wires to them. The connector can then be reassembled. This shows the wiring ready for everything but with the resistors not attached. Also note that the fan can run without any resistors if you only care about full speed. (full speed mode connects the orange wire to the blower directly without any resistor)

[rob13572468]

Below is the wiring diagram for connecting the resistors. I choose to mount the resistors to a small aluminum panel and bolt it next to the fuse block. The wires are simply soldered to the resistor ends. Once everything was completed I actually got much higher airflow from the blower motor because of the larger primary wiring and good connections.

[TheViper]

Great report, thanks Rob, much better to locate it where it's at least accessible for when it next goes. If I had to do it I would dispense with the resistors and just directly wire, as I only use #3 position.
Cheers,
Michael

[rob13572468]

Originally Posted by TheViper

Great report, thanks Rob, much better to locate it where it's at least accessible for when it next goes. If I had to do it I would dispense with the resistors and just directly wire, as I only use #3 position.
Cheers,
Michael

no prob... The actual reason that the resistors are there at all is because the blower itself is used to cool the resistors. When you remove the resistor pack there is an opening leftover wher ethe air would cool the casing. That needs to be covered when you move the resistors but i lost the pic that i took. (it was just a piece of ABS plastic cut to size and siliconed in place.)

The resistors are really not necessary: i had it wired just as you mentioned for a couple of months until i got around to putting in the resistors. Honestly the middle setting is totally redundant IMO... you could use just one resistor at about 0.5 ohms for both the 1 and 2 settings and that would give you a slow position aside from the fast one.

[TheViper]

I wondered why Lotus placed them in such an inaccessible location, but the cooling thing makes sense. Being in Florida, in the winter I never use the Fan being that the top is off, and in the summer with the hardtop on I only use #3 position which is direct without the resistor. Thanks again for a great informative post.
Cheers,
Michael