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Discussion Starter #1
Hey guys! I just bought my first Lotus a little over a month ago. It's a 2005 Elise with 24,000 miles. Anyways, when I bought it, the seller told me that blower didn't work because it needed the resistor replaced. After doing some research, I found that this is a pretty common issue.

In the last month that I've owned the car, the blower has never worked. When I got in my car yesterday, I thought I could hear some air blowing, so I turned the fan knob up, and for some reason, the blower and AC is working fine now! I'm definitely not mad about it, I'm just wondering if anyone had an idea as to why it wouldn't work until now!
 

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The contacts tend to corrode. Perhaps a bump caused them to shift around enough to make a clean connection?
 

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The answer to why it works now is the answer to why it didn't work before - bad wiring. I'd enjoy it for now, but you still want to plan time to fix it for good. Note, I am not saying I know where the problem wiring is though. Yes, the resistor pack is a common failure point, but it is not the only one. It could be a loose fuse, bad connector near the trinary switch, crafty mouse, etc. There's just no way to tell without starting to tear into it and check things out.


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The answer to why it works now is the answer to why it didn't work before - bad wiring. I'd enjoy it for now, but you still want to plan time to fix it for good. Note, I am not saying I know where the problem wiring is though. Yes, the resistor pack is a common failure point, but it is not the only one. It could be a loose fuse, bad connector near the trinary switch, crafty mouse, etc. There's just no way to tell without starting to tear into it and check things out.


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Could not have said it better myself...

I was in the same boat. A/C and fan worked great when I bought the car. A year later, no A/C, no fan. 4 months ago, no A/C, but I had a fan. Present day, no A/C, no fan, about 300 hours of frustration, -$200 for a new switch (not installed yet), and very high hopes I may have fixed the problem.

If not, cyow5 and I will have a date night in the garage. haha
 

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Well here's an update. I got in the car this morning, and it didn't work again :/
I could feel a very gentle breeze coming from the vents, but it didn't change at all when I went through the fan speeds
 

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You can bypass the blower motor resistors and run the blower full blast in any switch position 1,2,3 in about 4 hours work. I can do it in two, now that I've done it once. I'm still working on ideas to get the other speeds using an electronic speed controller, but the switch output is positive and nearly 100% of the ESCs are designed to sink current using n-channel components.
 

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Electronic Speed Controller

You can bypass the blower motor resistors and run the blower full blast in any switch position 1,2,3 in about 4 hours work. I can do it in two, now that I've done it once. I'm still working on ideas to get the other speeds using an electronic speed controller, but the switch output is positive and nearly 100% of the ESCs are designed to sink current using n-channel components.

I bought this on a recommendation, I think from SirLotus, from another thread... https://amzn.com/B00H8GRFU2

Are you saying that won't work?
 

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I bought this on a recommendation, I think from SirLotus, from another thread... https://amzn.com/B00H8GRFU2

Are you saying that won't work?
It wouldn't work as a factory replacement, however, if you replace the 3 speed control switch with the potentiometer on that unit it should work fine and you'll have even better control over the fan speed. I would be tempted to run the orange and black wires from the fan back to the unit, not knowing how much resistance there is in the Lotus chassis, but that is probably unnecessary. The main thing is that I wouldn't want to cram my head under there again if the ground proved insufficient. With proper preparation, you can have the footwell work completely done in 20 minutes. An assistant is a nice to have.

I was trying to retain the factory 3 position switch by removing the potentiometer and using 3 different resistors from the factory switch. That won't work due to the internal design of the ESCs without adding three relays.
 

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Its coming from China so I haven't received it yet, but my intention was to use the included potentiometer, although I think it will need some machining to adapt the original knob, but we'll see.
I'm with you as far as the wiring. I'm going to error on the safe side and run a new 10 gauge power and ground straight from the blower under the dash where the new controller will be mounted and I'll extend the potentiometer into the housing. I'm hoping this will help me eke out just a bit more output from the blower as well. Also hoping not to have to have the front end apart again for a really long time.
 

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Its coming from China so I haven't received it yet, but my intention was to use the included potentiometer, although I think it will need some machining to adapt the original knob, but we'll see.
I'm with you as far as the wiring. I'm going to error on the safe side and run a new 10 gauge power and ground straight from the blower under the dash where the new controller will be mounted and I'll extend the potentiometer into the housing. I'm hoping this will help me eke out just a bit more output from the blower as well. Also hoping not to have to have the front end apart again for a really long time.
Are you removing the clam to do this or cramming your head into the footwell? If you're removing the clam, you might as well install replacement resistors in a better spot. If you're doing a bypass from the footwell, the wiring will be invisible if you run the orange and black wires straight up through the insulation space between the chassis and the blower and then grab the wires through the access panel with a harbor freight pickup tool, and then running them under and across to the other access panel and through the wiring harness rubber seal into the cabin. From there you could take them straight to the controls using a drill, or run to the passenger side sill/console and then across to the radio. Then, the tricky part is finding the hole that goes down to the HVAC controls, but it's there.

http://www.hotpursuit.net/Driving/Projects/05Elise/Blower.asp
 

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Yes, the clam is off and I am bypassing the resistors all together and running new 10 gauge power and ground from blower to the DC controller. I'll be bringing the wires in through the engine compartment pass-through and down under the dash where I will mount the DC controller
 

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Funny I was thinking about this today since I really cannot get the AC to turn down low enough.....

Truthfully there is no issue with fan resistors in general, just wet ones on the floor.
 

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If you move them off the floor though, there is a potential issue with airflow and cooling of the resistors. I just decided that the DC controller gives me better overall control without having to worry about the resistors burning out, catching fire or whatever because of airflow issues. If anything does happen, it's a one hour swap inside the cockpit instead ripping the damn thing apart again and losing a whole weekend.
 

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While these are not really issues, it is an interesting mod, so take pics document what you do and tell us how it works
 

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I understand your feedback, but this is my second time around with this resistor nonsense and I definitely don't want a third, so overkill is right where I want to be. Awaiting DC controller to arrive by weekend, will keep you posted.
 

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Oh, trust me, I doubled the size of the resistors and mounted them up above the heater. It is just my trust of Chinese electronics is lower than that of British engineering.....

My thought was to steal the idea of those who did the Tony Wa bypass and use a pot with a built in switch so you can always default to on high should the controller die when it is either 0F or 110F

Be careful your wires are not too rigid for the connections they are attached to. 10Ga is overkill[which is fine] but use a good service loop and ty wrap them to something pretty close so they don't fracture the terminals.
 

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Oh, trust me, I doubled the size of the resistors and mounted them up above the heater. It is just my trust of Chinese electronics is lower than that of British engineering.....
British Engineering? Don't get my wrong, I love this car and it is a marvel of structural engineering, but the resistors were fine, its the British engineering that made them fail.


Be careful your wires are not too rigid for the connections they are attached to. 10Ga is overkill[which is fine] but use a good service loop and ty wrap them to something pretty close so they don't fracture the terminals.
Agree with this, it was a concern. Here's what I did.....
 

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Nice work

Just glancing at the wiring diagram, it 'looks' like one could repurpose the low[yel] med[red] to be the pot leads and keep the high[orange] to be switched on high if ever needed. It may also preserve the functionality of the switch turning on the ac and activating the fresh air vent and blend door. The controller may not appreciate 12 volts on its output, but since DC motors tend to self generate I kind of think it isn't an issue
 

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My car is currently at dealership and I've been told my resistors are going bad. Sadly they say the front clam has to come off to fix this, so I passed on getting it done due to labor costs. Can this mod actually be done without removing the clam? I'm planning on living in Miami and reeealy want my A/C working, but geeeze not if it costs labor for clam removal...

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pretty much yes

I do not like the lotus setup for the resistors, so I would not recommend it. I think it further blocks the airflow to the fan

removing the clam is not difficult, but it is a bit time consuming
 
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