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Thread: HVAC Fan Resistor Pack Bypass is Successful! Reply to Thread
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  Topic Review (Newest First)
10-10-2018 07:52 AM
exigegus It's still gross

Hey its you car, do what you want.

https://www.lotustalk.com/forums/f31...al-diy-400993/

The additional things you can do when the clam is off are worthwhile
10-10-2018 07:25 AM
BrianM Don't want to pull the clam. And I'm very good at cutting and adding patch panels.
10-06-2018 03:54 AM
exigegus Seriously, don't do this, it's gross.

Try the hemostat and remote camera method, far less hackery
10-05-2018 10:54 PM
Roundabout
Quote:
Originally Posted by BrianM View Post
Ah man the pics are dead on this thread. Anyone have a diagram on where to cut? I can figure out the rest.
My Notes:
2005 Lotus Elise, 1.8L - HVAC Blower Resistors

LT:
https://www.lotustalk.com/forums/f31...essful-116134/
10-05-2018 08:07 PM
BrianM Ah man the pics are dead on this thread. Anyone have a diagram on where to cut? I can figure out the rest.
12-01-2017 09:14 AM
exigegus https://www.lotustalk.com/forums/f3/f...al-diy-400993/

https://www.lotustalk.com/forums/f92/...-wa-how-26740/

https://www.lotustalk.com/forums/f313...rework-348738/
12-01-2017 09:07 AM
exigegus Well, I for one, would not cut a big gaping hole in someone elses car. This is the worst option of all.

There is a thread where a guy used a little camera and hemostats or somesuch to get in there

Removing the clam is not a huge deal, draining the coolant and AC systems are more of the pain
12-01-2017 08:48 AM
oddcarnut Being lucky to have been given a multi-year loan of a 2005 Elise while the owner is working overseas, I'd like to tackle fixing the blower fan issue in his car. I see lots of options on the forum. Is there a summary write-up some place for the VSC option and pulling wires without the clam removal? Any suggestions on a VSC to use?

Thanks,

Ken
02-26-2017 03:56 AM
dward69 Make your life easier, pull the orange/red wire connector off the motor cut the wire as close to the foam as you can. Solder new wire on and shrink tubing. Then use very long hemastat from harbor freight. One try and it was on. Easy
02-26-2017 03:49 AM
dward69 I used a air saw from harbor freight, much neater and fast
06-16-2015 11:03 AM
Roundabout Normally, I wouldn't consider cutting a hole there, but since this car has an amplifier cutting off the passenger side inlet, and since Lotus put a big hole there anyway, it just seemed like the best thing to do. The vents flow more air now and it's an opportunity to put a nice plate down there. I had no problem cutting a very clean hole with the air die grinder and a cutting wheel. The whole job can be done in 2-3 hours.

I have a design that uses a plastic weave filter that would slide up out of the car for cleaning. I will probably implement that on my other car when the connections corrode.
06-16-2015 08:36 AM
Doge I still can't believe people cut that big hole there! Taking the clam off really isn't that difficult! Yes, getting the air box in and out of the car was kind of a pain, but, I'd rather do that then cut the hole. Lotus should have put a removable panel behind the panels, although they probably didn't realize every car would have a resistor problem.
06-15-2015 04:38 PM
Motard Screw it.

If mine gives out I will just take the clam off... I am certain I will find other things to do in there. I have experienced enough Lotus Karma on my ride that I will take the fight to the car when it acts up. I could also do all the other AC mods SirLotus has provided us.

I was very pleased when I took his advice and took the recirc panels off... I hardly use AC, but well I love increasing efficiencies... OCD

Great write up !
06-15-2015 02:16 PM
Roundabout
Quote:
Originally Posted by Roundabout View Post
@SirLotus
I remember seeing a mention about a motor speed controller, but I haven't been able to find the link again. It looks like the motor could draw 12 amps/144 watts. I need to find a controller capable of that and then presumably use some small 1/4 watt resistors to replace the potentiometer that typically comes with the controller to get 3 speeds using the factory switch.
I found a high wattage 12V DC Variable Speed Motor Controller online for $20. The VSC uses MOSFETs in parallel for current and a 555 Timer for pulse modulation. Unfortunately, it modulates the chassis ground side of the fan as the VSC circuit power and blower power are connected together on the VSC board.

So I went inverted under the pedals to cut the black wire and then extended both black wires into the void under the passenger sill using the same routing as the 12v+ blower wire. This gives me the Power+/Blower+, Blower-, and Chassis Ground connections on the VSC. Now the VSC controls the fan, but the Lotus knob doesn't fit the VSC's potentiometer shaft. That is probably fixable without too much trouble. Unfortunately, the VSC board is about a half inch too long to sit behind the Lotus HVAC control panel. While it would be technically superior to have the infinitely variable fan speed, the Lotus switch would no longer click the same as it does now. Call me crazy, I like the click.

So I desoldered the potentiometer from the VSC board. The idea was to select 2 sets of resistors in a voltage divider configuration in order to provide fixed Low and Medium speeds through the VSC and use the original Lotus switch as intended by Lotus.

Unfortunately the Lotus switch combines the power on function with the fan select function. The VSC has separate power on and fan speed functions. The Lotus switch has 5 pins that takes one 12v+ input from the ignition and outputs 12v+ on two of the remaining 4 pins on any given fan setting: 1, 2, or 3. The pin next to the 12v+ input is always 12v+ on any fan setting except off. This terminal supplies power to the AC switch on the Lotus so that the AC can only be activated when the blower is turned on. This is somewhat different from most cars since one would normally turn the AC on and get blower at the same time. Whatever, we adapt.

The problem then comes that the Lotus switch produces 12v+ that would likely be at a different potential from the VSC potentiometer input, so I wouldn't want to interconnect the two. So I'd need to use a relay to activate the VSC board and then a relay for each of the Low and Medium speeds.

At this point, I decided to quit and leave the switch in place and have high speed blower whenever the switch is on any speed.

But I thought I'd post this up in case someone has any other ideas.
05-25-2015 12:47 PM
Roundabout Now that I've done this, I really think it was the way to go. I disconnected the AC on my other cars to do heater cores and it was always a pain and there's no guarantee that the AC will be charged correctly, proper PAG refill, etc. It's better to just not mess with it. A note for those that change their Accumulator/dryers. You must measure the qty of oil that comes out of the old dryer and then use that as a guide on PAG oil to re-install.

Tools Required:
An assistant (need not be mechanically inclined)
Wire cutters - smaller is better
1/4" die grinder with cutting wheel arbor and cutting wheels
Flash light
Wire stripper
Wire Crimper
Flat file
Duck tape
9-12 feet of 12 AWG Marine Grade wire
12 AWG butt splice connector
Heat shrink tubing
Lighter
Vacuum cleaner with hose
Claw style pickup tool
Non-petroleum-based lubricant

I found an assistant to simply hand me tools. I used an air-powered die grinder with a high speed cutting disc, which I have lots of experience using, and cut the perforations out very nicely in less then 7 minutes. Filed off the sharp edges with a flat file, covered with duck tape and started in on the orange wire. Based on other people's experience, I intentionally tried to pull the resistor end of the orange wire to see if I could disconnect the wire that way, instead of cutting it. With little effort, the burnt and oxidized connector came out of the resistor pack. That allowed me to have a bit extra wire to handle. I cut and stripped the wire and noticed that the oxidation was inside the insulation. I then took a saturated solution of white vinegar and salt and cleaned the corrosion off of the wire end. This took the longest, because there was no way that I wanted to get any of that on the Lotus, so my assistant handed me a single Q-tip at a time. After cleaning the end thoroughly to remove the acid, I butt spliced on my marine grade (fully tinned) 12 AWG wire. Following Sir Lotus's instructions, I went straight up to 12 o'clock, through the foam insulation, and the wire ends up below the brake booster. I pulled the wire up with the claw pickup tool and pulled it up. I slipped on 2 feet of convoluted tubing and then snaked the wire towards the passenger compartment using the claw pickup tool. I went under the booster, and under the intake hoses, so the wire/tubing ended up being completely invisible. I then lubed the wire with KY and slipped it into the main wire harness rubber plug. The lube was necessary because the rubber plug seems to have some sticky substance on it that impedes sliding a wire through. At that point, the wire will be visible under the passenger side dash. From there, you can go up into the passenger side storage compartment, under the airbag, to the radio compartment and then down to the HVAC controls through the existing grommet.

@SirLotus
I remember seeing a mention about a motor speed controller, but I haven't been able to find the link again. It looks like the motor could draw 12 amps/144 watts. I need to find a controller capable of that and then presumably use some small 1/4 watt resistors to replace the potentiometer that typically comes with the controller to get 3 speeds using the factory switch.
02-19-2013 06:58 PM
philethier bump
08-02-2012 07:21 AM
SirLotus Another, possibly more desirable method, is to route the three "speed" wires from the fan switch a desirable location and mount a solid state "motor variable speed controller" (VSC). Then route the single wire from the blower motor, as described above to the VSC.
Michael
07-25-2012 03:29 PM
hifiandmtb Yes, that is true...but it makes the whole area more airy :-)
07-25-2012 03:27 PM
SirLotus
Quote:
Originally Posted by hifiandmtb View Post
Yes, if you remove the clam grills, wheel arch liner & other covers, access throughout the front clam area is pretty good.

Here are some shots of when I installed a relay-switched Stebel Nautilus horn:



No need to remove wheel arch liners.
07-25-2012 02:57 PM
hifiandmtb Yes, if you remove the clam grills, wheel arch liner & other covers, access throughout the front clam area is pretty good.

Here are some shots of when I installed a relay-switched Stebel Nautilus horn:



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