HVAC Fan Resistor Pack Bypass is Successful! - LotusTalk - The Lotus Cars Community
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post #1 of 84 (permalink) Old 06-10-2012, 07:45 PM Thread Starter
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HVAC Fan Resistor Pack Bypass is Successful!

From the idea BlackSix posted and with lots of help, calls and coaching from SirLotus, I successfully bypassed the dead resistor pack today. THe entire process took me about 4 hours. I believe a well prepared person with a ready helper (who is ideally about 4'2" with small but strong hands) could accomplish what I've done in a couple of hours. I'll walk through the thought process and the procedure. I took a few pictures but because of the location, they aren't great. They should help with context at least.

If you frequent this section of the forum, you understand that tragic design of the HVAC Fan Resistor Pack. Putting the resistor at the bottom in a sealed pan just doesn't even remotely make sense but we didn't buy these cars for practicality. I called the local dealership. I was quoted $495 for a new fan and resistor pack and was told that's the way its done....replace them both. Total estimate to pull the clam, clear the freon, remove the A/C, replace the freon and reinstall every thing was $1800. And, oh yeah, the parts won't be in the US until mid-July! I live in Dallas. With my daughter home for the summer, the Lotus is a daily driver.

I then went to a local Lotus service guy. He was really helpful but just said "you can do it....it won't be hard". While I think I could, I was kind of dreading pulling the clam as I'd be doing it alone. The fear of scratching the car or having one dang bolt left over was tough.

SirLotus and others can explain this better but the idea posed was whether one could access the proper wires through the footwell firewall, splice in, route the wires and connect them to the switch. SirLotus wasn't aware that anyone had tried this. I was an easy mark.

What we are trying to accomplish is to bypass the resistors. I'll be cutting the orange power wire that ran to the motor and connecting it directly to the #3 position on the rotary knob. This means I'll have either off or full blast on. If you own one of these cars and if you live anywhere that actually requires AC, you know that we really only have 2 positions - off or full speed.

(This does bring up the ethical issue of not keeping the car stock. And I'm clearly making the car "less functional". I rationalized this in many ways. 1) I don't want to spend $1800 for what should be a $300 job 2) I'm a little leery of pulling the clam 3) I just know as soon as I spent $1800, I would immediately get hit or be in an accident which will require someone's insurance company to pay for removing the clam. And when that happens, I'll replace the motor and pack and go back to bone stock. If this is sacrilegious to you, read no further.)

Here's the view of footwell to start:



Step 1: Remove the Driver's side seat. You need all the space you can get. There are 2 13mm bolts at the front of the rails and 2 6MM hex head (allen head) bolts at the rear. There is a 17mm (use open end wrench) bolt which holds the seat belt to the seat. Once all free, carefully remove the seat. Its easy to scratch stuff with the sharp rail ends. I forgot about the "fasten seat belt" wires but they conveniently just pulled apart. If you want to be more careful, once the seat rails are free, rock the seat forward and reach under. But cover the front of the rails so they don't scratch the extruded cross-wire aluminum (that the rail bolts into).



Step 2: with a Sharpie, trace around the plate which covers the vent holes. You need to know where to cut.



Step 3: Remove the plate covering the 5/16" perforations. Select a drill bit slight larger than the hole in the rivet and drill them out, I used one that measure at .187" and it worked fine. Drill out all 4 rivets and remove the plate.

Step 4: Make an access port by cutting on the traced line. I used a Dremel tool with metal cutting wheels. Note: I initially didn't have the 90 degree adapter for my Dremel. Because the Dremel is relatively long, it was difficult to work. I went through the 6 cutting wheels I had quickly. Home Depot didn't stock this adapter but Lowe's did. It was $30 plus I bought another 10 cutting wheels (~$10 for 5).



Once I had the adapter, the quality of my cutting improved dramatically.

A couple of points to be made here.

1) Initially, I was thinking I would cut this neatly and when done, just silicone glue it back into place. As you can see below, what I did was simply not clean enough to do that. I'll be looking for someone to fabricate a new plate with perforations that'll I attach over this hole to clean up the appearance.



2) IMPORTANT: We knew there was some level of structural bracing running through the area but not sure where. It turns out that if you cut more than about 1/8 below the bottom line, you'll start cutting this bracing. I believe if you didn't know better, you could do this. If you start with a side or top, you'd know what cutting through one layer is like versus cutting the structure. Not only is it harder to do, you really don't want to do that! (Note I did nick mine but it won't be a problem. - see the red adhesive on the picture.)

3) Because I wasn't exactly sure what was behind this, I went through some level of pains to tape from the back and front of the perforated plate I was cutting so it couldn't fall in. I suppose it could and be a little challenging to remove, I'd say this is optional.

4) Once you remove the plate, immediately tape up the exposed edges with painters or duct tape. Otherwise, you WILL cut yourself.

Step 5: You can see the fan! You also can see that the fan is recessed about 5 inches, making it harder. The bent panel in the footwell on the passenger side partially covers perforations like the previously completely sealed perforated panel on the drivers side. These are both "cold air returns" or how the cold air in the cabin is recycled or recirculated. The air that comes in from the passenger side flows toward the drivers side in the chamber that the fan motor is attached. Hence the reason for depth.

Hopefully, you can see a couple of wires one each orange and black. The circle around the motor itself before taking a radius out. On my car, the orange wire started at about 9:00 and the black started at about 12:00. They circled counter clockwise behind the structure veins of the fan (closer to you then the squirrel cage itself) and go down at about 5:00. If you look closely, you can just make out a small wire tie on this vein.



Your goal now is to get as much slack as possible in the orange line. Remove the wire tie. Try to separate the orange and black as much as possible. You do NOT want to cut the black (ground) line. It stays.



With your wire cutters, reach down and far as you can - even into the foam seal - and cut the orange wire. And now would be a good time to pray that the resistors are actually what your problem is.

Push-feed the wire back under the veins at 5:00, 7:00 and 8:00 and then pull the orange towards you. If yours is like mine, the wire comes within about 1" from actually being accessible. Mine did not leave the cavity.

Step 6: Find your favorite little person now. I somehow got my wife to help (pathetic look on my face). She wasn't real pleased about being in a confined space with sweaty me from 4 hours in the garage at 95 degrees.

I bought a 12 foot section of 12 gauge AWG wire from Autozone and some 12 gauge butt connectors. Put a butt connector on the 12 gauge wire. Then, while holding the orange wire steady, insert the 12 gauge with butt connector through the opening, simply slide it on the orange wire and just crimp it in place! This step took me about 45 minutes to realize it was simply impossible to do by yourself. Not only did I need her help but she also had the good idea (after about 20 minutes) to grab a couple of hemostats to add in holding.

It worked! Candidly, the orange wire had about 1/8 inch wire exposed beyond the butt connector. I don't know if I had too much striped or not but the connection withstood a reasonable tug. I smeared the exposed part with RTV and encased the whole thing with shrink wrap.

Happened that Michael (SirLotus) called to check on me at that time. He immediately suggested that I just jumper it to the positive terminal on the battery. We then virtually celebrated as the fan turned on.

Step 7: Courtesy of Michael's knowledge, I then pulled the HVAC control panel out and pulled the plugs off the terminals for the the green/gray and green/blue. These control positions 1 and 2. I don't think it would matter but I pulled them because Michael told me to!.



I then unwrapped a little piece of tape holding these wires so I could cut the green/yellow (#3 or full speed) wire. I choose to insert a male/female plug there.



Check it all - still works - and I'm done for the time being.

2 problems remain:

1) I have to do something about the hole in the fire wall. I know what I want - does anyone have access to a machine that could cut a word or design into a piece of 1/8 aluminum?

2) I've got to figure out how to run a wire into that HVAC controller area. Right now, I just have the 12' of wire balled up and sitting on the parcel shelf. I'll be posting to look for help on that next.


Thanks to BlackSix for proposing the idea and serious thanks to SirLotus for talking me through this (talking me into this!). I can assure you that he spent more time working on this than I did. This is when the forum really works - good people willing to help. I hope this write-up helps someone else. I'll review and edit later.

Scott
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post #2 of 84 (permalink) Old 06-10-2012, 08:24 PM
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Fantastic! As somebody who has done this the hard way, i applaud your effort. You can easily get a panel water jet cut with whatever design you like for not too much.

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post #3 of 84 (permalink) Old 06-10-2012, 10:40 PM
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This place rocks! One of the best technical write-ups I've ever seen.

And yes, I know how damn horrible it is working under the dashboard...people don't fit down there.

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post #4 of 84 (permalink) Old 06-10-2012, 11:10 PM
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Interesting. I'm gonna pull the clam this winter most likely. Don't need a heater when I have the car out anyhow, but it'd be nice to have A/C once in a while I suppose.
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post #5 of 84 (permalink) Old 06-10-2012, 11:12 PM
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Interesting repair. I'm afraid I couldn't bring myself to cut the sheet metal in that area, even if it is perforated. I wouldn't want someone else to see what I'd done ... but that's not my point ... here are a couple of ideas about the tools you used.

When drilling out pop rivets, use the same size drill as was used to install the rivet. In your case - those look like 1/8" rivets - I would have just drilled the heads off with an 1/8" drill. Stop as soon as the head spins off on your drill - there's no need to drill any farther. The pop rivet body can usually be pushed out the back with an awl or a pin punch (or if you have access, pulled off with pliers). This leaves a correctly sized hole for the same rivet size when you replace it.


Abrasive parting discs are my last resort for cutting thin sheet metal - they are a dicey proposition at best. A much easier tool for cutting sheet metal in your situation would be a nibbler. It goes into a hole or starts at an edge and takes a small square or rectangular bite out of the sheet metal without distorting either side of the cut. Take successive bites to cut along a line. This tool comes in both pneumatic/electric or hand-powered versions (I'd stay away from the drill motor attachments though). The hand-powered version would work fine (albeit a little slow) for your application. It's a very handy tool - especially for blind cuts in the middle of a panel like yours.

Glen

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post #6 of 84 (permalink) Old 06-11-2012, 01:47 AM
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it seems like you can still use the number 1 and number 2 fan speed by using this diagram. using your tap wire from the motor, use in-line splice ( which is black wire 12 gauge you used, orange/red wire on the diagram ) red wire for number 2 and yellow for number 1 at slow speed. but you have to cut the existing wire which is green/gray and green/blue like you did on green/yellow. pictures are from rob13572468.
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post #7 of 84 (permalink) Old 06-11-2012, 03:08 AM
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Quote:
Originally Posted by jlotusd View Post
it seems like you can still use the number 1 and number 2 fan speed by using this diagram. using your tap wire from the motor, use in-line splice ( which is black wire 12 gauge you used, orange/red wire on the diagram ) red wire for number 2 and yellow for number 1 at slow speed. but you have to cut the existing wire which is green/gray and green/blue like you did on green/yellow. pictures are from rob13572468.
Firstly, I want to applaud "Yellowvert" for attempting this repair and also taking the time to post his experiences.
Actually the location of the resistors is important. Due to the heat they generate, they have to be placed in constant moving airflow. This is the reason for the factory location. Another alternative is to install a solid state electronic variable speed 30A DC motor controller Motor speed controller. This unit can be installed anywhere as it does not generate high temperatures like the resistors.
Michael

Last edited by SirLotus; 06-11-2012 at 03:21 AM.
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post #8 of 84 (permalink) Old 06-11-2012, 04:53 AM Thread Starter
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Thanks all. I will likely be doing the DC motor install as SirLotus suggests. Heck, he got me this far but its a lower priority than figuring out how to fish the wire in place. I noticed a whole lot of typos in this write up. Someday, I'll clean that up but last night I was more interested in getting this posted while it was fresh in my mind and drinking a couple of IPAs then doing much proof work...
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post #9 of 84 (permalink) Old 06-11-2012, 05:00 AM Thread Starter
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Quote:
Originally Posted by Glen View Post
Interesting repair. I'm afraid I couldn't bring myself to cut the sheet metal in that area, even if it is perforated. I wouldn't want someone else to see what I'd done ... but that's not my point ... here are a couple of ideas about the tools you used.

When drilling out pop rivets, use the same size drill as was used to install the rivet. In your case - those look like 1/8" rivets - I would have just drilled the heads off with an 1/8" drill. Stop as soon as the head spins off on your drill - there's no need to drill any farther. The pop rivet body can usually be pushed out the back with an awl or a pin punch (or if you have access, pulled off with pliers). This leaves a correctly sized hole for the same rivet size when you replace it.

--I'm sure your right on this. Since I didn't care about quality, I just tried a couple until the head popped on the drill bit. It'll get covered at some point.

Abrasive parting discs are my last resort for cutting thin sheet metal - they are a dicey proposition at best. A much easier tool for cutting sheet metal in your situation would be a nibbler. It goes into a hole or starts at an edge and takes a small square or rectangular bite out of the sheet metal without distorting either side of the cut. Take successive bites to cut along a line. This tool comes in both pneumatic/electric or hand-powered versions (I'd stay away from the drill motor attachments though). The hand-powered version would work fine (albeit a little slow) for your application. It's a very handy tool - especially for blind cuts in the middle of a panel like yours.

Glen
-- I wasn't real happy about this either. Lots of nasty dust, fear of the disk flying apart, etc. I'm not aware of this tool but will look into it for future use.
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post #10 of 84 (permalink) Old 06-11-2012, 01:06 PM
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ALCON,

Thanks for the awesome write up - I am 2 years without A/C or heat and I am ready to try this solution - I will need to review the post for a list of tools and necessary parts for the job.

This is really really cool - I plan to do this in couple of weeks - may need to reach out for help but I am so ready for A/C during the eastern North Carolina summer -

The Lotus is fun at the beach but the 3 hour drive in 95 degree heat is painful.

Thanks to all -

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post #11 of 84 (permalink) Old 06-11-2012, 02:47 PM
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Great write up ! Thank you.
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post #12 of 84 (permalink) Old 06-11-2012, 03:37 PM
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I am going this route also. My question is do we really need the opening this wide anyway.
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post #13 of 84 (permalink) Old 06-11-2012, 06:43 PM
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Thank you yellowvert for trying this and it being succesful and blacksix for the idea and sirLotus for help. Then also documenting and sharing with us.

On pic 1 there's the solid alum panel thats held by the 4 rivets.
If one was to cut the opening smaller; an area within the 4 rivets just along the perforated air holes in pic 3, then maybe the solid alum panel can just be riveted back in place, or use some type of screw/bolt for easier access in the future? Then discard the piece with ventilated holes? Is this possible, and any harm in discarding the cut out piece with perforactions

Last edited by rcuser; 06-11-2012 at 06:54 PM.
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post #14 of 84 (permalink) Old 06-11-2012, 07:04 PM
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Thank you yellowvert for trying this and it being succesful and blacksix for the idea and sirLotus for help. Then also documenting and sharing with us.

On pic 1 there's the solid alum panel thats held by the 4 rivets.
If one was to cut the opening smaller; an area within the 4 rivets just along the perforated air holes in pic 3, then maybe the solid alum panel can just be riveted back in place, or use some type of screw/bolt for easier access in the future? Then discard the piece with ventilated holes? Is this possible, and any harm in discarding the cut out piece with perforactions
It is advantageous to remove both footwell solid panels to improve the HVAC performance by increasing the airflow. https://www.lotustalk.com/forums/f313...-system-71031/
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post #15 of 84 (permalink) Old 06-12-2012, 06:53 AM
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^^I see now

I wonder if one can access the orange wire going to the resistor and have enough slack/access to crimp it to the main red wire going to the blower. It's tight down there and not sure if a hand could even get to the resistor pack via feel.

This would avoid routing a 12awg wire to the HVAC control knobs, right?
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post #16 of 84 (permalink) Old 06-12-2012, 06:59 AM
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^^I see now

I wonder if one can access the orange wire going to the resistor and have enough slack/access to crimp it to the main red wire going to the blower. It's tight down there and not sure if a hand could even get to the resistor pack via feel.

This would avoid routing a 12awg wire to the HVAC control knobs, right?
We had considered this, but came to the conclusion, that it was next to impossible.
Michael
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post #17 of 84 (permalink) Old 06-12-2012, 07:27 AM
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^^thanks, shucks it would have been nice for a clean repair
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post #18 of 84 (permalink) Old 06-12-2012, 09:28 AM
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Thanks for the write up on this, nice to have a proven option to removing the clam. I don't think you need to cut the opening quite that wide to access the red wire. My solution for finishing everything up and having a factory look with increased airflow and maybe keep some of the debris out of the fan area... I used the same plate from the passenger side ordered from lotus garage held with plastic rivets, works great looks good.
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post #19 of 84 (permalink) Old 06-12-2012, 09:49 AM
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Thanks for the write up on this, nice to have a proven option to removing the clam. I don't think you need to cut the opening quite that wide to access the red wire. My solution for finishing everything up and having a factory look with increased airflow and maybe keep some of the debris out of the fan area... I used the same plate from the passenger side ordered from lotus garage held with plastic rivets, works great looks good.
Even the partial passenger side plate restricts air appreciably. It makes sense to cut all the way around the perforated air return rather than cut across holes, leaving jagged edges.
Michael

Last edited by SirLotus; 06-12-2012 at 11:17 AM.
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post #20 of 84 (permalink) Old 06-12-2012, 10:14 AM
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Thanks for the write up on this, nice to have a proven option to removing the clam. I don't think you need to cut the opening quite that wide to access the red wire. My solution for finishing everything up and having a factory look with increased airflow and maybe keep some of the debris out of the fan area... I used the same plate from the passenger side ordered from lotus garage held with plastic rivets, works great looks good.
it looks clean, What did you connect the red wire to? how did you route it? thanks
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