Heater Core Bypass Mod (Tony Wa) [How To] - Page 3 - LotusTalk - The Lotus Cars Community
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post #41 of 340 (permalink) Old 07-31-2006, 04:27 PM Thread Starter
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3 hours?

The meat of the project (installing the valve and vacuum switch and bleeding the system) would likely take 1.5 to 2 hours. Plus maybe another hour+ fiddling with switch mount, running wiring, etc. A lot depends on whether you are comfortable enough to dive right in, or are moving cautiously......Once you get the valve in, you can go ahead and drive the car (finish the wiring/switch another time if you need to).

I was hoping to get a timeline when I modify the next car, which looks like it will be this Thursday. I'll post my time then.

Tony

Tony W.
05 Elise (Stage II, FrankIntake CAI, heater bypass)
04 MINI S (heavily modified)
06 IS350
69 Lotus Elan S4 SE - (orig black badge, weber, etc)
59 Austin Healey Bugeye Sprite (heavily modified, 70WHP)
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post #42 of 340 (permalink) Old 08-01-2006, 11:18 AM
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It sounds like Tony's mod along with some method to increase the volume of air at the vents would be a vast improvement. I'm anxiously awaiting some more reports from the first kit buyers, but I'm sure I'll be buying one.

2005 Elise: Laser Blue, LSS, Touring, HT, SS, Stage II. - SOLD
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post #43 of 340 (permalink) Old 08-03-2006, 04:28 PM
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Installed with Tony's assistance (actually he did most of the work). Nice car guy, BTW.

I think he has some pics of me upside down under the dash fiddling with wires and fuses.

After the install, I drove home around 8:00 pm, so not the hottest temps outside, but the A/C was running noticably cooler.

We added some Redline Water Wetter to the coolant. Seemed to knock a few degrees off my engine running temps. I had been running around 189 degrees on the highway, and it was averaging 183/184 degrees on the way home.

I will have to test the effectiveness of the bypass during the daytime when it's 98 degrees and humid out.

The install was clean and took us about 3 1/2 hours, but we also BSed a lot.

Incidentally, the temp of the firewall in the footwell run around 115+ degrees due to all the hot radiator hoses running through the area..
 
post #44 of 340 (permalink) Old 08-03-2006, 06:48 PM Thread Starter
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qball install

The install went very well and qball is right, we did bs quite a bit. I was also pretty tenative around someone's else's car so that added to the time as well...... but we did get it done with no incidents. I appreciate him letting me hack around in his car, that was brave (maybe not too bright).

Several updates to the installation procedures were made as a result of the items we ran into. Most notably is we found a much better place to pick up switched 12V power. But first I let qball lay in the passenger footwell upside down trying to sort our wires and fuses 1/2 inch from his face for 20 or 30 minutes. Just as he's gone in for the second dive, I find the switched power in the steering column (super easy access).....

See the picture.....he's much younger than me, so he'll survive. "the good of the many outweigh.......

I look forward to his feedback on the bypass.

I also agree that the Water Wetter keeps my car coolant cooler on average. It's slower to heat up at the lights and comes right back down when I'm moving.

Thanks again qball!

Tony
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Tony W.
05 Elise (Stage II, FrankIntake CAI, heater bypass)
04 MINI S (heavily modified)
06 IS350
69 Lotus Elan S4 SE - (orig black badge, weber, etc)
59 Austin Healey Bugeye Sprite (heavily modified, 70WHP)
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post #45 of 340 (permalink) Old 08-04-2006, 08:11 AM
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Quote:
Originally Posted by Tonywa28
Here's one technical update. I'm rethinking the auto thermostat switching. The problem I thought of was that if you're in bypass mode and you want to temper the AC output by adding in a bit of heat , you can't. You also couldn't run AC defrost and heat the car at the same time if the thermostat was tripped to switch the valve to bypass. So I think the final design is just going to be a 2-position switch that you set to bypass or not. The final design WILL incorporate the automatic return to the non-bypass mode when the ignition is turned off so the coolant pump circuit will operate as designed.
Tony
... probably a dumb question: rather than setting the bypass valve manually via a separate switch, couldn't this instead be activated automatically from the temperature control - i.e., heater bypassed when when temp switched to coldest setting regardless of whether AC is on or off?

-Chuck

"Fill what's empty, empty what's full, and scratch where it itches."

- Wallis Simpson, Dutchess of Windsor

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post #46 of 340 (permalink) Old 08-06-2006, 04:48 AM Thread Starter
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Smile Chuck - not dumb at all

This would be the best way to do it (temp switch position) and I think there is a separate thread going on on the board just for this possiblity. The complicated part (which I think you already understand) is the temp switch does not really have off/on postion (open or closed). Instead it is a potentiometer that varies the voltage over a range and moves a vent door in the climate system that let more or less air flow through the heater core to raise and lower cockpit temperate. 5 volts might mean half open while 11 means completely open and 2 volts means completely closed. It would be a relatively simple electronic circuit to drop the bypass above a certain temp switch voltage (would require a relay), I just got a bit burned out trying to work out he other parts of the kit. Maybe I'll go back and look at it now that the kit seems solid.
Tony

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05 Elise (Stage II, FrankIntake CAI, heater bypass)
04 MINI S (heavily modified)
06 IS350
69 Lotus Elan S4 SE - (orig black badge, weber, etc)
59 Austin Healey Bugeye Sprite (heavily modified, 70WHP)
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post #47 of 340 (permalink) Old 08-06-2006, 06:31 AM
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Well...was going to finish my setup...but my Audi air solenoid has very small leads. I can use generic push on connectors. c'est la vie.
After more thought..I think I'm just going to use my recirc button to control the bypass valve. THe recirc doesn't seem to do crap (in fact seems to make it worse). Does anyone know where the connector for the recirc comes out on the engine bay side?
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post #48 of 340 (permalink) Old 08-06-2006, 06:49 AM
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Quote:
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Does anyone know where the connector for the recirc comes out on the engine bay side?
I don't think it does. The recirc switch controls a stepper motor that closes the butterfly flaps to the fresh air intakes so that 90% of the interior air is recirculated to the blower fans. Recirc works on my car. Maybe your flaps are stuck.

'05 Storm Titanium / Red
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post #49 of 340 (permalink) Old 08-06-2006, 06:27 PM
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Tony, I suspect this may not be that simple. Air mixture flap is actuated by a stepper motor which I'm guessing is controlled by something other than a simple potentiometer. Unfortunately, what I know about stepper motors I can fit in a thimble and still have room for a bath. Any ee's out there?

-Chuck

"Fill what's empty, empty what's full, and scratch where it itches."

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post #50 of 340 (permalink) Old 08-07-2006, 02:43 AM Thread Starter
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recirc works?

Recirc also works? on my car, but it seems the footwell vents are above the passenger's feet....which means the recirculated air is drawn across the extremely hot firewall before it goes back into the climate control system right behind the driver's feet. So in my car the recirc actually performs worse than the fresh air intake to the AC due to the preheating of the air by the firewall....
Tony

Tony W.
05 Elise (Stage II, FrankIntake CAI, heater bypass)
04 MINI S (heavily modified)
06 IS350
69 Lotus Elan S4 SE - (orig black badge, weber, etc)
59 Austin Healey Bugeye Sprite (heavily modified, 70WHP)
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post #51 of 340 (permalink) Old 08-07-2006, 02:56 AM Thread Starter
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Lucksta - Blend Door Stepper Motor

Stepper motors do require some smarts as you mentioned. For the actuators I've personally seen (not many), these smarts are in the actuators themselves, not sure where they are in the Loti, but I'm assuming the same.

I know for sure that GM, Ford and Lexus products use a simple potentiometer for controlling the door actuator (some of the education I've gotten during this project). I believe the voltage read at a the various pot positions is sliced into "steps" and the stepper motor is moved in proportion to open and close the blend door. It would be good someone could confirm my assumptions.

I'll look into the one on Otis today or tomorrow.

Tony W.
05 Elise (Stage II, FrankIntake CAI, heater bypass)
04 MINI S (heavily modified)
06 IS350
69 Lotus Elan S4 SE - (orig black badge, weber, etc)
59 Austin Healey Bugeye Sprite (heavily modified, 70WHP)
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post #52 of 340 (permalink) Old 08-07-2006, 03:31 PM
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UPDATE!

Drove the car to work today. Car was nice and hot sitting in the parking lot with the top on.

Drove the expressway home (cruising speeds of 75 mph or so).

Had the bypass on the first half and it was nice and cool... Had the cool temp about in the middle of the blue on the dial, and the fan on #2.

Half way back, I turned the bypass off and I could feel the A/C vent air warmp up slightly after only a few minutes...

So bottom line is the mod works... even if it's 4-5 degrees it helps. Think if you setseyour house AC at 73 degrees how much colder it is then if you set it's set at 78 degrees

Qball
post #53 of 340 (permalink) Old 08-08-2006, 07:55 AM
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Quote:
Originally Posted by Tonywa28
Stepper motors do require some smarts as you mentioned. For the actuators I've personally seen (not many), these smarts are in the actuators themselves, not sure where they are in the Loti, but I'm assuming the same.
The physical actuator appears to be external to the air box, actuating the flaps via a control rod. From one of the diagrams in the Service Manual, it appears to be mounted to the left side of the front bulkhead (the crash structure mounts to the other side), near (in front of) where the heater core is located.

From the electrical diagrams, I can't tell where the "smarts" for the stepper motor is located - but it does appear that the circuit is handled by the "switch pack". From the Service Manual:



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post #54 of 340 (permalink) Old 08-08-2006, 11:11 AM Thread Starter
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Bypass Switch Answer - Woo-Hoo!!

ET,
I think I've found a good solution for the heater bypass switch that retains the completely stock appearance of the switches (heck it IS stock plus a hidden function). The existing temp control is a 10K linear potentiometer. What I did was just look for a 10K linear pot with an integrated on-off switch. These are plentiful. I saw 200+ today at the local electronics surplus place (Skycraft in Orlando). There are multiple type of shafts, switches, etc. What you're looking for is one that has the on-off with contacts closed at the most counter-clockwise position (coldest setting). What this does is turn on the bypass only when the temp pot is at it's coldest position. As soon as the knob is twisted clockwise (hotter), the bypass is switched out and the heat works just fine. This project does require a bit of soldering and filing, but nothing very fancy at all. NO electronic component work, just unsolder and resolder 3 wires and run two wires to the new switch (which you have to do for the bypass anyway). I actually used a pot with a push-pull switch, so when you want bypass, you just pull it out a bit (til it clicks), when you want heat, push it in and turn up the temp. I think the pot I described at the top is cleaner and more intuitive, I just couldn't find the one I described in the surplus store.

I just installed it today and it's working great. Bone stock look. See pix for details of install. Not too tough at all! Threading the wires through the dash was the most aggravating part....

Specs: 10K linear pot with integrated on/off switch that is normally closed in fully counter-clockwise postiion. 1/4 flat shaft (not just D-shaft, but 1/2 of the material gone from the shaft.
Ah, the end of the road for the bypass design....maybe.
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Tony W.
05 Elise (Stage II, FrankIntake CAI, heater bypass)
04 MINI S (heavily modified)
06 IS350
69 Lotus Elan S4 SE - (orig black badge, weber, etc)
59 Austin Healey Bugeye Sprite (heavily modified, 70WHP)
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post #55 of 340 (permalink) Old 08-08-2006, 11:51 AM
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Tony, that's awesome! I admit, I was totally skeptical about the temp knob controlling the bypass, but I never thought about a pot with an on/off function. You deserve some sort of award for your work.

John

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post #56 of 340 (permalink) Old 08-08-2006, 02:51 PM
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Quote:
Originally Posted by Tonywa28
What I did was just look for a 10K linear pot with an integrated on-off switch.
Very clever! This would be my preferred implementation.

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post #57 of 340 (permalink) Old 08-08-2006, 05:17 PM
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Wow...I'm glad I'm being lazy. Tony that was a brilliant idea. Is this a part one can get from Rat Shack? If not, I'll just pay you to ship one to me to save me the hassle
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post #58 of 340 (permalink) Old 08-08-2006, 05:19 PM
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I want a refund!

Just kidding. My hidden switch is unnoticable!
post #59 of 340 (permalink) Old 08-08-2006, 05:27 PM Thread Starter
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Kits available

I think I have enough feedback to let the kits loose on the public. Those of you who have sent me an email should be getting an update now.

Prices are $90 for basic kit, $10 for Temp switch upgrade, 3 for basic switch, $12 for Water Wetter (cheaper if you buy it locally).

If anyone else is interested or didn't receive the update, email me at

[email protected]

I'll be doing 3 more installs on Orlando cars in the next week or two, but I'll be getting out of the install business soon...

New Instructions will be posted in the next day or two.
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Tony W.
05 Elise (Stage II, FrankIntake CAI, heater bypass)
04 MINI S (heavily modified)
06 IS350
69 Lotus Elan S4 SE - (orig black badge, weber, etc)
59 Austin Healey Bugeye Sprite (heavily modified, 70WHP)
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post #60 of 340 (permalink) Old 08-08-2006, 05:47 PM
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Tony, instead of a push/pull, would it be more likely to find a pot with detents that had a on/off position at the far range of travel?

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16 Honda CR-Z EX
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