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JnC said:
I may be making a bad assumption, but if the water in the heater core loop is as hot as the water in the radiator loop, wouldn't you be cutting the amount of hoses running hot water by half?

Or is the amount of heat generated by the engine now fully transferred to the radiator loop, and the net dissipation from hose to chassis hardly changed?
I think that you have it right in the second part - there is still a total amount of heat that will be transfered to the front of the car. You would save a little bit of surface area of warm pipes that radiate heat, but not much. Additionally, the radiator pipes are much larger in diameter than the heater pipes. I don't think it would make a noticeable difference in sill temperatures if you bypassed at the engine instead of up front. But you'd have to actually do it and measure it (or do an awful lot of calculations) to know for sure.
 

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Those people with the early "non-pre-wired" cars that added the Driving Lights now have a good use for the three switch panel and extra switch (probably need a relay though).:)
 

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Tonywa28 said:
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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Pete k said:
It can't be engine cooling, it seems to me the recirc pump is just to get water to the heater core in a hurry on a cold day.
Nope, the recirculation pump is controlled by the ECU. After you shut down the engine, the ECU monitors the temperatures for about 20 more minutes. If it detect that things are "heat soaking" then it turns on the electric recirculation pump to circulate water through the head to the heater core. This prevents localized hot spots.

What is not known is how much heat removal is done by the heater core, verses the lines up to the front and back again. In any case, that is the reason for the vacuum controlled valve - when the engine is turned off, the valve go out of "bypass mode" and water is again circulated through the heater core.

Making it a manual bypass valve by the engine, would defeat the purpose of the recirculation pump. Even making it automatic (like the vacuum operated on valve) might cause problems with "cold" water from the bypassed heater circuit is suddenly recirculated into the cylinder heat. That's why the bypass valve is mounted up front - all it is removing from the circuit is the actual heater core (removing it as a heat source in the HAVOC box).

It would be possible to put a manual valve in the vacuum line to turn off the bypass in the winter, and make it automatically come on in the summer if you wanted to save the effort of doing the electrical wiring. But I would think that the on-off switch would be worth the effort.
 

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pete k said:
TI have never heard it come on, and probably won't.
I've never heard mine come on either. But then again, I have yet to wait around for 20 minutes listening for it either. I suspect that it must be a distinct possibility that it can be needed, or Lotus wouldn't have gone to the trouble to have installed it on the car. I believe that someone had simply disconnected their heater by replacing the hoses at the engine with a short one to interconnect the in/out at the engine.

I like the safer way of mounting the bypass up front - keeps the recirculation pump/system for heat soak, and should prevent thermal shock (even if that isn't a serious problem).

But there is not reason that you couldn't use an electrically controlled valve like you figured, and mount it up front. Or use a vacuum controlled valve with a manual on/off valve as I posted above...
 

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Tonywa28 said:
I can remember updating my Elan with nice shiny big tubular a-arms over the original stamped steel channels because I thought strong and heavy was always good. Then a revered Lotus tuner pointed out that now any curb impact that I had was going to send the shot straight to the stressed skin frame rather than the original a-arms sacrificing themselves.....much more expensive proposition to replace a frame than replace a-arms...Chapman was a genius
As another Elan owner, but one that had an idiot pull out in front of me from a stop sign and take off the left front corner of my Elan, I can attest to the wisdom of this. My front tire/wheel was pushed back, and a couple of a-arms buckled, but my frame was completely undamaged. The a-arms were cheap to replace...
 

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Keeper said:
So, you can switch the bypass in and out? I guess I should have taken a closer look at the instructions. It's been a long time, but I thought if you did this mod your heat was gone.

Also, it sounds like the bypass automatically shuts off when the car shuts off. Is that true?
Tony's kit uses a vacuum controlled bypass valve to "shut off" the heater core. When you turn off the engine you loose vacuum and the heater is no longer bypassed. This is good, because the Elise has a coolant circulation pump that can turn on to circulate coolant through the head to lessen heat soak - this turns on automatically (as needed) after you shut down your engine (and walk away from the car). The coolant circulates through the heater system to "vent" the heat.

The vacuum bypass valve is controlled by an electric switch. When off, there is no engine vacuum supplied and the heater is not bypassed. When on, the vacuum is passed to the valve. Nice clean system to reduce the heat soak of the heater core that causes warm air to always blow out of the vents.
 

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a) The light switches that come with the car are MOMENTARY. The logic is controlled by a computer. The switch just provides a momentary pulse of input.
Yes and no. The head and parking light switch are momentary, as is the AC switch.

However, the switch used for the installation of the factory Driving Lights is an on/off switch, not a momentary. One of them could be used...
 

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Fred Zust sent me one...it is a momentary switch, pretty sure after testing. See my other threads about switches for a possible solution suggested by jim-clayton..
Well, I've tested my driving light switch, and it is definitely not momentary. Others have accidentally swapped headlight and driving lights switches when installing the driving lights, and discovered that things don't function properly until they swap them back around and put the on/off switch on the driving light circuit.

The factory driving light switch IS NOT a momentary switch.
 

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Interestingly enough, the wiring diagram definitely shows the headlight and parking light switches as maintained (on/off). However, what is not shown, is the logic circuitry in the switch pack module, that could very well mean that these switches are momentary.
Well, if you think of how the headlight switches work, it becomes apparent that they are momentary and the logic is in the switch pack module.

If you push the parking light button, the parking light turn on. Pushing it again turns them off.

Now, push the head light button. The head lights and the parking lights turn on. Push it again, and only the head lights turn off. You have to turn off the parking lights by pushing the button (that you didn't push to turn them on). The parking light switch is not "latching" in an on or off position.

The only way the above works is that they parking lights switch has to be a momentary switch sending a "signal" to the the switch pack module. Since both the parking and head light switches are the same, they are both momentary (Also this has been confirmed by people that have accidentally switch them when installing the driving lights).

If I remember correctly the AC button works similar. If you push the button without the fans on, nothing happens. Turn on the fans, and then the button and the AC turns on. If it was a latching switch (on/off switch) then pushing the button should leave it in the "on" position and the AC would turn back on if you turned on the fans. Additionally, if you have fans on and AC on, the AC on is canceled if you turn off the ignition, then turn it back on. Again, it's a momentary switch.


Now, the function of the driving light switch does "latch". Push the button, and the driving lights come on with the high beams. Turn off the head lights and/or the ignition, and when you turn the high beams on again, the driving lights will be on. That switch "latches" - on or off - and stays that way untill you push the button again.


And again, it's all been tested by people with multi-meters to check continuity... ;)
 

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FYI - Here's some other applications for that solenoid (as listed by RockAuto):
So basically, every Chevy/GMC "truck" made in the last 20 years... :D
 
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