Interior Exterior
Q:
Mine works fine but I've only had the car for 9 days. I tried it on the drive home and the few times I've had it out. I will post again when it's warmer and the AC will be put to a real test.
ok, i am wondering about something...i heard it's actually good to turn your AC on at a regular basis because the o rings in your system will get brittle if you don't. The freon contains lubricants which help condition your o rings and keeps your system in good shape. If you don;t turn on your AC then those ubricants do not get to condition the selas that keep the freon in and thus, you increase the chances of getting a leak. Anyone else hear of this.
I do this on my daily cars, a 96 4Runner and a 97 Camry. Especially during the winter time I would have the heat on and just hit the AC button and leave it on for like 5 minutes once a month. Both cars and not had one leak in thier AC systems.
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Tim,
I understand the purpose of the recirc after shutdown to avoid hotspots (as you correctly pointed out), but if the heater is bypassed (not blocked), it seems to me the recirc would still do the job of avoiding pockets of heat (water is still circulating) and that the loss in efficiency would be the amount of heat the heater core could reject during the 20 minutes versus just circulating the water through the tubing still remaining in the circuit. So why I agree the hot spot protection may not be as robust, I believe it still exists (assuming that enough heat is dissipated in the first 20 minutes without the heater core, and I feel it would be - IMHO). I'd be happiest with a switchable bypass valve that would always flow through the heater core in the power off position.
I would not do a track day ever with the heater bypassed.
I have been trying to look around for in-line blowers to boost the fan flow, but most all are 4" in diameter and a few 3", but no 3.5" so far (3.5 ID is what the tubing is in the car). One last note, I took off the 3.5 " vent hose between the evaporator and the manifold under the dash (where the air is divided up into the various outlets in the car) and ran the fan and was very surprised at the output. Reaching into the AC manifold inlet to feel around revealed a fairly restrictive opening, so I'm wondering how much of the problem is in the restrictive air passages....
Let's keep after this one, PLEASE. It's hot down here in sunny central Florida!!
Tony
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and that the loss in efficiency would be the amount of heat the heater core could reject during the 20 minutes versus just circulating the water through the tubing still remaining in the circuit.
From what I understand, the bypassing is done at/near the engine. The circulation pump through the heater also causes the coolant to flow through the hoses/pipes in the sill through the heater and back through the other sill - this would add to the heat dissipation, if only because it would be circulating additional coolant.
But the idea of an automatic bypass valve that would revert to routing through the heater system when the ignition was off would seem to be a good way of doing it - the best of both worlds.
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this is exactly what the dealer tech in austin suggested. using a heater bypass valve near the heater ocore upfront. Something like a ford or chevy part using a electronic switch hooked into the a/c switch. if anyone tries it please share the how. I have bypass my heater core and the a/c is wonderfully cool in 100 degree heat. I would not track the care like this though. I happen to park the care in garage at all times, garage at home and at work. the motor temp never goes over 195 even when parked.
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The water circulating through that heat-soaked heater core can't be doing much. When does the pump turn on? It is temperature activated? I have never seen my temp gauge over 202. I was at the track yesterday in 96 degree heat. Ran 5 ..... 30 minute sessions. Max temp was 198.
Having 200 degree water running next to your ac vent / fan is not "cool".
Bypassing the heater core was the cure to my AC problems.
No more sweating the South Florida heat.
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The water circulating through that heat-soaked heater core can't be doing much. When does the pump turn on? It is temperature activated?
Yes, it is temperature activated. The ECU monitors the temperature for something like 20-30 minutes after the ignition is turned off and it turns on the recirculation pump as necessary.
It's not just the overall temperature of the system, it is the heat soak after the engine is turned off. Basically, when you turn off the engine, the hot spots in the engine are still transferring heat to the coolant. Even if the temperature at the thermostat (or temperature sensor displayed to the dash) is acceptable, local spots can get very, very hot - especially in the enclosed engine compartment of the Elise where the engine is not as free to radiate heat to the surrounding air. That's the purpose of the recirculation pump - it keeps moving some of the coolant through the head/engine and spreads the heat around. The heater core may not be able to radiate off the heat all that well, but just the moving of the coolant through things helps, and the larger the volume the better.
Now, that said, I've never heard my recirculation pump kick on - then again, I haven't hung around the car to listen for it either. There must have been some reason that Lotus added it to the car.
The idea posted a couple of posts above would be a great solution - an electrically activated shutoff valve that would bypass the heater when the engine was on, but revert to passing through the heater when it's turned off. But you would probably want the valve up front near the heater core instead of in the engine compartment, otherwise you might end up with "cold" water being recirculated into the hot engine.
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yes, exactly, the lotus tech said the valve should be in the front compartment next to the heater core where the bypass should also be without it. He said that any bypass of the heater core should be upfront and that they pictures we have on this site are good directions.
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I've spent several hours online and a couple of trips to the local commercial parts warehouse to look at heater control valves. All I found (looking through multiple catalogs) are vacuum or cable operated. No electrics. If somebody finds one, please let me know. Nobody at the warehouse had ever heard of an electric one. I did sort of see one in an automatic climate control system for European buses, but couldn't get a quote or even a civil reply when I inquired. I'm sure it would have been many $$. Looked at a lot of motorized ball valves and solenoid valves, but they also are $$$ and few accept 12VDC (mostly brass, all look heavy). I have started down the path of using two of the cable models that I will tie together and drive with a tiny gearhead motor. If anybody is interested, I'll take some pix along the way to share.
I have a question for the thread - when should the bypass be "bypassing"? If you tie it to the AC Dash switch, then you still get hot air in the vent mode. If you make it a separate 3 position momentary switch (think Winter-Off-Summer), then the fall back to "no bypass" is lost. The circuit would be simple, but would rely on the skill and memory of the operator. The automatic no-bypass feature could be made to work if you have a standard (non-momentary) 3 postion switch, but would require some fancy work to switch off the valve drive when the valve limits are reached and would require more circuitry. Heck, you could even tie it to a cable and change it all you want....Opinions and suggestions are very welcome.
One last item, I have a bit of concern that the bypass circuit will not have the same in-line restriction as the heater core. Water flow, like current will take the path of least resistance. This is not a concern with the engine off, but with the engine on and running. We may be changing the flow rates to other parts of the engine/radiators. I'm thinking of putting some restriction in the bypass loop to address this.
Sorry so very long, but I'm self tortured by all my bad solutions....
Tony
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Hooking a vacuum controlled one up would be easy. If you can find one that has the right connections, I could tell you what you need to do the vacuum controlled one.
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My friend did it on a c5 vete, just a couple 1/4 turn ball balves (brass body, stainless ball, teflon seat). He also did it on his old truck, it still has a gauge in the vents from years ago. Blows 25 degree in Arizona.
I just checked mine tonight at 6pm, blew 58 degrees.
The black dash sucks it up the sun like a solar colector and makes the car hard to cool. Put your hand on it during the brightest time of day. My ZR1 had a special film in the windshield to keep some wavelengths for going thru. The ZR1 had a smaller compressor so this was GM's fix.
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Rob,
Is there already vacuum in the front of the car somewhere? I didn't look for vac up front as I couldn't think of anything that would likely be using it. Finding an appropriate vacuum based valve should be no problem at all. What about switching? I don't know much about what's available to switch vacuum units off and on (electric solenoid valve?)
I looked at the 3-port brass ball valve fittings route. I've used that on something similar (oil cooler/accusump) in the past. I was trying not to use it this time paritally due to weight, but the bigger issue was that the required 12VDC actuators were very pricey (also big and heavy). It was going to be well north of $200 for the valve/actuator. It is certainly a workable solution for manual control. Probably in the $30-40 range, but for about the same money you can use the cable driven plastic composite valves sans cable. They are cheap, light, reliable and built for this purpose.
I'm going to carry on working the automation quest (saddle up the donkey, Sancho).
Wordy again.....sorry
Tony
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tony, please send pix and parts of any solution you develop. I am very interested and think that a simple summer on twisty valve will work just fine. anything to avoid getting all the way into the heater box area and switch hoses around dumping fluid in the chassis would be better than that.
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You don't need to hook the bypass up at the front of the car. You can connect it at the rear.
All you need is bypass valve that has 4 ports, so you when you bypass it recirculates still within it's smaller closed system.
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First weather hot enough to use it, and to my dismay it was the coldest AC than eny other car I've owned.
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Here is a diagram. The heater circuit has it's own plumbing routes. Crafting a bypass that works with engine vacuum would be excellent. I could design it so it kicks on when the AC is on, and shuts off when the AC or car turns off.
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Bypassing the heater core was the cure to my AC problems.
How much coolant pours out when you disconnect the hoses?
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Here you go....an electric version.
http://cgi.ebay.com/FORD-HEATER-VALV... QcmdZViewItem
FORD HEATER VALVE
TO FIT FORD FIESTA 96-2001 (MK4/MK5)
FORD PUMA 98-2005 (ALL MODELS)
FORD KA 97-2006 (ALL MODELS)
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Late to the party, but I have said from day one, it has worked pretty well each time I used it.
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You don't need to hook the bypass up at the front of the car. You can connect it at the rear.
All you need is bypass valve that has 4 ports, so you when you bypass it recirculates still within it's smaller closed system.
The longer you can keep the loop the better. When you DO finally open the valve, you want the volume of cold water reentering the system to be as small as possible.
xtn
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Until you can actually prove damage is going to occur from coolant entering at a slightly lower temp, this is a moot point.