2007 Exige AC/heater rework - LotusTalk - The Lotus Cars Community
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post #1 of 40 (permalink) Old 01-29-2016, 10:27 AM Thread Starter
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2007 Exige AC/heater rework

So, the fan didn't work when I bought it, known issue, clam is off and going to be doing the resistor repair, in addition the heater bypass and AC improvements/insulation, and thermostat update

A few questions/comments;

Anytime you read too much, there are conflicts on advice. for instance, in the bypass thread, there is the suggestion to enlarge the air intakes, while in the ac improvements thread it is suggested to close them off. Those enlarging report better airflow. Those blocking off report colder AC

Examining the heater box, I realize that the fan is set up so that one side takes only outside air, the other only inside. It occurs to me that if one were to block the exterior side of the fan while the heater box is out, one could leave the vents open, and allow them to dump into the heater box area, ventilating it and perhaps cooling that area down, eliminating the need for the small vent hoses added in the heater bypass thread. Testing the fan on the bench is is obvious that with one side blocked, the flow is diminished. So if one determined that outside air was not wanted, it might make sense to build a little duct from the recirc plenum over to the other side of the fan to increase the air flow.

I think as part of the AC improvements I will clean the recirc plenum pieces and tape them up with aluminum tape[the best stickiest tape for ducts, as opposed to duct tape]

I read that the recirc flap is a POS, has anyone ever tried to improve that? Seems to me that would fix a few ills. Is it possible to get it out when the heater is out? not obvious at a glance

It also seems to me that the entire heater box area should have been sealed up which again would have made the system operate better. Not to mention keep water out which would have saved the heater resistors.

It also does not look like the recirc plenum holes line up very well with the fan, that doesn't help airflow


Anyway those are my thoughts as I dive into this....
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post #2 of 40 (permalink) Old 01-29-2016, 10:45 AM Thread Starter
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So figured the recirc control removal[as usual the parts manual is more use than the service manual]


Looks to me like keeping that control door oiled and putting some sealing surface on it would make that pretty airtight

Would also think the excess air flap would lat a fair but of cold air into that area
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post #3 of 40 (permalink) Old 01-31-2016, 11:04 AM Thread Starter
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I tested the 100 watt resistors outside of the heater box today. It became obvious pretty quickly that a heatsink is required, and with one bolted on the medium resistor topped out at 190 some degrees. No hotter than the heater hoses etc in the area. Plenty of heat when it is in the plenum and you are trying to make cold air. Low speed ran the resistors perhaps a bit cooler.

It is little wonder the stock setup failed. even with the fan blowing over the case, they must have been very hot, over boiling no doubt helping cause the connection failure
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post #4 of 40 (permalink) Old 02-02-2016, 08:45 AM Thread Starter
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So my looking everything over and thinking about any things that might be useful to do that are not mentioned in previous threads I have come to this:

I am going to leave the external air open. Basically when you look at the shop manual pics, the system should work, but as with many things Lotus, the execution leaves much to be desired. In the pic below, the 'recirc' door has no edge seal, and the entire fresh air panel has no sealing and is just stuffed in the hole with a single bolted clip holding it in. I have added sealing foam to the door. I plan on sealing the entire fresh air panel with aluminum tape to ensure that when you want recirc, you get it, not extra air from where you don't want it.
In addition to insulating the recirc plenum I plan on sealing it as well, as while it has some attempt at sealing[foam on the edges] it does not pretend to fit in the space allotted, and thus hot air from the heater box area leaks in. I am trying to think of a way to make sure the rubber flap stays closed and does not let hot air into the heater system, but continues to let air from the nose into the heater box area hopefully cooling it.
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post #5 of 40 (permalink) Old 02-03-2016, 10:18 AM Thread Starter
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So I just received this heater valve:



An Old Air Products 50-1555 electronic valve. If figured worst case I would have to get some help creating a conversion circuit to run it from the stock temp pot. Well it runs from 0-12 volts open to close and so does the temp door actuator, so in theory I can just splice it in in tandem with the temp door and have both of them run at the same time.

link says robot check, thats funny

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post #6 of 40 (permalink) Old 02-03-2016, 10:37 AM
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Wow, I am going to revisit this when I have more time later. A quick summary of my upcoming projects: fix the heater bypass mod on my car, find out why diverter flap doesn't go through full range of motion, check on resistor pack, see why my blower speed knob caught itself on fire. Seems like we may be able to help each other out a bit! Haha


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post #7 of 40 (permalink) Old 02-03-2016, 11:21 AM Thread Starter
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I am willing to bet the blower speed know happened because while we call it the resistor problem, it is really the connectors that die. I bet your connector rotted off and then the wire touched ground, poof
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post #8 of 40 (permalink) Old 02-03-2016, 11:48 AM
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Quote:
Originally Posted by exigegus View Post
I am willing to bet the blower speed know happened because while we call it the resistor problem, it is really the connectors that die. I bet your connector rotted off and then the wire touched ground, poof

That's where it gets more interesting though. It caught fire in the rain several years ago and has since worked fine, even in rain. That knob carries all the blower current (not something I'd think you want to do..), so I think some salt water got on the resistor pack just enough to draw more current through, the knob warmed up, and some lint/insulator was the first to tap out from the heat


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post #9 of 40 (permalink) Old 02-03-2016, 12:53 PM Thread Starter
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I tell you the more I look at this the more it looks like the heater was designed to be under a cover. The blower motor, ac connections, heater hoses, thermostat control, and the part where the output hose flares out, all sit under about 8 1/2 inches, there are 6mm threaded inserts at 9 1/4 on the front cross beam and rear cross beam[chassis sections that define the heater area] so it would be pretty easy to make a plate that covers that area and insulate it. This would prevent hot radiator air from entering the heater area, and allow you to delete the front blower seal and, I think, greatly increase the airflow through the blower. This is predicated on the fresh air duct being actually airtight, and I think the upper suspension mounting points will have to have a better closing plate than a piece of foam stuffed in. The heater box cover would have to be sealed at the edges and the perforations for the heater hoses, ac lines, ground wires, hvac duct, and ac thermostat.

Attached are pics of my final version of the fresh air door, and a bar showing the top line of the heater box, where I could have a plate running about a half inch above it. I enlarged the openings for both the fresh air to the blower and the fresh air bypass flap. while I added foam to the edge, it will be taped in place for air sealing. If I do the heater cover I will have to either block the bypass flap or make a way for it to spill into the area above the heater cover.
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post #10 of 40 (permalink) Old 02-07-2016, 12:35 PM Thread Starter
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I removed the recirc blanking plates the other day, and my first thought was, 'there is no way that is enough area for the fan'

So I did some math. turns out the 156 holes at about .38 inches diameter, amount to about 17.7 square inches of area, and the one side of the fan that draws from them has a gross area of about 15 square inches then subtract the supports it is more like 13, so what that tells me is that someone did the math originally[and that guy is probably pissed that the system came out so poorly]

I decided that what would solve the ills of the ac is a cover the heater area, insulated and taped airtight
Attached is a pic of the mockup in .025 aluminum, I have slightly heavier [1/32] mat'l coming monday


The idea is to move the heater box area into the cockpit, like um, every other car in the world. Once that is done, and the fresh air duct is actually sealed, I could remove the seals around the fan, allowing both sides of the fan to draw equally, increasing airflow especially when the fresh air is closed.

Maybe then it will need more holes......

More math, that may or may not actually make sense, as I am not an HVAC engineer.

The output of the blower is 14 some square inches. The 3.5 square inch [corrugated] output hose is 9.6 square inches, an obvious restriction, 4 inch seems doable and would be 12.5 square inches

So, funny thing, what happens when you air flow restrict an AC evaporator, and feed it humid air....it ices up
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post #11 of 40 (permalink) Old 02-07-2016, 12:41 PM Thread Starter
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I am ruminating on whether I can keep the flapper feeding fresh air into the area above the cover. If you look at the area around the AC tube in the pic of the heater box, I think I can block it off from the newly isolated heater box area and direct it up through the cover to keep the area above cooler, since the ac system will no doubt draw some air through gaps. I worry that without the flapper the air pressure might defeat the seals of the fresh air door.
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post #12 of 40 (permalink) Old 02-16-2016, 04:34 PM Thread Starter
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So tomorrow I should have time to make a finished box cover.

Meanwhile, I have finished the recirc plenum. I am kind of doing things that won't be necessary for me when I am finished to show what I think should be done, so I have added insulation to the recirc plenum. even though in my finished application it isn't required

So in the pics, I have edged the plenum pieces with foam, and added a strip of foam to the chassis. Both places I cleaned with acetone first. The acetone softens the ABS a tiny bit[be judicious] to really bond the foam tape. The aluminum tape should seal it tight if the foam leaks. You can see the extra opening I added for more recirc airflow, this works with my planned added cover, but I would not even think about doing it with an open heater area, it would just let more hot air in. I place it where I did so I should be able to cover it up if my scheme dose not work for some reason.
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Last edited by exigegus; 02-16-2016 at 05:50 PM.
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post #13 of 40 (permalink) Old 02-16-2016, 04:53 PM Thread Starter
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So I bought an old air products valve model 50-1555.




It is servo actuated, so I figured worst case I would steal the circuit posted on this site
https://www.lotustalk.com/forums/f313...ass-mod-79637/
, and run it with a switch or integrated pot. Best case it would run on the same voltage as the Lotus one and I could wire it with no additional wires

Well, guess what, it runs on 0-12 and will run in tandem with the heater door actuator in the heater box.

No added switch, no wires to the dash.

I found the connectors that Lotus uses for the heater control, and made a harness for it. While somewhat pricier than the cheapest available, it integrates seamlessly. i am thinking it will change the heater curve a bit but who knows if that is good or bad, most would never notice.

I can post a wiring diagram, but you can actually see it in the pic. Only trick is they use brown as 12 volt power and red as control where you might expect the reverse. The valve has power, ground and control line to what was a pot[which is discarded] and a separate power and ground source. Since we can get power and ground from the Lotus harness, why not, some nerves at first in case I smoked something, but no worries testing on the battery, works in the car

TE connectivity part numbers for the 3 pin housings:

1-174928-1

174921-1

pins
173645-3
173630-6

They are a standard F crimp, I used a crimper I bought for Lucas terminals[not the commercial insulated type] and as I found out from doing this type of thing years ago, as long as the F crimp crimper is for the right gauge, a little care and they crimp fine. The totally correct crimper makes it mindless with your eyes closed job, this way you have to pay attention
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post #14 of 40 (permalink) Old 02-16-2016, 05:01 PM Thread Starter
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Pic of the fresh air door taped into the car for air sealing

put a shop vac output to the front vents and there is some leakage around the servo motor but otherwise tight
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post #15 of 40 (permalink) Old 02-16-2016, 05:10 PM Thread Starter
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I don't know if it is just me, but my heater box had quite a bit of sand in it, no doubt from the nose vents. I am going to add a bit of filter material to the fresh air side to stop that.
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post #16 of 40 (permalink) Old 02-20-2016, 01:08 PM Thread Starter
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To try and get the air flow maximized I looked for some smooth bore tube. Turns out the silicone tubing on ebay is the cheapest solution.
89mm 3 5 " 45 Degree Elbow Silicone Hose Turbo Intake Intercooler Pipe Black | eBay

a pair of 45 degree angles cut down and fit in place will do the trick
https://www.lotustalk.com/forums/atta...hmentid=668825
when I am all done it will get insulated

my final heater area cover ahttps://www.lotustalk.com/forums/attachment.php?attachmentid=668833ll cnc cut to size

it will also get insulated and taped air tight when complete
I split into 2 pieces as it is impossible to get it in there without bending it. If the brake lines had been dressed properly it would not be a problem

looking for places to attach my heater valve and fan resistors
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post #17 of 40 (permalink) Old 02-20-2016, 01:39 PM Thread Starter
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I am going to attempt to see if I can see the air flow differences between both sides of the fan being used and one side[as stock] and maybe the smooth vs corrugated hose.

I still think a 4 inch hose would make a difference. It does seem that the hose is the biggest restriction in the system.

Oh, and the Lotus resistor kit, at least as pictured in the parts manual, blocks off a bunch of the recirc side of the fan, what a terrible idea in a flow limited system
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post #18 of 40 (permalink) Old 02-22-2016, 08:19 AM
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This is going to be the best hvac system in any elise/exige!
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post #19 of 40 (permalink) Old 02-22-2016, 03:34 PM
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Can't wait to see the final results.
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post #20 of 40 (permalink) Old 02-23-2016, 08:08 AM Thread Starter
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Well, the hope is that if I can make it work decently then anyone can. It sure looks like the heater/ac should be capable of dong the job, it is just not installed with any attention to detail


Amazon had cheap air flow meters so I picked one up 25 bucks. I am not concerned with absolute accuracy, just repeatability.

Measuring airflow at the face level vents, the right most vent has much higher flow than the others. Adding the numbers up and doing the FPM x area math with an online calc, it looks like with both sides of the fan open, about 77cfm is coming out those vents. The output of the heater box seems to be about 200 CFM

So a lot of air is wasted in the heater diverter area inside the car.




I thought about it last night and ran various things through my mind, how can I control the heater flap independent of the vent/defrost diverter..........
I decided I would try simply disconnecting and propping open the heater flap to see how badly the airflow is out the vents with the flap wide open. I popped the lever off of the footwell flap[warning it trashed the clip, probably costs 50 cents] and taped it wide open, wider i think than control allows.


The flow out the face vents dropped a whopping.......3 cfm

A rough measure of the airflow coming out of the foot vents is about 11 CFM, and it sure seems like that airflow is reading low, but it is both hard to measure the size of those odd shaped vents and get the meter where I can read it and it is in the airflow

10 percent more AC capacity anyone?

The defrosters seem to blow plenty strong with the heater door propped open, which was what I was truly afraid of.

The sole downside I can think of is the passengers feet will get cold, causing I would think, for the first time in history a person in an Elise/Exige asking to turn the AC down .......

Damn I hate that it is cold about everywhere this time of year

If anyone wants to try this, this is how you remove the heater door actuator:

Remove access panels to expose the top of the heater air hose where it enters the car, remove the hose so you can see what you are doing.

To the right of the duct entry[as you are standing in front of the car looking at it, left side in standard car parlance] you will see the small rod coming forward and attaching to a small plastic lever attached to the heater door[which you can see inside the duct opening as a steel bar passing across the bottom] I used two small screwdrivers to pry the plastic lever away from the flat end of the metal rod, and as soon as there was a little space I used them to work between the metal end and the clip , since I was nervous of breaking the plastic arm. Eventually the clip broke, they should be a hardware store part.


[edit]

A bit of gorilla tape should hold it open for the time being. the rod seems to harmlessly move around when detached, may need something to stop it rattling when actually driving
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