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Been fighting the heat issue. On any day, the interior vents were nowhere near ambient temperature. The only two ways the car was comfortable was to either run the AC or turn the heater to the Defroster and keep the top off. Did some playing today and here is what I found.

1. My heater flap never closed fully. I would cycle the flap through and it never closed that last 1/4 inch. This always let heat in the system, and I am pretty sure that the flap vs heat ration is non-linear. Lots of heat with little opening, not that much more heat with lots of flap opening. From the experimenting I did, the temperature control knob only controls the position of the flaps. Didn't check with the AC button pushed, but I suspect the same is true.

2. thermocouple that should be touching the A/C condenser, to prevent icing, was about 1/2inch off the condenser! This may have been caused by the fact that there was nothing securing the thermocouple to the mounting bracket.

Here is what I did.

Added the heater by-pass. This doesn't fix the heater flap issue, but at least the heater core is not hot now. Did a quick test drive and now there is no temperature change at the vents if you adjust the temperature knob from full counter clock wise to full clock wise! This is good.

Zip tied the thermocouple to the mounting bracket, and adjusted to touch the A/C. This can only help.

I was looking at adding the vent tubes modification to vent air near the master-cylinder and made a big discovery. Either my my car is missing something our we all are missing something!

I was trying to think aerodynamics and see where the best place to get cool air into this area was and then I noticed it. The problem is not getting the cool air into this area, its keeping the hot air out. Normal workings are: The air comes in the grill of the car, up through the radiator, and then most of the air goes out the vents on the top of the clam. BUT a bunch of the hot air follows up the central spine of the clam, the painted part that is directly below the windshield wiper that divides the two grills, past all the heat shields, and dumps into the area above the heater box & the foot box. Didn't add the 2 1 1/4inch tubes to try to counter act the 6+ inches of hot air being injected in the same area. To see what I am talking about, take off one of the front access panels and follow from the wiper to the radiator via the center spine.

Am I missing a heat shield that goes directly underneath the center spine? I looked up the parts manual and found the left and right heat deflector, (46.01, 19 & 20), but no center deflector. Is my car missing this?

As a test i am using some masking tape to block this area off and taking the car out for a spin.
 

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Did about 20 miles of "testing" and here is what I found. Out side temp, as per local TV station 88 deg. Engine temp as per dashboard 194.

Before "Testing" After Testing
Dash Temp "R" in airbag pass side 102.1 109.6
Dash Vent Output Temp By-Pass on 110.3 112.2
Dash Vent Output Temp By-pass off 110.3 145.7

Thanks Tony. Now I am going to fabricate a heat deflector for the center spine.
 

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Michael,

I agree. Its just that I found, on my car anyway, a BIG place where the hot radiator air can heat soak the top of the heater box and the fount of the peddle box.

There was a 4 1/2 by 6 inch hole for the hot air from the radiator to blow directly on the big hose that connects the heater box to the dash board.

Doug
 

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Doug,
I guess the answer is to try to insulate the duct and take before and after temperature testing under similar condition.
Michael
Michael,

I agree. Its just that I found, on my car anyway, a BIG place where the hot radiator air can heat soak the top of the heater box and the fount of the peddle box.

There was a 4 1/2 by 6 inch hole for the hot air from the radiator to blow directly on the big hose that connects the heater box to the dash board.

Doug
 

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BUT a bunch of the hot air follows up the central spine of the clam...
Mine has a block of foam glued into the underside of the spline. It came from the factory this way. You can see it in this picture:

 

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dang, there goes my aftermarket get rich scheme. That black piece is exactly what my car did not have, and I fabricated today. On the dinner run with the lovely bride, the car was pleasant to be in, not the mobile sauna I have come to know.
 

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Still a good discovery. I plan to check mine tomorrow.

I had to undo Viper's mod to open the footwell vents, due to excessive radiator smell coming in from said vents. bet my 2005 does not have the blocker.
 

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good catch...I will check mine..
 

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Well, the good news is I have the foam...bad news is that it is oriented straight vertical (up and down) and so does not provide an effective barrier. It also may be a bit small, but I will attempt to re-orient it. Seems to be glued in.
 

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the one I made:

The bottom of the deflector was touching the radiator
The left and right side actually overlapped the two heat deflectors directly under the access pannel
The top had a tong that I taped up to the bottom of the central spine on the clam. I can take a picture tonight if ya want.
 

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There are some pics of my solution.

The top pict is the foam piece as I cut it out. I uses some GM under hood sound insulation that is about 3/4 of an inch thick.

The three fingers go to the top of the install. The thick middle finger is taped to the underside of center spine. The two smaller fingers go on either side of the spine, just above the rain gutters (dont block the gutters). The bottom tucks in behind the back of the radiator

The next pictures just show the piece installed. I circled the foam piece, just because.
 

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Nice work Doug! I have the foam block but it is about three inches aft of the radiator allowing about 9 cu" of hot air to flow straight on to the AC hose, cant believe I overlooked such an obvious hole. I had about the same results as you with the by-pass.... major improvement, the elec. thermostat solved freeze up issues and opening up the drivers side floor vent increased air flow some. Driving the TX. hill country this weekend, it will be a good test.... hope this may be the final solution.
 

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Nice find Doug. I have the center spline insulation block, but as 407Driver said there is a large gap in the bottom of it to allow hot air through. I am going to use the same insulation that I used to insulate my side sills to cover that opening. Do you mind if I add this to my http://www.lotustalk.com/forums/f92/improved-c-heating-system-71031/ and credit you with the find :bow:
Michael
 

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You bet you can add it. Glad I could give back something.
Score now Doug 1 LotusTalk 999,223
 

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Doug,
Done, thanks. After I insulate I will take vent temperature readings to compare to "before" readings and post the results. I know that after driving for 10 miles approx. the vent temps. increase about 8' which I know are cooling system heat soak related.
Michael
You bet you can add it. Glad I could give back something.
Score now Doug 1 LotusTalk 999,223
 

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Interesting I just started noticing this evening the car felt awfully hot even with the top off despite it being only about 70 out. No matter what way I moved the vents I felt hot air. I gotta do something like add the foam.
 
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