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Glutton For Punishment
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251 Posts
Discussion Starter · #1 ·
My A/C knob on my 88 esprit just spins and spins. I am assuming that it is bad, but just want to check, should it click in the off position and have a stop at full on? I have verified that the knob is correctly attached to the rheostat. I have not tested the connections on it to know what it is doing electronically.

It is starting to get hot here, and its time to fix the A/C

Thanks
 

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Cal H
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982 Posts
Why yes, it should do that. That is how it works on my old 90 and my present 91. The controls look the same as yours. Starting to get hot? We just got a foot of snow again. Bah Humbug
 

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Super Moderator
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4,218 Posts
My A/C knob on my 88 esprit just spins and spins. I am assuming that it is bad, but just want to check, should it click in the off position and have a stop at full on? [snip]
Thanks
Yes - It should turn about 330 degrees and click on CLOCKWISE (OFF).

Note that the KNOB has some spring-loaded pin that 'locks' onto the spindle.

Is it possible your knob's pin is stuck; causing it to stay on the spindle, but not allowing you to ACTUALLY turn on the A/C?

Use a paper clip to push on the pin to make sure it's actually locked on.
 

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Wingless Wonder
1988 Esprit Turbo
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6,359 Posts
That knob (if connected per Eddie's instruction) is connected to a capillary-tube control. (Not a rheostat) Anybody remember those?
 

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Glutton For Punishment
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251 Posts
Discussion Starter · #5 ·
Hmm I guess this will require some further investigation, much like everything else on this car. I had the radio out and took a cursory look, but it was the middle of winter and not high on the list at that time. The rest of my knobs don't really line up with the printing on the panel, so I guess I get to take it all apart, adjust my cables, and figure out this "capillary tube" device.

In my early years, windows down and top off would suffice, but that was many years ago.
 

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Wingless Wonder
1988 Esprit Turbo
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6,359 Posts
If you look at this Vintage Air article from Popular Science (circa 1969) you will see what I'm talking about...Look on "page 125" at the "Thermostatic Tube in Cooling Coil" --- that's what the Esprit's system uses.


http://tinyurl.com/kdzeqr6

Am I older than dirt, or what?
 

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Super Moderator
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4,218 Posts
Sounds like you don't have the 88 driver's handbook? I have scanned a few pages - here's the interior climate control instructions. Note the knob stops on left and right (from hot to cold) - definitely should not spin around. See last paragraph on right page.

The knob can be positioned/realigned, but I find it a little harder than it looks.



Here's the semi-disassembled view - note the lockscrew (green circle). If the entire assembly is spinning, you want to make sure that screw is still there.

 

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Wingless Wonder
1988 Esprit Turbo
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6,359 Posts
Eddie,

The green circle you pictured is on the heater control.

I thought ExtraTX was talking about the A/C control knob to the upper right of the panel. (The one labelled TEMP and AIR CONDITIONING in your owners manual scan)

Does that have a locking screw also? I've never had the controls apart.
 

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Registered
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175 Posts
All of these knobs are held tight by various means. the two large knobs "click" into place. The two smaller ones have a 10mm nut that has to be tightened to hold them into place. Not too tight, but not too loose either...

The two smaller knobs also have set nuts behind the actual knob. Same idea... they must be tightened enough to keep the assembly from rotating 360.


Cameron
 

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Super Moderator
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4,218 Posts
Ah, I screwed up - yes - Atwell and Cameron are correct. I fixated on the temperature switch because that's the one that isn't working quite right on mine.:facepalm

Yes - the AC switch at the top uses a regular hex nut to hold the assembly. :rolleyes: and does have some type of position stops.

Note the weird ducting switch - 'Normal' is not that normal to me. You have to play around with it (or read the manual, which I eventually did). The manual is written with a straight face about how it 'works'.
 

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Glutton For Punishment
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251 Posts
Discussion Starter · #11 ·
Yes I am talking about the ac knob not the heater control. I have that one figured out, but it needs to be realigned as it doesn't point at the correct color.

My ac knob just spins. I have verified it is tight via the nut. Wil be disassembling it soon. Thanks for the scan. I need to read the part about the vent control knob. I haven't figured out the language on that one yet.
 

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Super Moderator
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4,218 Posts
[snip[
My ac knob just spins. I have verified it is tight via the nut. Wil be disassembling it soon. Thanks for the scan. I need to read the part about the vent control knob. I haven't figured out the language on that one yet.
Sorry - posted the wrong picture - this is the one that describes the AC knob settings:

 

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Glutton For Punishment
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251 Posts
Discussion Starter · #13 ·
Turns out the a/c is controlled by a potentiometer and control unit (ACU) also known as an amplifier in some circles. The potentiometer has an off switch built in.

So it switches two wires for on and off ( black and blue) and has a resistance value between the two other wires. It is a max of 85K ohms (printed on the side) and down to 0 ohms at full cold. There is also a thermistor on the evaporator that feeds a resistance back to the ACU so the ACU knows how cold it really is.

Mine is busted, and one from lotus is over $100. From radioshack these are $5.99 but 85k ohms is not a normal resistance. Pretty sure close will work, just need to get the diameter of the shaft right.

Interestingly the potentiometer has the first two of the three posts bridged which doesn't make sense to me. Posts 1 to 3 are supposed to always measure 85k ohms when measured between the two, and post 2 is the wiper that varies with the knob.

I'll post a source if I can track down a good replacement.
 

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Integrator
Joined
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2,963 Posts
X180 R12 Air Conditioning

If you look at this Vintage Air article from Popular Science (circa 1969) you will see what I'm talking about...Look on "page 125" at the "Thermostatic Tube in Cooling Coil" --- that's what the Esprit's system uses.


http://tinyurl.com/kdzeqr6

Am I older than dirt, or what?
Atwell,
That is a fantastic article!

Please post more info, if you have any links.
I want to keep my cars R12. I bought original R12 on eBay-plenty there.

My intention is to collect all the A/C expertise into a one thread.

Please chime in-anybody, R12 ONLY.

Look here: http://www.lotustalk.com/forums/f164/rebuild-my-c-my-s3-turbo-192914/

http://www.lotustalk.com/forums/f164/air-conditioning-system-x-refference-parts-list-116908/
.
.
 

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Registered
1986 Lotus Esprit HCI
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98 Posts
Thread type?

All of these knobs are held tight by various means. the two large knobs "click" into place. The two smaller ones have a 10mm nut that has to be tightened to hold them into place. Not too tight, but not too loose either...

The two smaller knobs also have set nuts behind the actual knob. Same idea... they must be tightened enough to keep the assembly from rotating 360.


Cameron
The two knobs are held on by a nut which screws on to a ferrule which holds the knob to the shaft of the rheostat. Does anyone know what thread these nuts are?, Having a tough time finding a replacement, as they don't appear to be SAE, or metric.
Thanks
Jeff
 
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