AC Switch Replacement

[Jason Rushing]

I purchased some pretty aluminum switch knobs from PNM to replace my cheap plastic switches for the entire AC panel, 4 of them in all. All was going well until I attempted to remove the far right AC switch knob. Well, when I say going well I realized the set screw was tapped on the opposite side of the flat spot on the OEM switches, so I did decide to drill and tap a new set screw hole on the side of the new switch knob that faced the flat side of the actual switch.

 

When I tried to remove the AC switch knob I had to use quite a bit of force to pull it off and when it decide to come off the potentionmeter and ON/OFF switch for the AC compressor decided to self destruct. 

 

The AC Switch potentionmeter/adjustable resistor/rheostat, whatever you want to call it is no longer supported by Lotus, as if that comes as any surprise to any Esprit owner. 

 

SJS does have an AC Switch but they want $80.51 and looking at their picture it requires some slight modification to install. 

 

The stock OEM AC switch is actually soldered in and does not have a plug type connector, the SJS has a plug type connector and appears to come with the necessary plugs to adapt it to the car.

 

So the potentionmeter is marked with B5K Ohm and has an integrated ON/Off or SPST switch. 

 

I found this potentionmeter on Ebay for the high price of $1.44, yes that is less than $2 US each, so I purchased 3 at $1.37 each plus shipping. I got 3 in for less than $10 US.

 

The first thing is that you will notice the  physical size of the ones from Ebay are almost twice as big as the OEM  switch, though it does fit in the OEM hole with one minor adjustment needed.

 

I used a 9/64 drill bit to drill a new hole for the little set stud to fit in to keep it from rotating. The other noticeable difference is the switch stud for mounting the knob. 

 

Due to the larger size once I had the new AC Switch soldered in I wrapped it with some electrical tape to avoid any potential contact, and shorts, with the mounting frame.

 

I started the car and the new switch worked as new. 

 

I have no idea why the Lotus engineers designed the car with an AC computer that doesn't just turn the AC compressor clutch on with a simple ON/OFF signal like every other car on the planet. Since the AC clutch only turns on at full 5K resistance on the potentionmeter, (what the heck is the use of the potentionmeter???), I don't see why we couldn't just wire in a 5K ohm resistor in the circuit, remove the potentiometer, and just use a good old fashioned ON/OFF switch like every other car on the planet...

 

In the end, if you are not afraid to use a soldering iron and a drill, you can replace the AC switch for less than $10 US if you ever have the need. I have no idea how to source the smaller OEM, possibly micro potenionmeter, but these slightly larger ones that do the trick and can be had cheap.

[ramjet]

Well done.

[ab2cv]

Ha, it seems like we did the opposite thing - could've just swapped knobs! 😄 Also interesting that the cigarette lighter is on the opposite side - guessing Lotus swapped this round for left hand drive cars?

 

[Jason Rushing]

I don't follow, what did we do opposite and what do you mean swapped the knobs?

Did you unscrew the switches and rotate them 180 degrees so that the flat spot on the switch matched up with the location of the set screw on the new knobs?

I just though about that as a solution instead of drilling and tapping a new hole on the opposite side of the knob for the set screw.

[ab2cv]

16 hours ago, Jason Rushing said:

I purchased some pretty aluminum switch knobs from PNM to replace my cheap plastic switches for the entire AC panel, 4 of them in all.

I purchased some reproduction (not so cheap) plastic switches to replace my aluminium knobs that a previous owner had fitted.

[LotuStuart]

>I have no idea why the Lotus engineers designed the car with an AC computer that doesn't just turn the AC compressor clutch on with a simple ON/OFF signal like every other car on the planet. Since the AC clutch only turns on at full 5K resistance on the potentionmeter, (what the heck is the use of the potentionmeter???), I don't see why we couldn't just wire in a 5K ohm resistor in the circuit, remove the potentiometer, and just use a good old fashioned ON/OFF switch like every other car on the planet...

 

Does it? I'm pretty sure mine (2002 V8) acts as I'd expect it to-if I turn it to max it comes on whatever the inside temperature is, but if I turn it to only just on or half way, then the AC cycles as it reaches that temperature. Mind you, I haven't had it on "in anger" this year.

Maybe your cabin thermo switch has been bypassed, or is broken/shorted?

 

[LotuStuart]

On 27/04/2023 at 04:18, Jason Rushing said:

When I tried to remove the AC switch knob I had to use quite a bit of force to pull it off and when it decide to come off the potentionmeter and ON/OFF switch for the AC compressor decided to self destruct. 

Did it have grub screw holding it on?

[Jason Rushing]

No the plastic switches are a friction fit, they just push onto the stem.