Ready to retrofit air-con

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AndyLotus
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Ready to retrofit air-con

Post by AndyLotus »

Well after a few months of collecting bits for my air con conversion I'm almost ready to make a start.

I shall do my best to take photos as I go along in case anyone else has the same mad idea.
So far I've spent £350 on the parts with about another £100 to go for all the hoses and a drier.

A couple of questions about the standard Excel air con if I may....

1) Do the fans come on all the time once you have pressed the a/c switch? (Even when moving at speed)
2) If you want to help clear the windows on a cold day I assume the a/c is switched on, but you move the slider to hot so in effect the air coming out is chilled and 'dried' then re-heated by the heater matrix? I don't think the compressor has a thermostat built in from what I can see.

Many thanks and wish me luck. :D

Simpatico
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Re: Ready to retrofit air-con

Post by Simpatico »

Certainly on other cars the answers to both questions is yes, but an expert will confirm that shortly.

Best of British, a worthy project (I love aircon) 8)
I am an EX owner; I have ceased to be

Pjr
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Re: Ready to retrofit air-con

Post by Pjr »

Andylotus,

I do wish you luck! It would be great if you could tell us which parts you got, from where and the individual cost. I have non-functioning a/c and I have been putting off doing anything about it. If you have found any generic substitutions then we'd love to hear.

The PO told me that the main radiator is shot, but I haven't dared look!

Unfortunately, I can't answer your questions, but good luck anyway.

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amarshall
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Re: Ready to retrofit air-con

Post by amarshall »

1) only when the compressor clutch is engaged - which is related to engine speed - and only the fan nearest the condenser.
2) yes - but it isn't reheated much.
https://www.lotusexcel.co.uk/
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AndyLotus
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Re: Ready to retrofit air-con

Post by AndyLotus »

Thanks all, I'll try and keep track of all the bits and cost. I shall also try to make sure I take some photos.

Angus: Thanks for that. What exactly do you mean by 'related to engine speed'? I was under the impression that as long as the switch was pressed the clutch was engaged, assuming no leaks, pressure incorrect etc.
I'm trying to decide whether to use all the existing control components or allow the trinary switch, I shall fit, to control the fans. In theory if forward speed is sufficient then I shouldn't need the fans to be on all the time, only at slow speed or stationary.

I hoped point 2 was the case, it helps to keep things simpler without needing a separate stat for the evaporator temperature.

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amarshall
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Re: Ready to retrofit air-con

Post by amarshall »

AndyLotus wrote:Thanks all, I'll try and keep track of all the bits and cost. I shall also try to make sure I take some photos.

Angus: Thanks for that. What exactly do you mean by 'related to engine speed'? I was under the impression that as long as the switch was pressed the clutch was engaged, assuming no leaks, pressure incorrect etc.
I'm trying to decide whether to use all the existing control components or allow the trinary switch, I shall fit, to control the fans. In theory if forward speed is sufficient then I shouldn't need the fans to be on all the time, only at slow speed or stationary.

I hoped point 2 was the case, it helps to keep things simpler without needing a separate stat for the evaporator temperature.
Working a bit from memory, but ISTR that the clutch doesn't engage until engine speed is over 1000 rpm - and the throttle jack is there to keep it at that when aircon is on full auto mode on SEs. On base & SA it should drop out at 700rpm and not re-engage until 1000rpm.
(this is all based on a normal idle being 950rpm according to service notes) It also disengages if the frost protection sensor kicks in or if there is low pressure in the system to protect the compressor.

Then there's eco mode where it cycles on and off, providing less cooling but saving a bit of fuel. I think the system uses the same principle as the frost protection, but set at a higher temperature and also seems to have higher rev limits for drop in and out, but that could be my imagination.
https://www.lotusexcel.co.uk/
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AndyLotus
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Re: Ready to retrofit air-con

Post by AndyLotus »

Right ok thanks. As I don't have a throttle jack it looks like I shall have to get a little imaginative.

The idle speed should be controlled by the mapped ignition I'm fitting. If the load from the compressor drops the idle speed, then ecu advances the timing slightly to pick it back up again. I'm hoping it will give me a nice stable idle.

Perhaps it will be better if I use the trinary switch to do the cutting in and out dependant on the pressure and also operate the cooling fans.

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Re: Ready to retrofit air-con

Post by amarshall »

I think the low pressure disengage is built in to the compressor.
https://www.lotusexcel.co.uk/
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AndyLotus
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Re: Ready to retrofit air-con

Post by AndyLotus »

I think the low pressure disengage is a sensor mounted on the evaporator pipes, inside the car. At least that what it looks like on the unit I have.

I was going to use the trinary switch in place of this switch as it only senses low pressure not high pressure. The trinary should sense both cases. At least that's what I'm hoping :lol:

To be honest I have a different compressor and a different condenser so we shall see, I like a challenge.....

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Re: Ready to retrofit air-con

Post by andy brad »

The excel system is very simple when you switch it on both fans run and comp clutch will engage there are no pressure switches in the system so it will run regardless of engine speed and gas charge you should never run the ac comp without gas charge as it relies on the cold gas and oil in the suction pipe to cool and lubricate the compressor. if you have no gas charge pull the wire off your compressor so at least you get a back up of cooling fans if the fan stat fails by switching on the ac.
Had my celebration from new still have it its done 90 od thousand miles and i have been fixing car ac for thirty years.
andy b

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amarshall
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Re: Ready to retrofit air-con

Post by amarshall »

andy brad wrote:The excel system is very simple when you switch it on both fans run and comp clutch will engage there are no pressure switches in the system so it will run regardless of engine speed and gas charge you should never run the ac comp without gas charge as it relies on the cold gas and oil in the suction pipe to cool and lubricate the compressor. if you have no gas charge pull the wire off your compressor so at least you get a back up of cooling fans if the fan stat fails by switching on the ac.
Had my celebration from new still have it its done 90 od thousand miles and i have been fixing car ac for thirty years.
andy b
Sorry, but wrong. If your system behaves like that, it's faulty or not as it left the factory. There is a pressure switch to protect the compressor and only one fan should run.
https://www.lotusexcel.co.uk/
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robertverhey
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Re: Ready to retrofit air-con

Post by robertverhey »

Yep, low pressure switch is standard fitment, as per the original toyota ma61 gear from which this system sourced
Robert Glacier Blue '87 SE

andy brad
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Re: Ready to retrofit air-con

Post by andy brad »

sorry boys as i said i have had the car from new i know it inside out could be cars for export were different but mine is as it left the factory i was a fridge engineer all my working life
every day is a learning day
andy b

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Re: Ready to retrofit air-con

Post by robertverhey »

"Low pressure cut-out switch" Shown and described on pages 11 and 12 of section PC of the factory service notes. From memory accessible via removable panel at rear of glove box.....or by reaching up behind heater unit in passenger footwell, can't recall how i got to it. But it's there.
Robert Glacier Blue '87 SE

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amarshall
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Re: Ready to retrofit air-con

Post by amarshall »

Mine is UK spec and definitely has a low pressure switch.

I haven't seen one of the later cars without one.

If you don't have a low pressure cut-out your car is not to spec.
https://www.lotusexcel.co.uk/
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