- Feb 5, 2024
- 181
- 325
- Funster No
- 101,061
- MH
- Etrusco CV540 DB
My Etrusco conversion on a Fiat Ducato van has only basic manual aircon in the cab. Although described in the manual as climate control, it is no such thing, as the aircon has to be manually switched on and off with a button above the heating controls. Although the base vehicle does have the option of a proper full climate control system this option was not offered by Etrusco. On a recent trip we found that we were alternately hot and cold due to not operating the manual control in a timely enough manner to maintain a steady temperature. This set me thinking about whether it would be possible to automate this. I had already added a light sensor driven circuit to automatically turn on the headlights in dark conditions and although it was difficult to get at the wiring for the lighting stalk, once I did I found that in the ON position the switch simply connected one wire to ground to turn the lights on so a relay connected in parallel could do the same, driven by the light sensor module.
The AC control turned out to be a bit different in that the switch was not a latching one as in the headlight stalk, but a momentary one, meaning that it does not stay in an an ON or OFF position, but instead one press of the switch turns the AC on and pressing it again turns it off. It is not possible to emulate this with just a relay. I asked for some help in developing a circuit for this on https://forum.allaboutcircuits.com/ and can highly recommend this forum as two people pitched in with suggested circuits and others commented - some helpfully, others not so helpfully! In the end I came up with a circuit myself which was a bit more functional than those suggested, and is now working perfectly, so this is indeed possible.
If anyone is interested in doing the same, though I would caution that you need some electronics experience to do so, the full thread can be seen here:
You need to get at the small circuit board in the heater control panel to access the two connections to the momentary switch. You also need to get at the connection which drives the indicator LED. If the AC is on when the ignition is switched off, this is remembered by a control system outside the heating panel and when you put the ignition back on the AC will be switched on. This means that the connection to the LED is required so that the thermostat circuit can always detect what state the AC is in, ON or OFF, and can react accordingly otherwise it might try to switch it ON when it is already ON resulting in switching it OFF instead, and vice versa.
In the end the most difficult part of this is getting at the small circuit board in the heater control panel. A large number of screws and panels need to be removed to allow the heater control panel to be loosened and moved just enough expose the front of it to undo the clips holding on its external front cover. To do this the air vents either side of the radio need to come out, then the radio and its frame, then the top cubby or document holder, then the frame around all of these. The whole heater control panel does not need to be removed completely which would be difficult anyway as it has metal rods attached to the back to mechanically adjust air flow and direction.
I bought a spare heater control panel on eBay just to work out out to dissamble it enough to get at the circuit board. This was useful, though mine was a much later panel and the design was a bit different which led to me not pulling the knobs off straight enough. Levering one side too much more than the other caused the internal plastic light guide to crack, though I was able to repair it. After that it was fairly straightforward to make the three connections needed.
Here is the end result:
The AC control turned out to be a bit different in that the switch was not a latching one as in the headlight stalk, but a momentary one, meaning that it does not stay in an an ON or OFF position, but instead one press of the switch turns the AC on and pressing it again turns it off. It is not possible to emulate this with just a relay. I asked for some help in developing a circuit for this on https://forum.allaboutcircuits.com/ and can highly recommend this forum as two people pitched in with suggested circuits and others commented - some helpfully, others not so helpfully! In the end I came up with a circuit myself which was a bit more functional than those suggested, and is now working perfectly, so this is indeed possible.
If anyone is interested in doing the same, though I would caution that you need some electronics experience to do so, the full thread can be seen here:
You need to get at the small circuit board in the heater control panel to access the two connections to the momentary switch. You also need to get at the connection which drives the indicator LED. If the AC is on when the ignition is switched off, this is remembered by a control system outside the heating panel and when you put the ignition back on the AC will be switched on. This means that the connection to the LED is required so that the thermostat circuit can always detect what state the AC is in, ON or OFF, and can react accordingly otherwise it might try to switch it ON when it is already ON resulting in switching it OFF instead, and vice versa.
In the end the most difficult part of this is getting at the small circuit board in the heater control panel. A large number of screws and panels need to be removed to allow the heater control panel to be loosened and moved just enough expose the front of it to undo the clips holding on its external front cover. To do this the air vents either side of the radio need to come out, then the radio and its frame, then the top cubby or document holder, then the frame around all of these. The whole heater control panel does not need to be removed completely which would be difficult anyway as it has metal rods attached to the back to mechanically adjust air flow and direction.
I bought a spare heater control panel on eBay just to work out out to dissamble it enough to get at the circuit board. This was useful, though mine was a much later panel and the design was a bit different which led to me not pulling the knobs off straight enough. Levering one side too much more than the other caused the internal plastic light guide to crack, though I was able to repair it. After that it was fairly straightforward to make the three connections needed.
Here is the end result:
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