Radio Wiring

Hi all -- I have a question about the Coupe's wiring to the ISO connectors for the radio. It is standard? Nothing in the ICE FAQ suggests otherwise, but...

If so, why does the following adapter exist?

FIAT BARCHETTA BRAVA BRAVO COUPE ISO HEAD UNIT WIRING HARNESS ADAPTOR LEAD

Backstory: I have an aftermarket (Clarion) radio which seems to be draining my battery. I presume that the ignition-controlled vs direct-from-battery 12V pins are mismatched between the radio and the loom, and that is why adapters such as the above exist? Am I barking up the wrong tree?

Many thanks!

OK -- I just had a re-read of the FAQ, and there was "something to suggest otherwise" about the standard ISO connectors (my apologies!) I can only assume the aftermarket ISO-to-ISO converters must be doing the permanent-to-switched conversion described there. If anyone has any experience of them, would be great to know, it seems like the "path of least resistance" to solve my problem!

If your radio works without ignition - great, that's how the Coupe is wired from the factory. This does lead to battery drainage on newer radios, since they assume that the one of the power wires (red) is a switched, and the other (yellow) is providing constant power for memory.

Pic for reference: https://www.autofitkit.com/ebay/stereo-wiring-harness-adaptor.jpg

You don't need a new ISO connector. What you do need to do is to cut the red wire, and wire it to a switchable (ignition-on) power supply. There is one way to solve this in the how to list, but personally, I would either run a direct wire from the battery, put a fuse on it, run it inside via relay to the radio. The relay can be switched on/off by using the cigarette lighter power, or some other switched live.
You can also use the existing cable coming to the radio, just using a relay, with signal from cigarette lighter or other live to switch it on/off.
This is to prevent frying the cables due to usage of both radio and cigarette lighter at the same time, since IDK what the cable gauge or fuse is on it.

Many thanks @386ka That makes a lot of sense.

It sounds like a relay to switch the red wire according to cigarette lighter power is the way to go...

Glad to have been of any help. Btw, if you don't feel like messing with the electric installation, you can try removing the head unit when the car is turned off as an interim solution. In my case, with the HU removed, the radio draws only a small current for the memory.

I've just done this modification today! My Pure DAB head unit was slowly discharging my battery I believe.
The permanent power to the radio memory is on ISO10487 connector A pin 4. In my 2000 20VT+ this wire is solid red and should not be messed with!
The main power is on pin 7 and is a thick red/yellow wire. This is the one that should be cut and these two ends plugged into an automotive relay (15A) normally open pins.
The relay coil can be wired to the cigarette lighter power wires so that the radio is only powered when the ignition is on.