Head Unit wiring

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saintjamesy89
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Head Unit wiring

Post by saintjamesy89 » Thu May 25, 2017 9:39 am

Hi all,

I've read a couple of previous threads about wiring in a new head unit but have a couple of questions that I hope the wise among us can answer. Need to get the head unit in and working this weekend before the challenge (next Friday). The new HU looks like it uses the permanent feed as the main feed (this wire is fused).

-For the standard radio, is the main feed switched or constant? (seem to remember being able to turn the radio on without gnition on, suggesting constant)
-Is the clear plastic thingy inline with the fuse just before connecting to the radio a relay? It is full of coiled wire. Not sure whether to use it or ditch it with the new HU (see my blog for piccies).
-Does the standard radio have an earth? There wasn't an abvious one that I coculd see. Could use the earth point that the temp gauge uses, it isn't far from the HU.
-If the original radio live is constant, could I piggy back a switched feed from the recently fitted temp gauge or would the ciggy lighter be better?

Thanks guys.
I'm not a Saint, or a James, but a Tom Saint-James!

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RobC
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Re: Head Unit wiring

Post by RobC » Thu May 25, 2017 10:20 am

I can't answer all your questions, but the cigarette lighter is also unswitched. I can't remember where I got my switched feed from - maybe the clock? Modern head units often also have an option to dim their display when the headlights are on, and the clock is a good place to get this feed from too.

Earths can go anywhere as long as it's earth!
Standard radio was unswitched yes.
1991 Citroen BX 16v

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Re: Head Unit wiring

Post by saintjamesy89 » Thu May 25, 2017 10:26 am

Ok, cheers Rob, that clears things up a bit. My MK1 has its clock as part of the trip computer, so a bit more tricky. Not sure I want to mess with that too much, it works atm.

Rich fitted a temp guage for me recently, so may have a see where that gets it's switched live from - and use that.
I'm not a Saint, or a James, but a Tom Saint-James!

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Re: Head Unit wiring

Post by Kitch » Thu May 25, 2017 2:31 pm

saintjamesy89 wrote:Ok, cheers Rob, that clears things up a bit. My MK1 has its clock as part of the trip computer, so a bit more tricky. Not sure I want to mess with that too much, it works atm.

Rich fitted a temp guage for me recently, so may have a see where that gets it's switched live from - and use that.


From the dimmer reostat on the steering column cowling. :) Don't earth through it though, go direct!

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Re: Head Unit wiring

Post by saintjamesy89 » Thu May 25, 2017 6:03 pm

I thought i'd earth using the same point as the temp gauge (the bolt on the steering column bracket), using another little ring-connector. Is that direct?
I'm not a Saint, or a James, but a Tom Saint-James!

Mes voitures:
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Re: Head Unit wiring

Post by Kitch » Thu May 25, 2017 8:36 pm

saintjamesy89 wrote:I thought i'd earth using the same point as the temp gauge (the bolt on the steering column bracket), using another little ring-connector. Is that direct?


That's fine, although your current stereo wiring should already have an earth you can use. That said, I seem to remember (could be hazy here) that some of them used the aerial as an earth, so could try it like that.

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Re: Head Unit wiring

Post by saintjamesy89 » Thu May 25, 2017 9:37 pm

I couldn't find an obvious earth, there only seemed to be power, l speaker, r speaker and the aerial plugged into the back. Lol aerial as an earth? SOunds like it'd upset radio signal.

There was a yellow cable taped to the unswitched feed that didn't connect to anything though, haven't got any wiring diagrams here at home to see what that one is.
I'm not a Saint, or a James, but a Tom Saint-James!

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Re: Head Unit wiring

Post by Jaba » Fri May 26, 2017 8:33 am

Here a few thoughts of mine which may or may not help.
I have always put in a new clean earth for head units, especially on a petrol car for noise suppression. Finding a switched live that worked on the first click on the ignition was always a bit of a challenge whereas a permanent live was easy. The permanent live was need to keep the memory working on one or two of the sets I have used. I seem to recall that I have bought an ISO connector to use for ease of connection. I could find a pin out I expect if needed.
Happy listening.
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Re: Head Unit wiring

Post by Kitch » Fri May 26, 2017 12:06 pm

You need a permanent live for the memory anyway, but having the turn the thing on and off myself is one of the things I hate about my 16v! I've been meaning to wire it off a switched live for years.

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Re: Head Unit wiring

Post by saintjamesy89 » Sat May 27, 2017 1:50 pm

Fitted and fully functional :D Can't help but being a little bit proud of myself. Definitely need some new speakers now though! Will update the blog later for more info and pictures.
I'm not a Saint, or a James, but a Tom Saint-James!

Mes voitures:
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Re: Head Unit wiring

Post by Tim Leech » Sat May 27, 2017 5:59 pm

Hi Tom

You can probably just replace the base unit under the dash as I did, a whole £12 from Halfords and a straight swop.
1963 VW BEETLE 1200
1985 BX 19GT Mk1
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1994 Xantia 1.8i SX
1972 Morris Marina 1.8 SDL
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Re: Head Unit wiring

Post by saintjamesy89 » Sat May 27, 2017 6:42 pm

The bIg speaker is not working I don't think (unless it doesn't put much sound out), the two little 2" mini speakers seem to be not too bad though - considering they're likely 32 years old!
I'm not a Saint, or a James, but a Tom Saint-James!

Mes voitures:
1985 Citroen BX19 GT
1988 Volvo 740 2.0 GL Hearse
2002 NIssan Micra 1.0 S CVT
2012 Kia Venga 1.4 CRDI

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Tim Leech
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1979 Rover SD1 3.5 V8-S TSL 982
1980 Morris Marina 1.7HL DBV468W
1985 CITROEN BX 19GT C1TBX
1991 CITROEN BX 19TZI AUTO A/C BXi 19
1994 CITROEN XANTIA 1.8 SXi M908HRY
2002 Rover 75 CDT Connossieur SE Nav Auto R40TSL
2003 Rover 25 1.6i XL L33CHT
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Re: Head Unit wiring

Post by Tim Leech » Sat May 27, 2017 7:27 pm

That's all I changed, my tweeters still work well, it's just two nuts and the speaker housing will pull down and you then take it apart and the speaker is 4 screws.
1963 VW BEETLE 1200
1985 BX 19GT Mk1
1991 BX 19TZI Auto A/C
1994 Xantia 1.8i SX
1972 Morris Marina 1.8 SDL
1979 Rover SD1 V8-S
1980 Morris Marina 1.7HL
2002 Rover 75 CDTi Connossieur SE AUTO Nav
2003 Rover 25 1.6i XL 5 DR

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Re: Head Unit wiring

Post by saintjamesy89 » Sat May 27, 2017 9:27 pm

After a bit of use, the small speakers actually aren't that bad - im regretting rushing buying new tweeters now! Would have lasted the challenge at least. I've spent, and then spent some more on this car int he last month or two, so really don;t need to do any more spending! Also i'd like to have a proper review of the speakers, including wiring in some rear ones in the future so I think i'll leave the under-dash one (have thoughts of replacing it with a woofer) for now as it is either not working or not objectionable.

Many thanks to all those that helped in my wiring queries! Using the existing wires from the radio, and the easy to find locations Rich used for the temp gauge (earth and switched live) made not too bad a job of it at all.
I'm not a Saint, or a James, but a Tom Saint-James!

Mes voitures:
1985 Citroen BX19 GT
1988 Volvo 740 2.0 GL Hearse
2002 NIssan Micra 1.0 S CVT
2012 Kia Venga 1.4 CRDI