Any auto electricians out there?

[swee'pea99]

Hi

Thanks for sticking with me. Sorry it's so stop-start...I have to have goes when I can find a minute. Ok:

Yes, the yellow wire was giving me 1.7v - tho' it's zero now. (I haven't changed anything in between times.)
No, the yellow wire has no white stripe - it's just plain yellow.
I'm pretty sure it's not a speed-sensitive volume adjuster - I never had one before, and I don't think anything so fancy was ever fitted to this near-20 year old Golf.
I'm certain it's 'the true yellow wire'.

One sideways question - if I wanted to check the new unit just to make sure I haven't somehow fried it completely, by connecting it directly to the battery, which wires should I connect? Red & black/pos & neg?

 

[Chromatic]

I gather you've had it in and working at one point, except for the aerial connection which prevented the radio working, and since having it out to connect aerial then in again you've been unable to get anything out of it at all, is that right?
Is there an internal fuse in the unit which has gone? This was the problem I encountered a while ago when daughter asked me to have a look at her car stereo that wasn't working, there was a mini blade fuse in the rear of the unit that for some reason had blown when changing the car battery.

 

[simon the viking]

Red and yellow to plus And black to minus
Hope that helps and good luck_

 

[swee'pea99]

Yes, I'm back again! Finally found time for a bit more fiddling, and....

First off, many thanks for your suggestions and help. Really appreciate it.

Second off, it's not the unit fuse. I know this because following your suggestions, I connected the red & yellow and attached them to the battery +, and the black to the battery -, and the thing came to life! Hooray!

Next, I connected the red & yellows inside the car in the same way: ie, red+yellow connected to red+yellow, and ta-da! the thing came to life, again! So, clearly there is power. And the unit works. But obviously I can't just connect it like that, because it'll be on permanently, and drain the battery. So, I unbundle the yellow+reds, and connect red>red and yellow>yellow. Nothing. Dead as the proverbial. Interesting. And this is regardless of whether the ignition is on or off.

So, I go back to the wires, and, there's a dual core cable, separate from all the others, which comes from the right-hand side of the hole in the dash, and seems certain to be the one that's going to the ignition. Presumably (I presumed) this one manages the whole ignition off>off, ignition on>on business.

One of these two wires is black. That one is simple: it's just joined to the back in the main bundle. Earth, presumably. The other is red, so I'm guessing it's the one that carries the current to activate the unit when the ignition is switched on. So I follow it back, to where it connects (with a rather odd connector) to a pink wire, that then goes back into the main bundle of wires. A picture might help at this point...

1 is the red wire, 2 is the pink. The pink goes into the main bundle at 3. From which emerges (among others) a yellow wire (at 3) which connects directly to a red wire at 4 - this being the red wire that goes into the wiring loom, and on to the unit. And also a red wire (5), which goes into a blue connector, along with a red & white wire that has come out of a different bundle, with the yellow (loom) wire emerging from the other end.

All clear? As mud. Right.

Anyway, I'm thinking, assuming that the two-core cable that comes out from the ignition is the one that manages the whole ignition off>off, ignition on>on business, and assuming also that the black cable is the earth, then presumably the red one should have 0v when the ignition is off, but 12v when it's on. So I get out the micrometer, jam the probe into the other end of the blue connector (the one at 1, where the red wire is joined to the pink one) and test for a reading. 0v. Then I turn the ignition on. 0v.

So, does this tell me anything? Or is my assumption about the on/off = 12v/0v incorrect?

I tell you, I'll never moan about adjusting gears again after this...

 

[simon the viking]

The pink could be a power aerial feed therefore 12v meant to go down it not come from it.... not sure

When you said you connected red+yellow and red + yellow together did you mean all 4 wires joined together in one connection inside the car?

 

[swee'pea99]

The pink could be a power aerial feed therefore 12v meant to go down it not come from it.... not sure

When you said you connected red+yellow and red + yellow together did you mean all 4 wires joined together in one connection inside the car?

Interesting...about the pink. That sounds likely, though I haven't had an aerial since it got snapped off over a decade ago - I don't listen to the radio myself. But my guess was that the 12v would be coming from the (ignition-attached) red and going to the pink (and then on to the main unit-side power leads).

And yes, re the red+yellows: I got a single one of these,

jammed the red+yellow together into a hole and screwed tight, then the other red+yellow in the other end, screwed tight.

 

[simon the viking]

Hve you tried red to yellow in one block and red to yellow in the other? ie switched the 2 colours?

 

[swee'pea99]

Nope. Should I?

 

[simon the viking]

Yes try it, should work.

 

[swee'pea99]

Thanks. I will. But I'll do that tomorrow. It's a bit dark to be fiddling with wires right now - it's bad enough in daylight!

 

[simon the viking]

okey dokey.... let us know what happens

 

[swee'pea99]

I will. And thanks again.

 

[swee'pea99]

Ok, tried that. No joy. Just nothing. Dead as.

So I tried my old trick again, of cramming both (dash) red+yellow into one hole, then both (unit) red+yellow in the other, and - it works! Or at least appears to. It works perfectly, plus everything goes off when the ignition is turned off - no lights, no nothing. Does that mean it won't drain the battery if I leave it like that? I'd sorely love to just shove it back in the dashboard now that everything seems to work fine (plus I've now been without music for a fortnight). But I don't want to if it would mean draining the battery.

 

[simon the viking]

IF (note the word IF) this was my car........ I would go with connecting it like you have if it works but bare in mind the following...
- make sure the connection is firm and tight in the choc-block then insulate each end with insulation tape
- Hopefully the red and yellow both have fuses holders between the connection and the stereo (if they haven't then I would think about putting one in both cable)
- if the front is removable then remove it whenever parked as this will help kill the power and lesson the chance of a flat battery

SERIOUS DISCLAIMER THOUGH....... I am not an auto electrician and therefore not really qualified to advise you.... but I have done a few big installs and sold car audio for many years

Hope it works ok

 

[swee'pea99]

IF (note the word IF) this was my car........ I would go with connecting it like you have if it works but bare in mind the following...
- make sure the connection is firm and tight in the choc-block then insulate each end with insulation tape
- Hopefully the red and yellow both have fuses holders between the connection and the stereo (if they haven't then I would think about putting one in both cable)
- if the front is removable then remove it whenever parked as this will help kill the power and lesson the chance of a flat battery

SERIOUS DISCLAIMER THOUGH....... I am not an auto electrician and therefore not really qualified to advise you.... but I have done a few big installs and sold car audio for many years

Hope it works ok

Many thanks - really appreciate you sticking with me all this way. When 'er indores calls me up from a service station on the M4 moaning on about a deid car, I'll give her your number.

Oh, incidentally, they do both have fuse holders. Thanks again.