xantia radio - sony

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shaunthesheep
Posts: 364
Joined: 16 Jul 2002, 14:42

xantia radio - sony

Post by shaunthesheep » 24 Sep 2002, 22:08

hi all,
i've just checked the earth on my car stereo, using my household earth, no interference, with engine running.
put back in car ariel, interfearance from engine.
have replaced ht leads, spark plugs are NGK brand, am unsure if it's these which are causing the problem or somthing else <img src=icon_smile_sad.gif border=0 align=middle><img src=icon_smile_sad.gif border=0 align=middle>
any ideas.
dom

spanners
Posts: 77
Joined: 10 Sep 2002, 03:29

xantia radio - sony

Post by spanners » 25 Sep 2002, 00:23

there will be a resistor fitted to coil, there is also a resistor built into aerial if you have small mast(bee sting) check bonnet earth straps or could be coax cable broken down.

shaunthesheep
Posts: 364
Joined: 16 Jul 2002, 14:42

xantia radio - sony

Post by shaunthesheep » 25 Sep 2002, 01:13

cool, will do that.
forgot to mention that with the aerial unpluged got no signal whatsoever.
anyone got any ideas as to where all the earth points are, cause it sounds like a bad earth someware on the engine, would it do me anygood to clean them all up??
dom

jpeder
Posts: 12
Joined: 24 Sep 2002, 01:14

xantia radio - sony

Post by jpeder » 25 Sep 2002, 01:42

The car electrics is a closed system, so the negative on the battery should be connected to the frame ("ground") somewhere. With a potentiometer you can go through the car and find out if any of the points you suspect are "grounded" or not by measuring the difference between the point and the battery or the point and a known "ground". The difference should be zero.
Cheers, JP.

shaunthesheep
Posts: 364
Joined: 16 Jul 2002, 14:42

xantia radio - sony

Post by shaunthesheep » 25 Sep 2002, 01:55

jp, I take ip by a potentiometer, you mean a multi meter?
dom

jpeder
Posts: 12
Joined: 24 Sep 2002, 01:14

xantia radio - sony

Post by jpeder » 25 Sep 2002, 02:23

Ah, rats <img src=icon_smile_angry.gif border=0 align=middle>, is the thumb, it always hits the wrong peas. You're right, what you want is a voltmeter (multimeter). Sorry.
JP.

shaunthesheep
Posts: 364
Joined: 16 Jul 2002, 14:42

xantia radio - sony

Post by shaunthesheep » 25 Sep 2002, 02:36

thanks for the quick reply,
just a couple more questions: the multi meter i've got cost me £3.99 form lidi. i've never used one before what setting do i need it set on??
dom

shaunthesheep
Posts: 364
Joined: 16 Jul 2002, 14:42

xantia radio - sony

Post by shaunthesheep » 25 Sep 2002, 18:40

spanners,
regarding the aerial, the small 'beesting' factory fitted aerial has that got a bulit in amplifer?
dom

jpeder
Posts: 12
Joined: 24 Sep 2002, 01:14

xantia radio - sony

Post by jpeder » 25 Sep 2002, 22:47

Sorry, missed that one last night.
There are two options, one with the ignition/radio on (don't need to start the engine) and one with the ignition off. If you're just looking for "ground" switch it off. It goes something like this.
If two points on the car are in direct contact the resistance between them is very low (less than an ohm), if the points are disconnected the resistance is very high (if you're holding the metal of the probes you'll be measuring the resistance through yourself, around a few 100kohm, or if not whatever your meter shows when the probes are not touching anything).
Try it out by setting your meter to measure max. 200 ohm and hold one probe on the negative of the battery and the other on the chassis. It will read zero (no more than one) if your probes have good contact with the metal. This confirms what you already know, that the negative and chassis are in direct contact.
This is an important point, you have to know beforehand whether the points are disconnected or in direct contact, because when you then get a reading in between, you will know that it's a fuzzy connection. Start the reading at 200ohm. If it shows infinite try 200kohm. If it's still showing infinite the points are disconnected. If the reading is somewhere in between the points are connected but not very well.
<u>One clear safety tip</u>:
<b>NEVER</b> use the ammeter setting unless you know you are doing. It's effectively a shortout. And you don't want to short out <i>ANYTHING</i> on your car especially your battery. Something <b>WILL</b> explode if you do.
Happy hunting, JP.

shaunthesheep
Posts: 364
Joined: 16 Jul 2002, 14:42

xantia radio - sony

Post by shaunthesheep » 01 Oct 2002, 01:25

jp,
have checked the earth on the stereo today, meter came back with a reading of 3.2 ohms, meter was set at 200ohms this was earth wire (A8) to drivers door metal strap.
checked battery neg to frame, was 2.8 ohms, do these sound about right?? or do i need to keep on looking.
also found out that one of my earth straps on my bonnet is snapped better replace that asap.
haven't yet looked at the aerial connecion on the roof & checking
co-ax cable as this would mean removal of the head linning to make tracing fault easier.(oh what fun)
dom
also posted on xantia-L
Edited by - shaunthesheep on 30 Sep 2002 20:30:56
Edited by - shaunthesheep on 01 Oct 2002 05:33:16

jpeder
Posts: 12
Joined: 24 Sep 2002, 01:14

xantia radio - sony

Post by jpeder » 02 Oct 2002, 00:29

Hi dom,
The values sound sort of okay. I'd have guessed them to be lower though.
Check your meter by touching the probes together. Both for the ohmmeter and voltmeter the reading should be zero. If not, the value shown is the error of the reading for that dial setting.
Like Spanners said check out that bonnet strap.
Cheers, JP.

shaunthesheep
Posts: 364
Joined: 16 Jul 2002, 14:42

xantia radio - sony

Post by shaunthesheep » 04 Oct 2002, 01:00

jp,
replaced the earth strap on one side, thought i better take a look at the other one, thats now starting to wear, so will be replacing that one as well.
have been informed that my alternator might need a supresser fitted to it to cure interference, as it get's louded with the engine speed.
will keep you all updated.
dom

geoff_old

xantia radio - sony

Post by geoff_old » 12 Oct 2002, 20:44

Hello, This may or may not be of some help. My son runs a BX and has been plauged by a "lazy" starter and a small headlamp and dashlight flicker on tickover.The earth lead from the battery to engine has crimped fittings on the ends and these were found to be high resistance although to look at that did not look corroded or bad.The battery clamps were replaced and the other lead end was soldered,also the same with the lead from the negative terminal to the body.A complete cure for lights and he says that the car has never started so well. (He has owned it for 7 years.)Resistance from bat. term. to engine 2-8 ohms.
Cheers
Geoff.
G Gould

shaunthesheep
Posts: 364
Joined: 16 Jul 2002, 14:42

xantia radio - sony

Post by shaunthesheep » 13 Oct 2002, 00:11

thanks geoff, will look into that.
all,
i've now fitted a suppressor, but it did no good, i fitted it as per instructions on box, from alternator mounting bolt(earth) to 12v postive lead(thick black wire). however it did come with one of those plastic wire clamps with a build in-cutter to cut outer cable, but alternator cable might be too thick for it to cut, so might look into attaching it via a spade connecter to the 12v bolt on the alternator itself, hoping this will cure it.
will let you all know in due course.
dom
Edited by - shaunthesheep on 12 Oct 2002 20:17:27