Electro guru needed

bernie · Post by **bernie** » 22 Jun 2005, 20:01

How would you test a diode that is connected in parrallel to a relay coil?
nb. the diode cannot be disconnected.

ActivaV6uk · Post by **ActivaV6uk** » 22 Jun 2005, 21:09

Tell me what car/year/engine and i may beable to help.
Andy

Kowalski · Post by **Kowalski** » 22 Jun 2005, 21:20

Ideally you'd use a component tester, a place I used to work at had one. Basically, it had a CRT and a couple of probes and it applied an voltage to the component and drew on the screen a sort of graph.
In abscence of a proper tester, have you tried checking the resistance in one direction then swapping the terminals over and seeing what the resistance is like in the other? With the diode in parallel to the coil, one direction should give the coil resistance (i.e. the diode doesn't conduct) and the other would give the coil / diode parallel resistance (i.e. the diode does conduct) which should be pretty low. An infinite resitance in one direction and no resistance in the other would indicate that the coil is shot, the same resistance in both directions would indicate that the diode is dead, you're looking for a coil resitance in one direction and a low (diode forward bias) resistance in the other.

bernie · Post by **bernie** » 22 Jun 2005, 23:56

Andy it's the electro valve on the HA2 block. ha ha
Kowalski (wern't you in Voyage to the bottom of the sea?) I'm getting 4.2 ohms each way so I thought the diode was shot but I was not sure about the readings in parrallel

Kowalski · Post by **Kowalski** » 23 Jun 2005, 03:48

Sounds like your diode is shot.
Kowalski was in Vanishing Point.

dnsey · Post by **dnsey** » 23 Jun 2005, 04:09

Adding another diode will do no harm (as long as it's the right way round!), even if the original's OK.

bxbodger · Post by **bxbodger** » 23 Jun 2005, 20:14

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Kowalski was in Vanishing Point.<hr height="1" noshade id="quote"></blockquote id="quote">
And Voyage to the bottom of the sea! He was the stroppy sidekick if I remember rightly, the Captain always shouting "get the lead out, Kowalski...."

Kowalski · Post by **Kowalski** » 24 Jun 2005, 00:49

Was he the one who got attacked by the sea monster each week....

tomsheppard · Post by **tomsheppard** » 25 Jun 2005, 03:17

And if the original is short? Call me please, Bernie.

Post by **Richard Green** » 25 Jun 2005, 03:40

no Kawolski that was voyage to the bottom of the pee or some thing like that, diodes like to work as a team so when one dies it takes more out sort of like a ring main in a house for lights and just as complicated.

Stempy · Post by **Stempy** » 25 Jun 2005, 04:07

Diodes go short when too much current is passed through them and open when too much voltage is applied across them.

Kowalski · Post by **Kowalski** » 25 Jun 2005, 04:13

Obviously the smoke seal's gone which is why the smoke came out. If you replace the seal and recharge the smoke it'll probably be as good as new
bofh

Post by **Richard Green** » 25 Jun 2005, 04:35

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Stempy

Diodes go short when too much current is passed through them and open when too much voltage is applied across them.
<hr height="1" noshade id="quote"></blockquote id="quote">
thats why diodes/capasitors are fitted to equal the flow of voltage.

Post by **Richard Green** » 25 Jun 2005, 04:41

i forgot resistors, minds on flip number plates.

Stempy · Post by **Stempy** » 25 Jun 2005, 04:58

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Richard Green

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Stempy

Diodes go short when too much current is passed through them and open when too much voltage is applied across them.
<hr height="1" noshade id="quote"></blockquote id="quote">
thats why diodes/capasitors are fitted to equal the flow of voltage.
<hr height="1" noshade id="quote"></blockquote id="quote">
Just to be a pedant, voltage never flowed anywhere, current flows, voltage is potential difference[8D]