[xj40] How to find shorts in circuit boards?

XJ40
1

I took both of the rear BFM’s out of my car because the turn
signals did not work when I apply the brakes. I pulled them apart
expecting to find obvious signs where a short had occurred. I’ve
been told that shorts show up as gray joints with circles around
them. Both of my BFM’s looked like new inside. Am I blind or is
there something I’m missing?–
wylde8
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

2

When I did mine on my '88 XJ40, there was no indication of a break or where
the bad joint could be. I re-flowed them all and must have gotten to right
one because the problem went away.

Clark
'88 XJ40
'67 S-Type
'67 420----- Original Message -----
From: “wylde8” wylde8@hotmail.com
To: xj40@jag-lovers.org
Sent: Friday, December 20, 2002 7:43 PM
Subject: [xj40] How to find shorts in circuit boards?

I took both of the rear BFM’s out of my car because the turn
signals did not work when I apply the brakes. I pulled them apart
expecting to find obvious signs where a short had occurred. I’ve
been told that shorts show up as gray joints with circles around
them. Both of my BFM’s looked like new inside. Am I blind or is
there something I’m missing?

wylde8
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

3

I think you are confusing the description of a short with a cold solder
joint.
You often can’t really see a cold solder joint and if you suspect one you
probably should just reflow them.
A short circuit with enough current will result in a blown fuse, burned
trace or other blown component.----- Original Message -----
From: “wylde8” wylde8@hotmail.com
To: xj40@jag-lovers.org
Sent: Friday, December 20, 2002 7:43 PM
Subject: [xj40] How to find shorts in circuit boards?

I took both of the rear BFM’s out of my car because the turn
signals did not work when I apply the brakes. I pulled them apart
expecting to find obvious signs where a short had occurred. I’ve
been told that shorts show up as gray joints with circles around
them. Both of my BFM’s looked like new inside. Am I blind or is
there something I’m missing?

wylde8
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

4

Wylde,
Check also rear light clusters.Boards where the bulbs are
mounted.
Rgds:Jukka
XJ40 Sovereign 3.6 -89 MANX 179900km----- Original Message -----
From: “wylde8” wylde8@hotmail.com
To: xj40@jag-lovers.org
Sent: Saturday, December 21, 2002 2:43 AM
Subject: [xj40] How to find shorts in circuit boards?

I took both of the rear BFM’s out of my car because the turn
signals did not work when I apply the brakes. I pulled them apart
expecting to find obvious signs where a short had occurred. I’ve
been told that shorts show up as gray joints with circles around
them. Both of my BFM’s looked like new inside. Am I blind or is
there something I’m missing?

wylde8
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

5

In reply to a message from wylde8 sent Sat 21 Dec 2002:

Thanks for the great responses everyone. This will also help me
with my wiper module and my instrument cluster. If anyone else has
advice, please chime in.–
wylde8
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

6

With a bright light and a big magnifier, you can sometimes
see them, but its better and easier to just resolder all the relay
joints and the connector joints where the
small board plugs onto the big one.

Its no coincidence that most problems went away after the design
did away with the separate boards inside the BFM.
(around 1993?)

Brett
1990 XJ6>

I took both of the rear BFM’s out of my car because the turn
signals did not work when I apply the brakes. I pulled them apart
expecting to find obvious signs where a short had occurred. I’ve
been told that shorts show up as gray joints with circles around
them. Both of my BFM’s looked like new inside. Am I blind or is
there something I’m missing?

wylde8
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–