1983 XJS HE. I am in need of an explanation of the wiring of the
tachometer. Can anyone tell me where the wire comes out of the
firewall and then where it goes. I know that I have a loose wire
just by the way the tach moves around. It is fine until engine
warms up. Once warm need drops to zero then will just bop around.
However, when I hit a bump the needle will jump, be ok for a little
while, then drop again. Thank you all for any assistance.
I can’t trace the wire all the way from the engine harness to the
instrument cluster, but the amplifier provides the signal for the tach.
There are four wires that come out of the amplifier case on the
inboard side, toward the center of the engine. The one that provides
the tach signal is White/Slate/Blue (WSU), and if you follow that wire
from the amplifier case (black case on top of left intake manifold) you
should find a bullet connector and then the wire goes into the engine
harness, running rearward.
The harness runs to the rear of the engine, then to the right side of
the firewall at the A pilar, and then into the bulkhead harness across
the inside of the car to the instrument cluster.
The most likely places where you might have a loose connection are:
(1) in the amplifier itself;
(2) at the bullet connector a few inches from the amplifier;
(3) at the attachment of the WSU wire to the tach in the instrument
cluster;
(4) anywhere else in the path described above.
Please let us know what you find.
George Balthrop, Clifton, VA USA
89 and 85 XJ-S Coupes; 89 XJ40 VDP-----Original Message-----
From: Crusader erando6077@aol.com
1983 XJS HE. I am in need of an explanation of the wiring of the
tachometer.
In reply to a message from George Balthrop sent Mon 9 Jul 2012:
Good evening George. Here is what I did. The connection at the
ignition amplifier appears to be good and tight. I then checked
the bullet connector to the tach wire. I pulled the connector
apart and the connection was very greasy. I cleaned the grease and
reconnected the wires. When driving the next day the tach was
working splendidly then I hit a bump and the tach went crazy
again. After getting home I lifted the bonnet and checked the
bullet connector again. Interestingly enough it I was able to sort
of spin the bullet connector and then it got tight. I then thought
that perhaps the signal wire connector was not making a tight
connection to the tach wire. I left the connetor in what I will
call the tightened position and will see what happens the following
day. If what I have done does not work then I will at some point
check the connection to the tach itself as that may be the
problem. Thank you for your assistance.
Eric–
The original message included these comments:
I can’t trace the wire all the way from the engine harness to the
instrument cluster, but the amplifier provides the signal for the tach.