[xj] Diode Mod, also known as the Aux Fan Mod
From Flyer94A at aol dot com
Received: Thu, 24 Jun 1999 20:19:08 +0200 (CEST)
The original
document is here.
Hi List. Here is a procedure for adding the diode so the aux fan comes on with
the compressor. This mod will cost less than $10.00. It will lower
high side pressures on cars with R-134a by 30-50 lbs when the car is not
moving, greatly enhancing cooling when stuck in traffic, and keeping the system
from blowing the hoses and seals out. It is even beneficial to R-12
and R-406 cars. The parts and supplies needed are readily available at any
Radio Shack or any electronics parts house.
Tools Needed: Soldering iron, crimping tool, wire strippers, pliers
Supplies needed: Solder (rosin core), 2 feet of insulated wire (recommend
18 gauge), diode (1N4001, 1N4002, 1N4003) or equivalent, heat shrink tubing
(assorted sizes and lengths), some type of disconnect crimp-on connectors,
male and female (spade type will do, bullet type better, aviation knife type
best but hard to find, a couple of 3-way splicing connectors if you don't
want to cut any wires).
Procedure:
1: Disconnect the negative battery cable. You will be working with/near
wires that may have power applied even with the ignition off.
2: First of all, locate the wires you will be splicing in to. On the A/C
compressor side, it is the 12 volt wire going directly to the compressor
clutch. On my car this is a green wire going directly to the clutch
plug. This
is one of the two you will be tapping into. Do NOT use the black
wire as this is ground (earth). Next, remove the plug going to the aux
fan relay (normally a red Lucas relay or maybe a black Bosch one like
mine). It's on the left side near the top of the radiator support frame
on the engine compartment side. Next locate the Green wire with a white
stripe going to this relay. It is the one farthest to the right when
plugged in and mounted normally. This is the other wire you will be
tapping into.
3: Next, make up the diode harness. Cut the length of spare wire in half,
strip one end of each wire and solder one piece to each of the two leads
coming out of the diode. (If you don't have soldering skills or equipment
you can use red butt type crimp connectors here, just make sure they are
tight). Identify the "cathode" end of the diode. It is the end with
the marker band around it. Tie a knot or otherwise mark the wire attached
to the cathode end so as not to get them confused later. Then take a piece
of heat shrink tubing just big enough around to slip over the diode and long
enough to cover all bare wire, and heat it to form insulation around the
diode. Repeat this process so as to end up with two layers covering the
diode and exposed wires.
4: Connect It. Using the three way splicing connectors or other means that
you like, connect the end you marked or tied the knot in (cathode) to the
green/white wire you located previously which goes to the connector on the
fan relay. I like to use disconnect type connectors somewhere in line
here so this can be disconnected for any troubleshooting that might be needed
in the future. Next, connect the other end of the wire attached to the
non-banded (anode) end of the diode to the green wire (previously found) going
to the compressor clutch plug, making sure the wire is routed so that it will
interfere with nothing else.
5: Test It: Reconnect the negative battery cable. Turn the Climate
control off. Start the car. Verify the Aux fan is not
running. Turn on the A/C. Verify the aux fan is running. Turn
A/C off with car running. Verify the Aux fan is not running.
Notes:
1. No additional fusing is needed as this mod simply uses the compressor
clutch power to activate the relay that powers the aux fan.
2. Some Jaguar schematics show a diode in exactly this position for this
function, although some show it opposite polarity than is needed (a misprint
I'm sure). Some later prints show it correctly.
3. Apparently, some cars come like this from the factory, mainly 12 cyl
versions.
4. This is a first draft of this procedure and I've made every effort for it
to be complete and correct. I certainly welcome any corrections,
clarifications, or better ideas.
Copyright © Steve Randall
85XJ6 with COOL A/C
From MichaelP1 at aol dot com
Received: Sun, 27 Jun 1999 03:46:56 +0200 (CEST)
Steve, I did the mod today and all is working well! I think total cost was
$4.14 for the parts! I did the connections a little different, with
excellent results. I snipped the old female connector on the green/white
wire (aux fan relay), put on a new female connector and wired both wires
(green/white; diode harness) into the new connector. The other end of the
diode harness was run directly into the compressor 3-prong fuse, to the leg
where the green wire goes into the fuse. No cutting of wires, except for
the snipping of the connector end.
Thanks again for a great post and mod...
Regards,
Mike Vaughn
