Blowers were working fine and suddenly quit. 50 amp fuse okay,
large relay will click when I pull off the connectors on several
pins. What can I check?? Is that the only relay? I followed my
wiring diagram and it doesn’t show any.
50A Fuse, relay, resistors, blowers … thats it; save the wrath of
Have you got a meter to measure the voltages at various intermediate
points? I suggest checking at each available point for power/ground
voltages. This is really the easiest and most effective way of testing
the system. You may need some small jumper wires to play with some of
the subsystems (more below about cycling through all the relays).
The fuse and it’s connections generate a lot of heat, the fuse holder
itself can melt and reduce the clamping pressure, and/or the contacts
can get corroded enough that even an apparent proper fuse connection is
simply moot. This failure has bit me more than once, clean the fuse
The large relay is brittle inside, if you have enough courage you could
pry the cover dimples and disassemble it and make sure that all relay
contacts are cleaned with appropriate contact cleaners, beware of the
windings, they are easy to break. However, this source of the problem
is usually a gradual failure, not all of a sudden like yours.
You have several choices here to cycle through all the relays, pick one
(from less invasive to most):
You could try to run the system through it’s paces with the
temperature control knob, flawed only in that there are overrides at
various levels of the circuit that could cause the appearance of
failure and the difficult to ascertain if the servo unit has in fact
gone through it’s complete cycle from end to end. Listen carefully as
each relay operates.
Disconnect the round A/C amplifier connector and on the end going to
the car jumper #1 (Purple) to Power (#3 brown) and #2 (Red) to Ground,
then alternately #1 to ground and #2 to power feed (yes reverse). This
allows one to run the servo assembly through it’s complete cycle.
A Definitive test mainly because there is a temperature disconnect
that prevents some of the relays to activate. On large relay,
disconnect #14, #11, #8, #86 and #E. Be careful to remember which wires
are which for when you reconnect. Ground #E with a jumper (this will
override the temperature disconnect). One at a time, connect a battery
feed from 21A or 3/51 to #14, #11, #8 and #86 to see if each relay
works and check if the fan operates.
Sincerely – Mark SalyzynOn Monday, September 2, 2002, at 10:55 PM, terjer wrote:
The archives and FAQ will answer many queries on the XJ series…
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