Hi guys, new to the forums. I have a problem with my 56 plate jaguar Xtype 2.2 diesel. I have a problem with the fuse box. The full beam is on constant unless I remove the fuse, it will not dip with the fuse in. The glow plug light is on and the cruise control not activated light is on and the car is hunting on idle. It nearly dies then revs up and then drops.

I have located where the buzz is from and it’s from the relay located R5. The car was running fine until I tried to change a relay for the right hand side light relay.

just wondering if anyone has any advice.

 

Hi perryrc1,

Sorry but the 56 plate reference doesn't mean anything to me....what year of manufacture is your car?

Relay R5, is that located in the power distribution fuse box underneath the bonnet?
There is also an R5 relay in some variants of the passenger junction fuse box as well.

I don't see a right headlamp relay in the schematic...fuses yes, but no specific relay for left or right headlights.
Can you please confirm which relays you moved about that ended up inducing your problem?

 

hi,

sorry it’s a 2007 model. The fuse box is located in the bonnet yes. I tried to bypass the R1 by using a wire from terminal 3 to 5 but used 3 to 4 by mistake. I did this to test if it was the R1 fuse to see if the right hand headlight would work. Now it idles rough with the glow plug light showing, full beam on constant and cruise control not activated warning light. Everything else works. The R5 fuse is buzzing and I tried to swap it with another similar fuse and still makes the noise.

 

Hi perryrc1,

Relay R1 is the main beam headlight relay.....your test to bypass R1 contacts by linking pins 3 to 5 should have brought headlghts on as you thought, but bridging between pins 3 to 4 instead would have only powered up the fog lights instead, but only if the headlight switch was also in the pulled out state for fog lights front or rear.
I can't see a way that linking pins 3 to 4 on R1 could cause the issues you have.

Question: You say you can hear R5 relay in the power distribution fuse box making a buzzing noise, can you check the passenger compartment fuse box for its relay R5 to see if that too is buzzing or ticking like the relay under the bonnet?

Relays only make that sound if their coil current is being interrupted, either by supply voltage fluctuation or they have a faulty earth to them.
With ignition off, check the resistance from pin 2 of relay 5 socket to chassis earth. If that measures above 2 ohms, then you likely have a bad earth wire or earthing point (G14) located just behind the power distribution fuse box. Both the earthing point, lugs and the wire are very close to the brake servo, so are susceptible to tainting and corrosion.

With R5 relay rapidly "buzzing" currently, I am not surprised that you might have some downstream electronic misbehavior. If you can get that relay to stabilize, I am hopeful the car may settle down.

 

Yeah it’s really strange. So these are the lights on the dash that keep coming up; glow plugs, abs, cruise control. The full beam is on constant regardless of the relay in. The engine revs up then nearly dies before revving up again. When I turn it off and pull the key out the engine is still on but turns off 2 or 3 seconds later then the climate control turns on without the key in the ignition. I have to pull the R5 relay in the engine bay out to turn the climate control off.

it’s really strange. I’m not sure if it’s the fuse box or the ECU is gone?

 

Hi perryrc1,

Sorry for the delayed response.
I'm going to have to think on this one a bit...not much makes any sense with that odd behavior.

Do you have a digital test meter (Multi Meter) that can measure 12 volts and also check for resistance measurements (Ohms testing)?

I recommend the first place to start is to establish an electrical baseline by having you sequentially pull each fuse out one by one from the power distribution fuse box and measure it to be sure every fuse is intact (not open circuit).
One by one is easiest so you do not get muddled up and can property note any failures.
Note any fuses that have failed by their size and fuse assignment number from the owner manual or schematic, so we can then try to establish a failure pathway and possible sensors or module that might be affected.
Once you have gone through that fuse box, then do the same with the passenger compartment fuse box.....check each fuse one at a time.
Let us know once you have managed to do that and if you find any failed fuses.

In the meantime I will put my thinking cap on as to a logical testing procedure or instructional steps for you to take as we try to work through getting a better understanding of this car's issues.

I feel we might be in for a journey on this one and I do not have the Diesel variant myself, so am not fully familiar with its nuances.....but I am told god does love a trier.....so if you have the time and patience, let's see if we can start to narrow things down a bit for you.

 

Relay R5 in the power distribution box likely can only "buzz" if the coil is being switched rapidly on and off creating the mechanical noise you are hearing (and likely feeling if you put a finger on the relay's casing).
As the R5 coil is receiving it's power via the integrated fuse box relay R13 (Slave ignition relay), then either that relay is pulsating too, or we have an earthing issue as they both share a common earthing wire and grounding point (mentioned in earlier posting).

To describe the ignition circuit in more detail, R5 only gets it coil power via R13 contacts which is simply being drive from the interia switch engagement (RHS A pillar), which in turn is only receiving power once the ignition switch is rolled into Run position 2.

So to try to ascertain if your R5 buzzing behavior is creating electrical interference to the sensitive modules downstream, it might be worth doing an R5 isolation/bypass test.
With ignition turned off, remove R5 from the power distribution box and prepare a link (a beefy toggle switch (20 amp) would be ideal with some wires attached, but a suitably hefty wire link will do if you have a second set of hands available) that will insert between pins 3 and 5 of the vacant R5 relay position.
Starting with the R5 link out (or your test switch open), roll ignition switch to position one, then co-ordinate in relative unison rolling ignition to position two and simultaneously insert the R5 link (or flick your test switch) that is making the connections between pins 3 & 5 of the relay R5.
If the car's instrumentation is working normally, headlights behaving etc, then you might try starting the car for a very brief stationery run test by rolling the ignition key to start position.
To turn it off, you will need to simultaneously roll the ignition key back from position two towards the off position, but also at the same time undo the R5 link to simulate the ignition relay release.

If everything behaved normally, engine not hunting and all the electronics were normal, then we need to circle back to nut out why R5 is physically buzzing.

Good luck with the diagnostics....keep in touch.