I know absolutely nothing about Auto Electronics but as some of you may know, I am in the process of trying to Start 'Carmen' my 1995 XJS 4.0L Convertible with AJ16 6 cylinder engine
Having already changed the CPS and put in 6 New Injectors, I then checked every single fuse I could find which turned out to all be OK and even removed the ECU to clean all the Pins
But Still no go
Though something has been bugging me, when 'Paddy' one of our Forum Members had a similar 'No Start Problem' on his Car, where someone suggested that he Changed the 'Blue Relay' in the Footwell
Where once having done so his Car Started straight away, after which I started looking in the Footwell of my own Car to find it, except I couldn't see it in the Footwell anywhere
But after hunting high and low for something unrelated, as if by some miracle I found my Owners Manual for this Car, where that Relay I've been looking for is 'Sort of' in the Footwell although its much more higher up, where the Fuses are
And as such in the only place that I wasn't looking, although I've found it now!
Where according to the Owners Manual, this is the RELAY FOR THE ECU! OMG! I'm thinking, how good could that be!
Where while having so many false hopes dashed into the ground, I'm daring to dream that maybe this is the Missing Link, that might just get her running after trying everything else
And so what I would like to do is Test it and hopefully find that it's 'Toast'
So here are some Pics of that Relay in the hope that someone will be able to show me how to Test it
If someone could give me the Pin Numbers of what I should connect my Meter to, then I can give it a Test and see what comes out
It doesn't say what Value it is, except that the Part Number on it is DAC7686
Would I be able to Swap it for one of those Black ones that I took from my Parts Car which has the same Pin Layout but no other numbers that I am able to read
According to the Handbook the Blue Relay on the Left is the ECU Relay although it doesn't seem to say what the Blue Relay on the White Base to the Right of it is for, so if they are part of the same thing Swapping them over might not do any good
I think I've got some Black Relays with that Alternative Number on them, so I better replace the other one as well, in case they work together in some way
Alex, to test the relay check for 12v between pins 85 & 86, if you have 12v the relay should click on, then you should have voltage on both pins 80 and 87 to ground.
I you replace it that relay has a snubber diode, make sure the new relay has the diode the same way between pins 85 and 86, the band goes towards the + terminal. The diode loops back the voltage spike when the relay turns off and it is important that the diode polarity is correct or you will blow a fuse or cook the diode.
Alex, to test the relay check for 12v between pins 85 & 86, if you have 12v the relay should click on, then you should have voltage on both pins 80 and 87 to ground.
I you replace it that relay has a snubber diode, make sure the new relay has the diode the same way between pins 85 and 86, the band goes towards the + terminal. The diode loops back the voltage spike when the relay turns off and it is important that the diode polarity is correct or you will blow a fuse or cook the diode.
Hi Warrjon
Cheers!
The Black Relay has a diagram on it but its very hard to read even with a Magnifying Glass but I think I can just make sense of it, so lets hope it works
the relay is basically a mechanical switch that uses a electro magnet coil to move the mechanical switch, if you energize the coil with power and ground on 86 and 86 you should have continuity between pins 30 and 87, the contacts on the switch can get burned or corroded over time and not make good contact. the easiest test is to just swap it for a known good relay and if that's not the problem you can just swap it back.
Excellent! Just the kind of info that I was looking for!
When I swapped those Blue Relays round She started straight away, so maybe the act of swapping them over was enough to get them to make proper Contact, as in the info I got from the Relay update from 'Motorcarman'
Not that it seems to matter now but I still don't know what that Blue Relay sitting on the White Base does, I can't find any mention of it in the Owners Manual
This thread is a great dissertation on relays and how they work. I've always been intrigued by them. Way back to the days of weak 6v head lams on old cars. A relay install helped tons!!
To do electrics on these Jaguars an electric schematic is an absoluter necessity.
And, indeed as here, merely removing and installing cleans contacts. Good parts re tossed !
A relay has two circuits. The trigger circuit and the load circuit, The first connects the latter electricaly.
