This ain't no relay

While trying to diagnose a problem with my cooling fan I was swapping the relays on the LHS wiring box at the front wing to see if a bad relay was the problem. Came across this critter, obviously not a relay, it doesn’t have the standard 86/85 numbering system - some kind of diode pack? There is no part number on it. More importantly, where does it go back? I removed most of the 6 blue relays in that bank next to the small fuse box, now I’m not sure which one is the location of the thing that looks just like a relay.

Why would you make something with the exact same pin configuration as a relay, that isn’t a relay? Lucas, I’m, looking at you.

The infamous diode pack. Allows the fan switch to operate the aux fan without backfeeding the A/C compressor. Standard, but yours is a bit darker blue than I recall. Mine was more of a sky blue.

BTW, I suggest you change your attitude about relays. Lots of them are different in this car, just swapping them around willy-nilly is a recipe for malfunctions that nobody will be able to figure out.

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What year is your XJ-S/XJS and what engine is in it?


It’s a 1992 XJR-S, with the JaguarSport 6.0L engine.

Sorry, but I don’t know anything about those cars and don’t have any facelift documents that would help, like a MY92 S-57 Electrical Guide or Parts Catalogue. As Kirby points out there are lots of electrical components that will fit that connectors and a variety of different kinds of relays and diode packs that will fit. Some relays have timers, others have diodes or capacitors all for different purposes. Just because they fit doesn’t mean they will work.
I take lots of pictures and keep detailed notes when I remove and replace components to make sure that I put things back where they belong. Perhaps you should consider doing this in the future.

Maybe someone with a 1992 MY car and documents can help.


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So they fit in standard sockets? Just a guess.

Better look at Bosch, Pektron, and Hella as well :slight_smile:



It’s Pektron. After cleaning off the grime there is a part number E2892. In the clear light of day, and having removed all the relays, it is obvious that the first 4 blue sockets have only 4 connectors wired up (30, 85, 86, 87), which matches each of 4 identical relays (Hella 4RA 003 510-68 / Jaguar DAC7686). The cuckoo in the nest at position 5 is going to be the diode pack. The socket is a different colour, but it is a pretty shonky arrangement to have the exact same pin configuration as a relay.

Internally it has two PE850s on pins 2, 4 & 5. I can’t find a datasheet for that diode, but they look much like any IN4000 series diode, with a forward voltage of 0.5v. The other one, on pins 1 & 3, is a more exotic, BYT77 fast avalanche sinterglass diode. But it is not wired up to anything, the socket does not have connections for those two pins. Internally the circuit board says 0223 AY1A on one side, and WASH WIPE on the other. I guess I should check the headlamp/washer system as a possible circuit that it is part of. Or I could just plug it back in, and remain in blissful ignorance of its function.

I now know more than I ever wanted to about those relays. Unfortunately, the fan still doesn’t work. But that is entirely my own fault, down to my electric fan conversion. Much as I would like to, I can’t blame Lucas for that.

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