Replacing old/bad relays, most use the standard Bosch 12V 30A 5 spade relay.
But there are two Lucas timer relays, a white one for the seat heater, and a yellow one for (?), that are bad. They both have 4 terminals, 1,2,3,4.
I assume any timer relay with about 10 minutes will work? Or not?
Thanks!
http://www.jagrepair.com//images/Electrical/Elect-Tech%20All2/89%20XJS%20Electrical.pdf
If the pin-out and functionality are the same then it should work. However some delay relays are dependent on the load that they are switching. The interior light delay on my 1992 car is progressive, slowly dimming the lights at the end of the waiting period. When I switched to LED lights the delay period got shorter and was a sudden cutoff instead of a slow fade. Not sure about the different colours, the delay relay for the radio antenna is green - different delay times?
Yellow timer relay is for the rear heated window.
I have one, untested, but can send it to you for the shipping cost.
The aftermarket timer relays have the four spades in the right place, but I can’t verify that each spade is providing the same function. Since they are about the same price as finding a new one specifically for our XJS (about $40), I’ll probably go ahead and buy a new Lucas one.
Thanks for the offer, but I’m putting this off until fall, as I don’t need the defroster over the next several months, and want to make sure I get a working one.
The seat heater timer relays, I verified one of mine works, but the other doesn’t. But i tested out both circuits, and although they work, the actual seat heater doesn’t. So that’s another winter job that I don’t need to fix right now during summer 
While i’m on the subject of timers, I think my 45 second timer relay is caput.
I’m slowly getting my extra air valve system working again, as I want to eventually put back my A/C one day. And I like the idea of a slightly higher idle rev when the engine is cold. (My AAV works fine, and I’ve removed the ability for the system to retard the timing during those 45 seconds)
The 45 second timer is an odd looking relay, I have no idea where/if to buy a new one.
Or could I splice the wires into a normal relay socket and use an aftermarket timer??? I know there’s not much written about this because most people simply disable the 45 second system (which is what I’m currently doing)
Yes you can, but it it must have a positive trigger as it gets it’s signal from the ignition switch to the starter relay. I have found this on fleebay and it’s also adjustable.
I too like the idea of a slightly higher idle rev when the engine is cold, (my AAV valve has a 50° thermostat so when cold there isn’t too much of a boost) so I added a extra air valve (used a spare XJ fuel switch valve) controlled by a thermostat via a relay.
I also hated how the idle drops when you put the car in gear, so I used this valve, controlled by the gear inhibitor switch and an other relay, to boost the idle when in D.
Works fabulously and now the idle is the same regardless if you are in gear or not.
You could retrofit a aftermarket timer relay, it’s just four connections, or even put a normal relay in there, but you will loose the timer function.
Hi Greg,
45sec. timers are available new on ebay:
https://www.ebay.co.uk/itm/232262191932
I’m not sure if seller is offering shipping to US but I could help you with that if you need it.
I bought a new 45 second timer from Martin Roby in the UK; brand new part. Did not work out of the box although all vehicle connections are correct and can jump connector and idle increases. Need to remember these parts are going on 30 years old and capacitors can fail from age. Just don’t pay too much or be too disappointed with result.
Follow up…finally got around to testing my extra air valve (I had bought a new one to replace failing original).
About 65F this morning, engine cold, idles w/o it at 900RPM. (My AAV is working fine) Applied 12V to valve, RPM went up to 1100RPM. I do like that. Hopefully it won’t go up too much when starting from a warm start. After disconnecting 12V from valve, I noticed it took about 10-15 seconds for the engine to slow back down to 900RPM. But going up to 1100RPM was instant.
I also bought an aftermarket timer relay with socket, so will wire that up soon and see how it works. I like that I can adjust it, i may go for just 30 seconds.
Just need to find out what are the four leads to the original 45 second timer.
Black, White, Grey Pink.
Broke out the voltmeter, Black is definitely ground. Grey looks to be 12V Out (to extra air valve). But both white and pink wires showed 12V when I turned ignition on, and then went out after 3 seconds (when fuel pump prime stops). So I guess there are only two possibilities for white and pink, regarding which one is 12V ignition and which is 12V trigger, so I’ll try them both and see which one works.
If anyone is interested, I decided to ditch extra air valve. After verifying relay was working, I bench tested my old and new valves. Turns out, with 12V they fully open, but with 0V, they don’t fully close and can only hold 5inHg. Anything higher gets through. So they’re always allowing a bit of air thru.
I verified, 45 second relay ON provided full intake. When it turned off, the valve had a trickle of air intake.
I don’t need some weird valve giving me a minor vacuum leak that may not be constant.
I used a Toyota valve on my '83. It had an adjuster on it so you could set the amount of boost. Worked great.
Yes, I will reread that part in your book, may do that one day.
My timers were long gone, of course. The only thing I used that valve for was boosting the idle when the A/C compressor engaged.
