What does this relay do ?

The relay on the left side of this pic (The Black One) has obviously been changed for a different type.Although the car runs well I would like to change it back to the original unit. On pictures I have seen the original looks like the starter relay and is cylindrical in shape. Any help would be apprieciated Thanks

Hi.

That is the ignition relay.

I've attached an image of how the electrical would have originally looked.

The relay is a basic SPST unit, so alternatives could be substituted.

Kelvin.

Many thanks Kelvin !!

I agree with Kelvin. The original on mine would produce random and complete engine failure. It would always start immediately after. Finally traced it down by accident and replaced it with a cheap, square Bosch unit. Like any electro-mechanical device they just wear out mechanically and suffer internal failure.

Using something other than original should not be a problem, but I'm not sure what is installed on yours. I'd worry less about the relay itself than about how it's wired in. A standard auto relay available at your local auto parts or electronics place for a few bucks (see attached photo) would still allow use if the standard connectors. Looks like yours has those cut off and patched with electrical tape to a pre-formed connector / relay pair. If the wires are soldered together under that tape you're probably OK, but if not, it's a stranding ready to happen.

I'd fix properly to the normal blade connectors and use a standard auto relay. Much cheaper than the "original" round one....

Bob

Bob I owe you a large Moose Head beer! My 75 has had a few random engine shut downs last year. It always started right up and ran perfect then out of the blue a week or month later another shut down. I could not figure out what was up with that. Thanks a million for a simple fix. Now if I can just figure out what wire belongs on which prong on the replacement relay.

I often wonder how many starter motors have been changed for want of a cheap and oh so easy to replace relay :S

Look at the pin numbers on the relay. They're the same as the Lucas unit. PnP

I found mine by unfastening the relay from the inner wheel well and while it was running I just rotated the hand I was holding it in. I felt a click and the engine died. Any motion would produce the same result. On the road, right hand turns were the usual culprit. Not all right hand turns would do it, but any time it died it was always a R/H turn.

John
Your 75 also has a fuel Inertia switch, which may have a loose connection. Mine was installed right where I would reach up,to pull the hood release. Many times I would hit one of the 2 wires, and it would fall off. Drive about a quarter mile and suddenly nothing!! Fuel pump would stop, and no gas. If your wires are loose you could be experiencing intermitten shut off. Just my thought.
Ken

Thanks Ken for reminding me about the fuel inertia switch. Actually the 75 is a UK model and it does not come with that fuel cut off switch but my 78 US edition does have that switch and as a matter of fact the wires are somewhat melted to and from that switch. Something I must attend to before this May when we are planning a trip to Italy for the Gabicce Mare by the sea event.

Speaking of the melted fuel inertia switch, I have the same on my 78. Why is this 'switch' here? THe wires running in and out are the same gage so it's not a relay to control heavier current draw. There two on the input side of the switch -one form the ignition and one going some where, on the other side the wire goes to the fuel pump. THe little sign says something about the plunger having to be all the way down for the pump to run. THis some kind of a rollover cut-off switch? THe Manual seems not to refer to this other than showing it in the wiring diagram. Can I just replace the melted wires and connect them all together?

Joe, that's there so that if you should find yourself upside down, the fuel pump will shut off.

These things do happen! I think it also disengages during a hard crash, upside down or not.