Club 80-90 Forums

The 40 amp relay number 1 in black box in engine bay has failed. It does not click when 12v is put on 87 and 30. Opened it up and can't find anything suspicious. So l guess it has come to its sell by date.

This is for inlet manifold heater, carb cutout valve and choke.

Is it safe to place a bit of heavy duty wire in the two corresponding terminals inside black box, turn on ignition (no start) for about ten seconds and check power is getting to all three areas mentioned above?

Regards
Stuart

87 & 30 are the switchy bits, you need to put 12V on 85 & ground 86 to check it. What's the coil resistance, pins 85/86?

Yep. You are right. Misread the small numbers. 85 and 86 fires the relay.

Without an power going through relay OHMs on 85 and 86 is about 81.

Usual format is...

85 is normally control ground,

86 is normally control voltage feed.

although a lot of places flip the functions of 85 and 86.
Between them, 85 and 86 energise the coil that operates the electro-magnetic switch in the relay.
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30 is normally the input voltage feed that will used to power the load.

87 is normally the output to the load - your fan, heater or other power consumer.

87 and 30 can also be flipped either way.
87 and 30 are the terminals of the electromagnetic switch.
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In summary -

85 and 86 are the controlling circuit.

30 and 87 are the switched circuit.

maxstu wrote: ↑01 Mar 2025, 11:09
Without an power going through relay OHMs on 85 and 86 is about 81.

81 ohms is in the right ballpark

Thanks to both for the information.

Tested again today and now the relay does not work whatsoever. Plus my multimeter has gone up the spout, and even on the switched off setting still reads 0.03V on the screen. Had to remove it's battery.
So new relay ordered and will buy another mm.

Cheap meter seem to fail , money no object I would buy a Fluke ( I do have one but my son tends to pinch it ). 

I have one of these at my workshop , does the job and has lasted a couple of years. 

https://www.amazon.co.uk/dp/B071JL6LLL? ... n_title_13

 

Thanks for the information TT.
That seems ideal. But may buy one with tachometer RPM reading too