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Bosch ignition relay question

2345 Views 10 Replies 7 Participants Last post by donniefos41, Aug 21, 2021

Mayapaso

Discussion Starter · Mar 29, 2020

I bought this Bosch relay to replace the 20 year old original ignition relay on my 2000 ST4. Nothing wrong with the original but I wanted to refresh the unit. I used the Bosch part number from an old post on this forum. Fitted it today and nothing....dead. Pulled it, replaced with the original yellow which works fine. Put the new unit back, again nothing, pulled it and nearly burned my finger from one of the connectors, I think it was the vertical one marked '30'. VERY hot. What gives; is it a faulty unit or the wrong unit?

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Sheff928

· #2 · Mar 29, 2020

I think it's a different relay; the original is 12v/40a and your new one is 12v/30a.
Use an online checker to verify compatibility; the circuitry may be different between the two.

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belter

· #3 · Mar 29, 2020

"should" be the same. could be a dud.

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Mayapaso

Discussion Starter · #4 · Mar 30, 2020

Thanks guys. I've double checked; the Bosch part number appears to be correct despite it being 12v/30a and the original on my bike being 12v/40a. Mystery? I'm visiting the Bosch dealer tomorrow to ask him to check the new one in case it's a dud.

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Johnny

· #5 · Mar 30, 2020

I doubt either would be switching 30 or 40 amp. The only thing of that size is the starter solenoid

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SS904

· #6 · Mar 30, 2020

Could just be bad. You can check the numbers corresponding to each pin on the bottoms of the relays to see that they are the same. 85 and 86 are for the coil. 87 and 30 are for the normally open contacts.

You should try to get a 40 amp rated relay to replace the 40 amp relay you have. I doubt there are many times you are pulling full current, but if you are, it's going through that relay. The 30 amp was fine for the older bikes with single phase generators. The newer bikes with 3 phase generators are capable of higher current loads. Everything goes through that relay to the fuse box except power to the starter motor.

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Mayapaso

Discussion Starter · #7 · Mar 31, 2020

SS904 said:
Could just be bad. You can check the numbers corresponding to each pin on the bottoms of the relays to see that they are the same. 85 and 86 are for the coil. 87 and 30 are for the normally open contacts.

You should try to get a 40 amp rated relay to replace the 40 amp relay you have. I doubt there are many times you are pulling full current, but if you are, it's going through that relay. The 30 amp was fine for the older bikes with single phase generators. The newer bikes with 3 phase generators are capable of higher current loads. Everything goes through that relay to the fuse box except power to the starter motor.

Thanks for that. The pin numbers all match up.

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Mayapaso

Discussion Starter · #8 · Mar 31, 2020

Sorted. A couple of light taps and it unstuck itself. Should have thought of that before I posted. Move along, nothing to see here.....

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socalnative

· #9 · Apr 1, 2020

If that's a mechanical relay, I'm not familiar with that specific relay, it will probably do that again. There was a physical reason it was stuck. You just dislodged it temporarily. I wouldn't trust it long term. Especially if you didn't ride that motorcycle often.

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donniefos41

· #10 · Aug 21, 2021

There s a guy on Ebay selling the O.E. 40 A relay, type in the search bar the Ducati number for the ignition relay.

Ducati 1991 28740141A BMW 5-series car Ferrari 308 lites main power relay 020308

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donniefos41

· #11 · Aug 21, 2021

donniefos41 said:
There s a guy on Ebay selling the O.E. 40 A relay, type in the search bar the Ducati number for the ignition relay.

Ducati 1991 28740141A BMW 5-series car Ferrari 308 lites main power relay 020308

donniefos41 said:

There s a guy on Ebay selling the O.E. 40 A relay, type in the search bar the Ducati number for the ignition relay.

Ducati 1991 28740141A BMW 5-series car Ferrari 308 lites main power relay 020308

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donniefos41 said:
There s a guy on Ebay selling the O.E. 40 A relay, type in the search bar the Ducati number for the ignition relay.

Ducati 1991 28740141A BMW 5-series car Ferrari 308 lites main power relay 020308

$12.79 shipped.

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