Micro-ISO Relays

My search for micro-relays began with some instructions for converting an ST1300 to an electric windshield. It has a picture of the two types of Micro-ISO relays, as well as the seemingly identical "suspension" mounting sleeves.

Sourcing from Honda

Ron Ayers shows the two-way Micro-ISO relays on their ST1300 cowl microfiche. It's item five, part number 38502-MCS-G00, "RELAY (MICRO ISO 5P)".

For reference, his same relay is available from Cycle-Parts for $6.46. Ron Ayers, by comparison, is $6.15.

Also on this same microfiche page is item four, p/n 38306-MCA-000 "SUSPENSION", which is a sleeve intended to attach the relay to the cowl. These "suspensions" also make excellent waterproofing housings for simple switches, such as you might use for accessories on your motorcycle. Just cut a round hole in the end and fit it snugly around the switch body, and zip-tie the open end closely around the wires. Don't buy this one, though, because...

There is another, seemingly identical relay suspension available. But it's nearly half the price!

• 38306-MCA-000 $6.57
• 38506-MCS-G00 $3.27

This second, cheaper relay suspension appears on the ST1300 wire harness microfiche as item nine. Also shown is item eight, 38501-MCS-G00 "RELAY (MICRO ISO 4P)". This is a four point relay, meaning that it can only close a single circuit, it cannot switch between two circuits. Since it's the same price, at $6.15, I can't see any reason not to buy the five-point relay!

These relays are made by Omron. The five-point relay is Omron part number G8HN-1C4T-RH. The final H indicates "high capacity". The 4T- indicates sealed (unsealed is -2T). -1A indicates SPST ("four-point"), while -1C indicates SPDT ("five-point"). As near as I can tell, the -R indicates a suppression resistor is used (where??).

Omron's GH8N-J Data Sheet has the following specification charts. The relevant information is in bold:

Part Number		Contact Type
Unsealed	Sealed
G8HN-1A2T-RJ/DJ (DC12V/DC24V)	G8HN-1A4T-RJ/DJ (DC12V/DC24V)	SPST Standard
G8HN-1C2T-RJ/DJ (DC12V/DC24V)	G8HN-1C4T-RJ/DJ (DC12V/DC24V)	SPDT Standard
G8HN-1A2T-RH/DH (DC12V)	G8HN-1A4T-RH/DH (DC12V)	SPST High capacity
G8HN-1C2T-RH/DH (DC12V)	G8HN-1C4T-RH/DH (DC12V)	SPDT High capacity

Arrangement			SPST,SPDT
Contact material			Silver tin oxide (cadmium free)
Contact voltage drop	Standard		Less than 200 mV at 20A
	High capacity		Less than 200 mV at 35A
Max. Switching Current	Standard	12VDC	N.O. side: Inrush 100A, Steady 20A N.C. side: Inrush 50A, Steady 10A
		24VDC	N.O. side: Inrush 30A, Steady 10A N.C. side: Inrush 15A, Steady 5A
	High capacity	12VDC	N.O. side : Inrush 120A, Steady 35A N.C. side : Inrush 40A, Steady 20A

Incidentally, the G8HR line seems to be a high-capacity standard ISO relay, handling 70 amps. It uses a pinout like a typical Bosch-type relay, except that the input leg is massive.

Alternative Sources

The Mouser catalog, page 1300 lists the G8HN-1C2T-R-DC12 relay for $4.38. However, these are unsealed (2T-) and not high-capacity (no final H). So: don't use these.