Relay connections

[DanielC]

This is a diagram of the relay connections used on the "Bosch" type relay commonly used on cars, boats, ETC.
Pin 30 normally goes to a power source, through a fuse or circuit breaker.
Pin 87 normally goes to a load of some type. (lights, fuel pumps, engine computers, whatever. Pin 87 connects to pin 30 when power is applied to pin 86, and pin 85 is grounded.
Pin 87A connects to pin 30 when the relay does not have any power applied to the coil
Pin 86 is the coil positive side.
Pin 85 is the coil negitive side.
A lot of times, pin 30 is always hot, even when the key is off, or in the case of my boat, even with all the breakers off.
The coil of these relays is switched on or off on either the "ground" side, or the "hot" side.
Example: on a GT-40 engine in my boat the key applies power to pin 86 of the engine computer relay, and pin 85 is grounded. The key switch controls this relay.
When the engine computer relay is turned on, power is applied to pin 86 of the fuel pump relay, and the computer only grounds pin 85 wnen the computer thinks the fuel pumps should run. The computer switches the ground side of the relay.

[Mikeski]

RE: Relay connections

Is your post just informational?

nice explanation for the operation of a cube relay...

[DanielC]

RE: Relay connections

Yes, just information.
If someone has a question about how these relays are used, I hope this post will help them.
Kind of like my post on checking the fuel pressure, and ignition system functioning that I made.

[mike-d]

RE: Relay connections

Danielc,
your information is greatly appreciated. too bad your on the wrong coast, would need your help locally.

[DanielC]

RE: Relay connections

Whatever coast is the wrong one is a matter of perspective. The boat ramp to the local river is about 12 minutes away, and if it is windy on one part of the river, going around a bend puts me in flat water.
The skiing season can usually be started in mid June, without wet or dry suits, and goes until about the beginning of October. When it is hot here, the humidity is almost always low. We have about two weeks of freezing weather in the winter, and it is a two hour drive to snow skiing. We can snow ski, or board the year around, on Mt Hood.
I like where I live!

[mike-d]

fyi

Danielc,
I think you took my reply wrong,
wrong coast to me is that your on the opposite side of the states, too far to visit and fix my **** boat that wont start!!!! :grin:

Mike
I like the idea of snowboarding in the morning and wakeboarding in the afternoon, and then surf the evening session.

[DanielC]

RE: fyi

Mike, I would love to help you, if you were not on the other coast.
Compression, Ignition, Fuel. Supply all three things, at the right time, in the right ratio, and the engine will run. Millions of engines prove that every day.

[NautiBrophy]

Daniel,
If you have time can you take pictures of the different relays saying which one is which and a decent view of the ngine so I know where they exactly are? Thanks

[DanielC]

Here is a picture of the relay location. Ignore the pen pointing to the underside of the plate the two relays are mounted on.
One of the two relays controls power to the computer, the ignition, and power to the fuel pump relay coil.
The other relay is the fuel pump relay. Both relays are identical. The electrical harness will reach either relay, so I cannot tell you the one on the right (or left) is the fuel pump relay.

[DanielC]

The fuel pump relay will have wires with the following colors:
Blue/Orange
Red/Purple
Green/Yellow
Purple/Black

The computer relay will have wires with the following colors:
Purple
Black
Red/Purple
Purple/Black

Look for the Green/Yellow wire. This is positive to the fuel pumps.