Electric water pump relay

[J-440]

I have the Meziere 300 series electric water pump for a 440 and was wondering if I need some type of relay in the harness. The pump right now is hooked into the fuse block under the hood, which is tied into the fuse box in the car, which is tied into the ignition switch. So when the key is in the run position, naturally the pump will be running. Do I need a type of relay similar to the one that is in an electric fan setup? Thanks again.:thumbsup:

[waynieZ]

Thats a good question I'd be interested in the answer too.

[cees67]

the fan only comes on at high temp setting and kicks off at the same temp setting on the way back down ....if the engine is running that water pump should be running as well. no relay. mine is wired to the ignition as well:thumbsup:

[J-440]

Preciate it 67...ya'll have a good weekend.:thumbsup:

[GregWeld]

A relay is nothing more than a "switchable switch"... it is a switch that can carry a heavy load - switched by a switch that is only capable of carrying a light load. This saves the light switch from burning out.

I would ABSOLUTELY run the electric pump on a relay... regardless of how it's wired now. All you have to do is to wire the "LOAD" (the pump) to the relay and have the relay doing the heavy current... and use the wiring you have now run to it - to switch the relay.

I would think that the pump should be run "continuous". So it might only be switched on once during the run cycle... but should still be on a relay. The wire gauge and relay should be sized correctly for the load. Looking at their website - they sell a 30 amp relay as an "upgrade"...

[J-440]

Greg, so just wire the relay using Meziere's harness between the pump and the fusebox/ignition switch? Would I still need to use the relay even though I'm using a 140 amp alternator as well as the stock voltage regulator? Thanks again.

[GregWeld]

You don't need any special harness.... in order to add a relay to the pump. I'll ASSume you don't understand what a relay does and how to wire one...

The 30 amp relay (should get a nice water proofed version from SPAL) is simply a switch... it gets one leg of 12V HEAVY gauge wire from a battery source - and one heavy gauge 12V GROUND... and on lighter gauge ground - and one lighter gauge 12V switched (ignition). So only 4 simple wires -- the light gauge wires are your control switch. You can choose to switch a relay either by switching the ground wire - or the 12V + wire... they don't care...

The PUMP is either wired with 12V + or 12V ground (-) -- I don't know if it's a two wire install or a one wire and grounded thru the case.

IF --- it's 12V+ wired and grounded via the case -- then that is the LOAD and is connected to the relay via the terminal #87 using heavy gauge wire (I'm using common numbering that is on most all relays) just look at the relay terminal side and each should have numbers next to them.

Connect #86 to your 12V + switched (ignition if thats the switch source)

Connect #85 to ground (any good ground)

Connect #30 using heavy gauge wire (preferably fused as well) direct to battery positive or a suitable heavy 12V+ source

IF your pump has a ground wire -- just use a heavy gauge wire and connect this to a good ground at the block.

Now your ignition switch only has to use about 5 volts and about a half an amp to switch the relay - which will then switch via the heavy wiring - your pump on. So the heavy gauge wiring is doing all the "work" and carrying the load (pump) and your ignition switch and it's lighter duty wiring is only running the relay (a switch) and carrying NO load other than to switch the relay.

This is all a "relay" is --- it doesn't do another thing -- it's just a switchable switch that is in the circuit to carry the work load. They should be used whenever you're going to switch something more than about 10 amps... such as electric fuel pumps - electric fans - high amp headlights etc.