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 Topic: relay for water pump power
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deangtp
Joined: January 19, 2012
Location:
Missouri,
United States
Posts: 4 |
| Posted: January 19, 2012 at 7:06 PM - IP Logged |
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I have a 5 pin Relay I want to use to setup power for a bosch water pump for an intercooler. I want it to trigger from the fuel pump, but that's all I know. I am confused which wire needs to connect to what. Anyone wanna help out a new guy?
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i am an idiot
Joined: September 21, 2006
Location:
Louisiana,
United States
Posts: 10,454 |
| Posted: January 19, 2012 at 7:16 PM - IP Logged |
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| Ground terminal 85. Fuel Pump positive wire to terminal 86. Fused power to terminal 30. 87 will power your water pump. |
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deangtp
Joined: January 19, 2012
Location:
Missouri,
United States
Posts: 4 |
| Posted: January 19, 2012 at 7:29 PM - IP Logged |
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85 grounds to battery?
86 gets 12 volts signal from fuel pump wire
30 get power from battery with in line fuse
87 goes to pump
what does 87a do? nothing just cap the wire?
And the water pump has a pigtail with positive and negative wires. Just ground the ground to the body then as well?
Just trying to fully understand
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i am an idiot
Joined: September 21, 2006
Location:
Louisiana,
United States
Posts: 10,454 |
| Posted: January 19, 2012 at 7:43 PM - IP Logged |
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| 85 to the ground terminal of the battery, or to the chassis of the vehicle. 87A is not used in this application. Ground the water pump to the battery or to the chassis of the vehicle. It does not matter. |
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oldspark
Joined: November 03, 2008
Location:
Australia
Posts: 2,856 |
| Posted: January 20, 2012 at 1:39 AM - IP Logged |
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87A is the other contact that is "normally on". (SPDT, or "change over" contacts.)
It will be +12V (connected to #30) when the relay is of (ie - not energised by the fuel pump).
Hence best to insulate it if there is risk of shorting to chassis/body/ground. But it could be used if the relay fails and doesn't switch over (very unlikely) - the move the 87 water pump wire to 87A - but DISCONNECT IT when you do not want the pump running.
[ Another way to guard against shorting is simply to reverse the fused +12V power and waterpump wires (ie, 87 to +12V, 30 to the pump). Hence 87A is connected to the pump (ie, no voltage) else not connected to anything when the pump (30) is switched to 87 (+12V). In that case, upon relay failure (assuming the 30 to 87A contacts & connection is ok), move +12V from 87 to 87A. ]
BTW - why not use the vehicle's water pump? Or is this a separate (coolant) supply? |
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deangtp
Joined: January 19, 2012
Location:
Missouri,
United States
Posts: 4 |
| Posted: January 20, 2012 at 5:05 PM - IP Logged |
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| Separate systems. The engine water/coolant is 180-200*. This is for an intercooler that sits below the supercharger to cool the incoming air charge. You want that as cool as possible and it only needs to run when the car is running. Thanks for the guidance guys. Really appreciate it. |
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offroadzj
Joined: June 03, 2005
Location:
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Posts: 1,240 |
| Posted: January 24, 2012 at 6:51 PM - IP Logged |
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If it only needs to be on with ignition then I wouldn't suggest running it off the fuel pump. You can simply run it off any ignition source (ie radio, cigarette lighter, etc). By running it off your fuel pump you are creating the possibility of being stranded if something shorts out and kills your fuel pump fuse, or the pump itself. Pick a circuit that is not crucial to the running of the vehicle so you can always get home.
Just my .02
___________________________________
Kenny
Former Installation Manager
Circuit City Roadshop
Store #3160
Albany, NY 12205 |
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oldspark
Joined: November 03, 2008
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Australia
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| Posted: January 25, 2012 at 8:53 PM - IP Logged |
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Though IMO that is a consideration - and not incorrect - it should not be a practical concern given normal proper wiring practices and a relay.
A relay should be of negligible load, and its wiring secure. (Its coil could even be fused if it is such a concern.) But the chances of the relay coil causing the controlling circuit's (fuel-pump's) failure is remote.
But as offroadzj wrote... IF "it only needs to be on with ignition...", then use the ignition.
But if the (water) pump is only to be on when the engine is running, then the fuel-pump or similar circuit is desired.
In the old carby days, fuel pumps were controlled by the alternator as was some other equipment like chokes, fuel cutoffs, battery isolators etc. (IE - its charge-light circuit energised a relay that powered such loads.)
With EFI came ECU controlled fuel pumps (or in some cases, (ignition) pulse sensing relays etc).
In whatever case, the added relay should be powered from the fuel-pump's relay output UNLESS its controlling (coil driver's) capability is known.
And only if the engine can run on after the fuel pump relay de-energises (carby bowls, surge tanks) but the water pump is still required should perhaps the IGN be considered (or another other source chosen - eg, alternator charge light). [ But keep in mind, despite people worrying about engine coolant heating up after the engine stops, the heat critical engine parts (head gasket etc) are cooling down! If otherwise critical, electrical engine water pumps are used - not mere fan extensions.] |
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offroadzj
Joined: June 03, 2005
Location:
New York,
United States
Posts: 1,240 |
| Posted: January 25, 2012 at 8:59 PM - IP Logged |
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I agree that the chances of it happening are slim, but you never know when a wire may get pinched... even if you were extremely careful. Its entirely possible to miss something and have a wire short out... and on the slim case that did happen I would rather lose my radio for a bit than be stranded on the side of the road or worse have the car completely cut out in traffic.
However if you need it to work with the engine running (and not just with ignition) then stick with the fuel pump.
___________________________________
Kenny
Former Installation Manager
Circuit City Roadshop
Store #3160
Albany, NY 12205 |
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deangtp
Joined: January 19, 2012
Location:
Missouri,
United States
Posts: 4 |
| Posted: January 28, 2012 at 12:36 PM - IP Logged |
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| The only reason I asked about the fuel pump is that is what is normally used and suggested by other Intercooler users. What size fuse should I use for the 40/30A relay. The pump pulls 2.5 amps continuous. The wire routing will be carefully thought out and protected by convaluted tubing. Bought new Battery terminals to clean up the install. |
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