relays electric after run water pump

Desperately need help !!

I have a 1986  Audi coupe with a turbo engine.

I want to add an electric water pump, which turns on (during ? ) and after the engine is turned off. It will be activated when the engine is hot and turn off after it has cooled down.  Why ? to help coolt he turbo down after engine is shut down.

I have been told to use two relays one (87,86, 85, 30) the other(87, 87A, 86, 85, 30). This works in part, however the (87,86, 85, 30) relay gets very hot and practically drains my battery overnight. Maybe I'm using the wrong type of relays ? Maybe a relay that remains on for 8-10min. and turns off ?

This is what I have:  12v. electric water pum and a Thermo switch.

What I want to know is how should I wire it uP. What relays other than those below could I use ?

All considerations would be most appreciated.

Miguel Boniface

With the limited information you gave, I would assume you can do this with one relay:

30: 12vdc battery (fused for whatever the water pump recomends)

Wire the other side of the thermo switch to the battery (constant 12vdc)

How much current does the water pump require?  You need to make sure your relay is capable of driving the load.

Kevin,

Thank you for the reply. You're right ... At the risk of not wanting to be complicated, I guess I wasn't very clear. Maybe it would be simpler to put my problem as a question.I f you wanted to wire up an electric water pump so that it came "on" after you removed the engine from the ignition, what would you do ?

You have two items: a 12volt pump with two pins (+ and -).  Your thermoswitch has two pins as well (+ and - ) The thermoswitch will activate the pump when the engine has  been turned "off" and is above a certain temp. (not important for this exercise) and open it as sson as the engine temp. has dropped down again.

I think a 30amp relay will do the job.

Regards,

Miguel

I would still wire like I said in my first post.

Wiring it that way will allow it to come on after the ignition is shut off and the temp is above the thermo switch setpoint.  The way I described would be completely independent of the ignition status.  You 'may' want to put some sort of time dely off on the circuit just to protect the battery incase the switch sticks.

I like switching the Hot. A short is a short and I see no difference in performance.

You see I work on Hot Water Pressure Washers and they always switch the Hot.

As long as the line is properly fused it really doesn't matter.  In a car, it is typically more convenient to switch the (-) because you don't have to run two wires (you can ground the switch at the switch).  However, if you are already working under the hood it really isn't going to save much.