Aux. Water Pump Current - PeachParts Mercedes-Benz Forum

bpeters2 · #1 11-22-2011, 11:26 AM

Does anyone know how many amps the auxiliary coolant pump draws. I'm thinking about using it to circulate coolant in conjunction with a tank-style "block" heater (would need to install some sort of switch to provide current to the when car was turned off). If I used it may be running for several hours (without battery charging) and don't want it to drain my battery. Thanks

vstech · #2 11-22-2011, 11:28 AM

under 1 amp...

bpeters2 · #3 11-22-2011, 11:48 AM

Thanks vstech. Does anyone know of some type of solenoid?/switch?/relay?..(preferably cheap) that I could wire up such that when it receives 120v it would "switch on" a 12v DC circuit (power to aux. pump in this case)....I usually hook my block heater up to a timer (the type that just plugs into a wall outlet and then connects to your device) so that it only heats for 3 hours or so in the morning, it would be nice if the aux. pump could be energized only when the heater received current.

vstech · #4 11-22-2011, 11:55 AM

... you could attach a 2amp trickle charge to it... heck, you could also use it to maintain the battery... put an isolation relay in there and have both running when plugged in.

Air&Road · #5 11-22-2011, 01:29 PM

The max for the one on the 124 cars is 1.3Amps and it looks just like the one for a 123. As VS says though, the normal current might be less than an Amp.

bpeters2 · #6 11-22-2011, 01:52 PM

Quote:

Originally Posted by vstech

... you could attach a 2amp trickle charge to it... heck, you could also use it to maintain the battery... put an isolation relay in there and have both running when plugged in.

Can describe what an isolation relay is and why it would be necessary. thanks

vstech · #7 11-22-2011, 04:43 PM

isolation relay takes one portion of the system out of the loop during certain circumstances...
in this case, you would wire the pump to the one side of the ISO, and the battery to the other, then the pump would not run when the car is driving, but it would run when the trickle charger was plugged in, and both the pump, and the battery would benefit from the trickle charger's power output.

bpeters2 · #8 11-22-2011, 04:59 PM

ok I think I undestand. So the wiring would be 120v to charger. Charger connected to battery and then a wire running from the positive battery terminal to the one side of ISO, and other side of ISO wired to pump? S

barry123400 · #9 11-22-2011, 05:34 PM

I am not going to study a schematic but be careful how you go about this. Higher than normal current in that circuit can take out the climate control unit.

This is based on the recomendation that you check the draw before installing a new one. Additional prevention is to install an additional small fuse in that circuit to protect the ccu.

Actually that is a good ideal even on a car without any problems with the ccu. If the small motor ever jams up or burns the windings the fuse will blow rather than the ccu unit as the current draw goes up.

vstech · #10 11-22-2011, 06:35 PM

Quote:

Originally Posted by bpeters2

ok I think I undestand. So the wiring would be 120v to charger. Charger connected to battery and then a wire running from the positive battery terminal to the one side of ISO, and other side of ISO wired to pump? S

close.
I'd wire the 120v to both the block heater, and the TRICKLE charger, have the output from the trickle charger feed the ISO and the battery, then have the output from the ISO feed the pump.

compu_85 · #11 11-22-2011, 07:46 PM

Except that the pump needs to run in "normal" mode too. The current draw is small enough you could use some diodes to isolate the climate control system from the trickle charger / pump.

-J

bpeters2 · #12 11-22-2011, 10:32 PM

Thanks for all the advice. Any advice (or links to applicable products) about where to find the isolation relay and the diode suggested. thanks again.

vstech · #13 11-22-2011, 10:58 PM

hmmm. isolation relays are available at most auto parts stores. in the towing section usually. there is a large selection at most pep boys
the isolation relay could work as the diode situation mentioned above...

the connections I suggested were for a separate pump from the CCU one. I misunderstood what you were asking for.

if you want the existing pump to come on with the block heater, I'd just hook the charger to the battery, and have the iso between the ccu and the direct battery connection to the aux pump.

bpeters2 · #14 12-02-2011, 09:04 AM

Quote:

Originally Posted by vstech

if you want the existing pump to come on with the block heater, I'd just hook the charger to the battery, and have the iso between the ccu and the direct battery connection to the aux pump.

Sorry, I'm still confused. Seems like the relay would have to be between the battery and the pump or else the pump would always be running. In this scenario what would you hook up to the relay to "trigger" the relay to make the connection between the battery and the pump? thanks