Cooling System Fan/Pump Control

[91 XR7]

As the title states, looking at controlling the cooling fans and circulation pump in a certain manor. Now this may be long winded for something simply simple, but more info the better?

ECU outputs are for Radiator Fan 1 and 2, Both Negative switched, At the front of the car there are four relays with their terminal 86 going to ignition power, And terminal 85 heading back to the ECU (Rear engine, Front Radiator)
Three relays control the cooling fans in a Series / Parallel arrangement, The last relay controls the Circulation pump.

Now onto what I would like to see happen, the cooling fans staying in the Series / Parallel arrangement, but i would like to see the Coolant pump turn on with the low speed (series) fan trigger, But like to see it shutting off @10-20 seconds or so after the Low Speed trigger is shut off. Most simple circuits i see usually used a positive trigger, but since I'm dealing with a Negative trigger what is evolved in getting this to workout for me?

Now in my dream world, I would have it so that the Cooling fans will run on low (series) and the Coolant pump still on for awhile when the car is shut off only if the high speed fan was triggered when the car was shut off for another 10-20 seconds.

Thank you

 

[91 XR7]

So no one has any insight to this issue?

 

[alec_t]

something simply simple

If it were, I think you or someone else would have come up with a solution by now .
Can you post a schematic of your present set-up?

 

[91 XR7]

If it were, I think you or someone else would have come up with a solution by now .
Can you post a schematic of your present set-up?

Well I can understand that I can't figure it out, since even thou electronics intrigue me, I don't have the knowledge to put forth and make things work!

Also unless you want a scanned copy of a hand drawn schematic, I can just say I'm trying to trigger (?) the following circuit via a negitive trigger.

Click here for now?

Now, with some research I've done on my other topic, seems like I am be able to use a PNP transistor as A "high side" switch? Which in turn can turn on the above circuit on Bowden's site. But by going by sparkfuns site on transistors;

"For example, this circuit wouldn’t work if you were trying to use a 5V-operating Arduino to switch on a 12V motor. In that case it’d be impossible to turn the switch off because VB would always be less than VE."

But is this the case when it's not really a motor it's turning on? Where it's just charging a capacitor?
Now add in the pull up to "shut off" the transistor, does it have to be a 5V source, or can it still be a 12-15V source but just use a large value resistor?

Thank you

 

[alec_t]

What is the voltage of your 'negative trigger' source when not triggered? Are you providing the trigger directly from the low-side switch of the fans, or from a MCU? If the latter, then a 5V source may be needed.
Are the ECU outputs which provide the low-side switching PWM-driven (i.e rapid pulses not steady DC)?

 

[91 XR7]

What is the voltage of your 'negative trigger' source when not triggered? Are you providing the trigger directly from the low-side switch of the fans, or from a MCU? If the latter, then a 5V source may be needed.
Are the ECU outputs which provide the low-side switching PWM-driven (i.e rapid pulses not steady DC)?

Well going by the I/O aspect of the ECU outputs;

Radiator fan relay 1 control B136 18
ON: 0.5 or less
OFF: 12 — 14
—
Radiator fan relay 2 control B136 29
ON: 0.5 or less
OFF: 12 — 14

But it doesn't state if thats with or without the ECU connectors connected, So that Off voltage could very well beign coming back from the Relay itself, since as i stated in the orginal post the other half of the coil is Ignition Positive (12-14Volts),

the switching on the ECU side is either on or off, since they control relays.

I will try to draw up a schematic when i get home

Thank you again

 

[alec_t]

Looks like the ECU output is an open collector/drain arrangement.
I think something based on this will do what you want. The relay is switched by a FET, which has an extremely high input resistance, enabling a long off-delay with only modest capacitor values. This delay is adjustable up to about 33 sec with the components shown :

 

[91 XR7]

Looks like the ECU output is an open collector/drain arrangement.
I think something based on this will do what you want. The relay is switched by a FET, which has an extremely high input resistance, enabling a long off-delay with only modest capacitor values. This delay is adjustable up to about 33 sec with the components shown :
View attachment 87918

The ECU output could very well be that.

And with your Schematic the "in" with the comment (0-15V) underneath is just a ground (low?) input? Since this Schematic seems more complicated then the one on Bowdens site, is this one better?

 

[alec_t]

The 'In' is the negative-trigger input point, assumed to be the ECU output for switching the Low-speed fan.
Bowden's circuit doesn't have the negative trigger that you want.

 

[91 XR7]

Alec_T tried making your circuit, but could not get it to work on my breadboard and trying to simulate (negative) the ECU triggering it.

Right now my bread board is populated with modified delayed on and delayed off circuits on Bowden's site, I'm just using a relay to convert the negative signal to a positive one at this time .

**broken link removed**
Now My question is, Refer to first post in this thread on setup, Would be okay to have the diodes for the relays in the back on the same circuit board as the rest using the ignition there (which is tied to the ignition in the front at the relays) or does it have to be at the relays itself?

Also for the Delayed off circuit, i copied the delayed on circuit abit since with just the BC140 (was given those instead of the 2n3053) The relay wouldn't turn on, but adding the 2n3904 allowed it to turn on like it did with the delayed on circuit. And is there a Single Darlington Transistor that would be a good replacement to the 2n3094/BC140 combination to just simplify the circuit that little bit more?

Thank You