Extended run of coolant pump

[tigerdog]

Here's a crazy idea; would replacing the standard relay with one of these Hella units allow the system to run the coolant pump for an extended period after the car shuts down? Discuss

[Simon_P]

No. Not as a drop in replacement.

What is the logic pump on when what happens etc?

[muley]

I'm confused (no change there!)

What are you trying to achieve?

- always run the pump for a while when you turn off the ignition? or
- Extend the time the pump runs when it is use?
- or something else.


Personally, if the fans are running when I stop and I want to turn off the ignition I wait until the fans stop before turning off the ignition. Normally, it's only a few seconds ~ it did take a little longer here recently because the weather is hot, hot, hot

[Saltire]

No. Not as a drop in replacement.

What is the logic pump on when what happens etc?

Assuming everything is a) standard and b) working correctly now, you’d need to rewire the relay socket to provide the 5 connections needed for the new relay. The standard relay only has 4 connections: 2 for the switching coil, and two for the pump circuit.

[GeoffSmith]

The socket as it stands is missing both an earth and a switched ignition connection.

[Simon_P]

And the logic is wrong.

[tigerdog]

The socket as it stands is missing both an earth and a switched ignition connection.

Well knock me down with a feather. I was going off the wiring diagrams in the v6 Electrical Manual. It shows 5-position relays with similar pinning to the proposed relay. I hadn't pulled the binnacle cover and checked the actual socket.

Screenshot_2021-07-21_15-48-42.png

What is the logic pump on when what happens etc?

As I read the manual's schematic, the logic is that the relay closes when the coil is earthed by the fan temp switch (the lovely brass one on top of the thermostat housing) The drop in replacement would earth the coil as before, but when the switch opens again, would keep the pump running for a set period.

That was my thought anyway. Curses - foiled again... but the stubborn cuss in me wants to open the dashboard lid and see for myself

[Simon_P]

Yes, that's the logic for the pump but you've forgotten the logic for the fans, so you have no supply or earth when you want the fan to run on - That I believe is Geoff's observation.

What is your logic? What do you want to happen under what circumstances?

[tigerdog]

Yes, that's the logic for the pump but you've forgotten the logic for the fans, so you have no supply or earth when you want the fan to run on - That I believe is Geoff's observation.
What is your logic? What do you want to happen under what circumstances?

I think this must be my week to be dense. The logic of the original circuit, as I understand it:

- +12V available through wire N/1B, through the normally-closed side of the fan relay, BN/24C, fuse C4, BR/24F. so +12B is available any time the fan isn't running.
- With ignition off, fan switch grounds, engages coil, relay triggers
- Cooling pump runs until coolant temp drops.
+ Proposed relay would work exactly the same way, except that after the fan switch opens, pump would keep running for a set amount of time.

That's what I thought should happen and how I expected it to happen. What did I miss? Is the issue that the standard Lotus relay has current flowing in opposite directions (L-R for the coil, R-L for the load) where the proposed relay expects 12V to flow (equivalent to) L-R for both sections of the relay? That is, pin 30 supplies +12V to both the low and high current sections, in the same direction?

996152131_02.png

Seems to me, the same relay could also be used in the cooling fan relay position; combined with a momentay switch somewhere south of the diode on BD/24A, it would allow the fan (if ignition on) or pump (if off) to run whenever desired, e.g. sitting in traffic on a hot day, or sitting on the rolling road for a smog test

[GeoffSmith]

To work in extended timer more, the relay needs a hardwired earth connected to pin 31 (as well as supply on pin 30) and the timer is triggered by pulsing pin 15.

If you want the fans/pump to run continuously during the smog test then just short out the a/c pressure switch connector.

[Simon_P]

I understand how the existing circuit works (I think).
I don't understand what you are trying to achieve - I can't think of another way of asking so I'll try again. What is your logic? What do you want to happen under what circumstances?
You are unlikely to get a relay with different pins to work without modification, but you are convinced it will work so why not buy it and try it.

It appears that you want the coolant pump to run on after it has reached the set temperature and would normally switch itself off... For how long, under what circumstances and why? or is it just because! This one has the same pins and an adjustable delay https://www.delcity.net/store/Time-Dela ... 5.h_804416

There are several discussions about fan override switches. If you triggered the pump with an override that may work, or if you want it on every time you could trigger it with the ignition switch or the interior light or...

[Saltire]

Possibly pertinent . . . I’ve fitted a fan (not coolant pump) override with a time delay. I converted an old aircon switch to monetary on/off, and fitted a heated rear window delay module which picks up on the terminal 85 on the cooling fan relay to switch the fans on for 10 minutes. It was very useful in the traffic jam on the A34 yesterday

I would have thought you could wire a similar module for the cooling pump, although you’d need to replicate the fan circuit by using a diode. But I have to say with Simon_P: why would you want to?

[tigerdog]

I understand how the existing circuit works (I think).
I don't understand what you are trying to achieve - I can't think of another way of asking so I'll try again. What is your logic? What do you want to happen under what circumstances?

My logic/desire is pretty simple - run the circulation pump for an extended period after engine shutoff, for the purpose of thoroughly cooling the turbo after a run. With the standard setup, and Smaug's - ahem - unusual turbo, one can hear coolant bubbling for quite a while after shutoff. Bubbling stops while the pump is running, hence the desire to keep it running long enough to drop the turbo's temp.

[tigerdog]

If you want the fans/pump to run continuously during the smog test then just short out the a/c pressure switch connector.

Fekking brilliant! I was going to muck about with a jumper at the relay.

[Simon_P]

If you want the fans/pump to run continuously during the smog test then just short out the a/c pressure switch connector.

Fekking brilliant! I was going to muck about with a jumper at the relay.

or fit a bypass switch. Then you could run the fans or pump whenever it took your fancy.

[tigerdog]

or fit a bypass switch.

That's part of the end-state solution I envision. Bypass switch to run the fans whenever, timer for extended run of pump.

[Simon_P]

A switch and and the relay I mentioned earlier?
You'll want it to play tunes next

[CalElan]

If you want the fans/pump to run continuously during the smog test then just short out the a/c pressure switch connector.

Fekking brilliant! I was going to muck about with a jumper at the relay.

or fit a bypass switch. Then you could run the fans or pump whenever it took your fancy.

I thought I'd read somewhere that the electric pump circulates in the opposite direction to the normal flow.
Makes me wonder if this is true and if so what would happen if you ran the pump when the engine was running!

[Simon_P]

The switch just grounds the relay so the logic is maintained - the fans run with the ignition on and the pump runs with the ignition off.

[tigerdog]

Ended up just plumbing in a switch to run things. Extended run = switch on. Up to operator to switch off