Looked at the wiring diagram and notes made when I rewired the '79 coupe.
The fans and pump ( and everything else ) are controlled by an
aftermarket EFI system.
Twin electric fans, each draws 14A at 14.4V.
They are wired thru relays to be in series when the coolant
temperature is below 80deg C. In series they draw 5A at 14.4V.
It is not often they switch to full voltage across each fan.
The coolant pump is a Davies Craig type.
It draws 7.5A at 14.4V.
Below 1200RPM it is switched to be in series with a 0.68ohm 50W resistor.
I never got around to checking the current draw with the resistor in series.
The resistor does not get hot, and the pump delivers enough coolant to
keep the engine comfortable.
Richard Dowling, Melbourne, Australia. 1979 coupe + HE V12 + manual;
1989 convertible; 2003 XJ350.
1 Like
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
2
The coolant pump is a Davies Craig type.
It draws 7.5A at 14.4V.
Below 1200RPM it is switched to be in series with a 0.68ohm 50W resistor.
Interesting. I’d think one of the benefits of having an electric coolant pump is
that it DOESN’T slow down when the engine slows. Of course, I suppose as
long as it’s turning fast enough, perhaps equivalent to 1500 engine speed in
the OEM setup, it’s probably good enough.
I might be a tad nervous about thrashing the car about and then pulling to a
stop to let it idle. I’d want to keep the coolant flow up until it cools down a bit.
Have you considered controlling the coolant pump by coolant temp rather
than engine speed?
does E pump run after engine shut down, for a certain time/temp change!
ron
If the engine is hot after a run on a hot day, I first switch off the engine.
Then turn the ignition back on and the pump runs at low speed.
The fans will also run at low speed unless the EFI detects a high temperature in the coolant, in which case they will be switched to high speed.
Just need to sit in the car a couple of minutes and it will cool down reasonably quickly.
My car is a lump. The donor car, a big old 94 Cadillac Fleetwood Brougham relied on two Efans controlled by the PCM. Alas the fans were too big for then space behind the big 4 row core brass radiator I selected. My son gave me a pair that that just fit. Brand (?) . He thinks they were after market for a mid 90’s Mustang.
the PCM engages them at 95 C. I’m very pleased.
Because of a mishap by me, the cam driven water pump is no longer in place. A Mezzire (sp) electric pump replaced it. Simply wired. On when the engine is running, off when not.
So far just fine,
A bit of after run by each would be neat.
Two other advantages in this arrangement for me.
The original WP was known to drip after a time. The Optilite, (fancy distributot) was just under it and subject to fail because of moisture. Resolved, no WP seal there any longer. And, my car does have a later version of the Optiite with better sealing and a vacuum vent.
The Serpentine belt continues in service to drive the alternator, AC compressor and the power steering pump.
But, if I lose a belt, I can still limp home safely, if not too far, sans PS.