Conversion to 12V thermo fan?

[murcod]

Actually, I agree it's a good idea to help improve the A/C efficiency in hot weather. (I'm just not concerned about it causing any damage.)

[murcod]

I've decided it's time to go ahead with this project.

I'm in the process of ordering a Spal dual 11" thermofan with built in shroud
http://www.spal-usa.com/fans/automat...heets/2052.pdf . The shroud measures 596mm x 413mm and going by the specs for JA627 radiator here H52 | DENSO International Australia the core size is 594mm x 475mm, so it will be a good fit.

I'm going to use two of these voltage switches to tap into the standard coolant temp sensor. Jaycar Electronics Voltage Switch One will be used to run both fans in series (for a low fan speed) and then the other will give the fans the full 12v to run full speed.

There's a writeup on how the voltage switch works here: Autospeed

[murcod]

The fan turned up today from the USA .

I've been busy getting the electrical wiring done and have made up the Voltage Switch kit (I'm going to start with only one to switch both fans on full bore, but am doing all the wiring/ relays for dual speed so it can be added later.)

I'm going overboard with all the main wiring and running 85 Amp rated cable for each fan to minimse voltage drops. Even the slightest drop makes a huge difference to the fan speed- I learnt that the hard way in my old 4WD when I converted it.

Tomorrow I need to locate the coolant temp sensor wire at the ECU inside the cabin for working out what constitutes a "normal" running voltage (ie. running temp). I'll then do some monitoring for a couple of days and set my trigger voltage slightly above that level.

I'll also be wiring up the Voltage Switch kit inside the cabin and having a LED mounted inside to indicate when the fans are running. Plus I'm going to install an override switch that can be used if the Voltage Switch fails to switch the fans on manually.

I'm not looking forward to ripping the radiator out for the thermofan install, but I don't see any other way to do it?

[ZX1990]

I'll be interested in the results of this - I know on my 300ZX they haven't found a suitable electric fan that can draw sufficent air thru to avoid overheating - especially in Australia. But at the same time - there is no space for twin fans.... I see that these should flow 2800cfm (approx) I'm not sure about the GV, but I believe the 300ZX clutch fan can flow approx 6000cfm, and you just can't get an electric fan to match that.

Radiator out is probably best, unless you have enough space down the front once the shroud and clutch fan are removed - but its always easier to measure up and make brackets when you have it on a bench in front of you!

Re the voltage switches - you should be able to find the details in the workshop manual - and do a quick calculation to get the normal operating temp.....

[murcod]

Glad to see someone else is interested!

I've got 90% of the electrical side of things done and have been monitoring the ECT sensor output voltage while driving around with the old fan still in. It seems to sit at a norm of around 0.55V when cruising along, the "hottest" I've seen it get to is 0.51V (it's a negative temperature coeffiicent sensor, so starts off at over 2V when cold.)

I've caused a few headaches for myself by using 85 Amp rated cable (very hard to run looms etc.) but I know the end result will be worth it. Under the bonnet is finished including a water resistant relay box to house the three relays I'm using for the dual speed function. I've got a bit of tidying up to do inside the cabin but have got all the necessary power/ grounds/ signal wires run. I ended up running the cable directly to the battery terminals to ensure minimal voltage drop, my new hydraulic electrical crimper came in use for doing the big arse electrical lugs.

I'm well aware of how well the viscous hub fans work and am confident of a decent result using the Spal fans. Bascially the twin 11" fans are exactly the same width and only around 60mm short in height compared to the radiator core. I'm in Adelaide so temps over 42 degrees in Summer do happen. I'd rather have some ECT voltage data for Summer running before I convert it, but worst case I'll just swap everything back over when the weather warms up to get some hot weather data. Currently we've been getting 13 -14 degree days which don't really test out a cooling system.

Mounting the fans will involve some custom steel work, they're quite heavy so using the plastic shroud mounts on the radiator won't be good enough. Luckily there are a few captive nuts and other mounting points I can use located in the general vicinity of the radiator. My Father inlaw is a whip with a MIG welder so it will be relatively easy (I hope!)

[ZX1990]

An alternative to using the stock sender is to pick up an aftermarket gauge for testing (you can get something reasonable for around the $60-$100 mark) and one of the inline adaptors that go into the radiator hose off ebay or similar so you can run it thru to the cabin....although I guess a voltage result is fine - as you know what the stock fan temp ranges are.... it would just depend on how the stock sender is scaled...the 300zx sender and temp gauge aren't worth anything - they have 3 readings, cold (under 65 deg C) the middle (65-105 deg c) and engine is cooked (105+)

And yes - I've used one of those big crimpers, they are worth their weight in gold when you get up to the big cable!

Keep up the good work! Looking forward to some pictures when its done too

[murcod]

The aftermarket sensor might still be happening.

I've come up against a problem with my "Voltage Switch Kit"- the hysteresis won't adjust below 0.2V from what I've found tonight. That's going to cause issues with using the output from the ECU engine coolant temp sensor because I need to get it down to around 0.03V.

What makes me mad is they claim the kit is capable of doing less that 0.02V hysteresis. My guess is it might be because I'm using it to switch on a decreasing voltage instead of the "normal" increasing voltage? There are some component changes between the two that might have affected the minimun hysteresis?

I might have to check out the instrument temp gauge wiring and see what the voltage scale on it is like - a different sensor is used.

[murcod]

An update.

The hysteresis issue with the Voltage Switch Kit has been fixed with some resistor value changes. I've been able to get the hysteresis down to 0.04V which will be just about perfect.

The "normal" voltage range of the ECT (Engine Coolant Temp) sensor is 0.555V to a high of around 0.515V. I'll be starting off with the low speed triggering at around 0.505V and the high speed at around 0.490V .

So that's the electronics and wiring sorted, next will be the actual mounting of the fans onto the radiator. I'll post a couple of pics in the next day or two of the electricals.

[murcod]

Some pics:

Below is a schematic of how it is all hooked up electrically



Part of the design I "borrowed" from a similar set up someone did using twin fans off an Aussie Ford Falcon on a different car.

Next is a pic of the passenger side kick panel. I've installed two LED's to indicate inside when the fans are operating- the green for low speed (both fans in series) and the red for when they're on high speed (in parallel.)

http://users.on.net/~murcod/XL-7/The...20interior.jpg
(the plugs hanging down are where the two Voltage Switch kits plug in.)

Finally, the two Voltage Switch kits assembled and ready to plug in. I've put a manual switch on one to provide a means of over riding the electronics and manually switching the fans onto high speed.

http://users.on.net/~murcod/XL-7/The...20Switches.jpg
(I've used plenty of silicone inside to stop vibration failure of any electronic components that weren't supported.)

There's not much to show under the bonnet at the moment. The three relays in the above schematic have been mounted inside a water resistant box behind the passenger side headlight. It's actually hard to spot any difference because I've loomed all the wiring as per how the factory looms are constructed. It will probably be a couple of weeks before I tackle installing the fans themselves.

The fans look like below:

[ZX1990]

Looks brilliant! I'm going to be really interested in how well it cools once its all done, looks like a really neat job your doing. Like the override switches and LED's too.