voltage regulator / electronic cooling fan

[Grahmo]

Hi – I am an electronic engineer by trade and for a little home project I put together a little digital gauge that shows battery voltage, engine temperature, rpm. Eventually I will add a beeper for the indicators (to stop me leaving them on) and a warning buzzer when the lights are left on (for the same reason).

So far my gauge has revealed two problems, my voltage regulator was overcharging my battery (the voltage was going above 16V and staying there!) and the engine never really warms up above 70oC when running despite the 88oC thermostat.

Anyway my question – I had a spare voltage regulator unit and have put this in. I am finding the battery voltage steadily climbs to around 15.8V and then charging is turned off until the voltage falls to 12V or so. This happens over a 10 second cycle. From my memory this is how the Lucas unit works, however the ‘switch off’ voltage seems very high. From what I know about batteries they send to boil the electrolyte when the voltage exceeds around 13.8V and should never be charged above 14.4V. Is my spare voltage regulator working correctly?

I know regulator units are very difficult to adjust (you turn one screw and they have a habit of not working at all) so should I just leave it alone? Should I fork out for a new unit? Or should go crazy and design a nice new electronic regulator, doing the same job but using power transistors and precise voltage references to adjust the dynamo’s field current several times a second – not an easy thing to design correctly considering the original unit has probably been working faultlessly for 40 years!

My second question is related to my engine temperature. I know the moggy is over cooled and I have always considered getting rid of the fan blades. When running at tick-over (when you need the fan) there the blades are hardly moving but when on the motorway the fan is running very fast even though there is loads of air moving over the radiator! I figure an electric fan is a much better solution.

Ideally I would like to put the fan behind the grill (in front of the rad.) I have seen this done before. Does anyone know where I can get a nice thin cooling fan? And does anyone know how much bhp the existing fan set up actually uses (I am guessing it takes about 3bhp from the engine). Finally is it just my thermostat isn’t working correctly? I would have thought it shouldn’t open until the water temp reaches 88oC, so the coolant in the engine shouldn’t really be falling below this number.

I look forward to any responses. B.t.w. is anyone interested in my digital gauge? I can layout a proper circuit board so others can build their own unit, if necessary through my company I could probably supply a full kit of parts or even finished uncased units – pm me!

You can find a picture of my project here:
http://homepage.ntlworld.com/grahmo/digidash.jpg

Graham

[MoggyTech]

The old type regulators aren't exactly accurate, so one option worth looking at, is changing to an alternator. A new regulator may help things, but I have seen new ones that are a mile out of adjustment and need setting up.

WRT engine temperature, 70c is about right even with a 88 thermostat. Jonathon at JLH will probably have the best information about electric fans.

Love the electronic readout, I assume this is running from an electronic regulator for it's supply?

You should be able to 'trim' the old style regulator for a better charge min/max range. Adjustments need to be done quickly though, before the shunt coil heats up (30 Seconds) after starting the engine.

[alex_holden]

WRT engine temperature, 70c is about right even with a 88 thermostat.

Mine runs at a steady 90, measured at the cylinder head fitting below the thermostat.

[Grahmo]

Thanks MoggyTech, a quick adjustment to the regulator might be worth a go. The main reason I don't want to change to an alternator is basically I want to keep as many original features of the car as possible whilst keeping it as a daily driver. Obviously things like heated windscreens (which would definately require an alternator) would be nice but for the moment a dynamo and some mist repellent on the windows works fine.

Oh and yes the gauge has its own accurate voltage regulator, definately a must after seeing how much the battery voltage varies!

[bmcecosse]

I've never seen a regulator work as you describe - either there's something wrong with it, or it's connected up wrongly! The voltage steps when charging should be imperceptible - yes it has a 'pull in voltage' as the engine revs up, and a 'drop out' voltage as the revs fall back to idle - but as long as it is 'in' it should control smoothly ~ 14 volts - no higher. Are you sure your voltage readings are correct - and are you taking them directly from the battery terminals ?
Engine temperature - the thermostat should work and hold 88 degrees in the cylinder head. Some heat may be lost down the little 'bypass' hose - and the heater may be taking away a chunk of heat. But when driven hard it should reach the thermostat setting quite quickly! Where are you taking the measurement - and how have you calibrated the gauge ?
Fan - as long as you don't do much idling in traffic - it's fine without a fan - certainly in winter - but a good working gauge will be essential so you can keep an eye on it - and switch off if it's getting too hot in traffic jams! Many modern cars have slim electric fans - look in your local scarppie - or on ebay. Many on there! New electric fans are expensive - so consider what the pay-back time is likely to be. The fan only takes at worst about 0.5 bhp. The fan belt won't handle much more than 1 bhp, and it's got the generator and the water pump to handle as well as the fan !

[MarkyB]

Nice project, I'd be interested in the circuit board.
Will you be making the switch for the fan electronic too?
I've heard of fuel economy meters based on counting the amount the pump is pumping. If you could measure how much ground was being covered too it could be an MPG gauge.

[Roni]

I found an A/C cooling fan off a Mazda that fitted between the grill and radiator, after a little surgery. It is run off a thermostat switch. One thing I noticed with this is that it hardly ever needs to turn on, it is only when stuck stationary in traffic. Any foward movement is enough cooling air to do the job instead. The std radiator was a bit over capacitied. A side effect is that the engine bay is a quieter place now and it is a bit less nerve wracking using a timing light with the fan out of the way.<br><br>

[RogerRust]

I don't think this should be regarded as an advert

I've just bought a very nice Revotec fan for the MGB it fits behind the radiator and sucks air. Its a very neat kit with purpose made brackets. I did ask the vendor if they made them for Minors and he replied that they would if there was enough interest.

[alex_holden]

Electric fans are a very common modification in the Land Rover world. Eliminating the noisy, power-sapping mechanical fan has several advantages. I'm not sure why they aren't more popular on Minors. You would probably want a heavy duty alternator too though because they pull a lot of power and tend to only come on when you're idling for long periods in a traffic jam.

[Grahmo]

Thanks Roni that's exactly what I am looking for! I think another trip to the scrappy is in order. I don't suppose you remember which Mazda the fan came from? I particularly like the way the motor isn't taking up too much of the dimensions of the fan allowing of reasonable air flow when its not running (unlike the huge vauxhall fan I had lying about my garage).

I like MarkyB's idea about looking at the signals for the fuel pump to give approximate mpg. I hadn't thought of that - I wonder how I would convert pump-clicks to pints?

I think my battery has been cooked by the old regulator, and its internal resistance is high, so when its charging the voltage rises/falls faster than is should. (I get the same readings using an old avo style meter). It still starts the car and I've got the starting handle for that cold morning, late for work when it eventually gives up the ghost. I think a fan will draw about 7Amps, which is about the same as the headlights so hopefully the dynamo will hold up - but yes this could be a problem idling night, its a good thing I can keep an eye on the battery voltage now : )

As for the thermostat, I am tempted to try running with no fan blades for a couple of days and keep an eye on the engine temperature (keeping out of traffic jams). This way I'll soon know if the thermostat is stuck open or is working correctly. I'll add a relay to circuit to turn the fan on/off when I get one. Say on at 92 and off at 85oC or something. The good thing is I'll be able to set the levels to anything I want, rather than rely on a bi-metallic switch.

Graham

[alex_holden]

I think a fan will draw about 7Amps, which is about the same as the headlights so hopefully the dynamo will hold up - but yes this could be a problem idling night, its a good thing I can keep an eye on the battery voltage now : )

I think the one I had on the Landy was more like 20A, and remember you get practically no output from a dynamo when idling. Revving the engine up to power the fan when you're overheating in a traffic jam seems a bit counter-productive.

[Grahmo]

I have just tried the vauxhall fan (off an old astra 2.0i GTE) and its drawing 10Amps. So if I go ahead with this I am going to have to be careful to get a small efficient fan. Certainly, anything bigger than 10Amps won't work. I am not sure how much current the dynamo can deliver but lights and a fan may be a problem. I do have an alternator (from the astra) but want to keep the original dynamo if at all possible. Hmm.

Mind you one way of thinking about it is the starter motor draws 30Amps and is used once per trip. So if the fan really doesn't come on that often (say 20sec per journey), then maybe it'll work - of course a larger battery would be a good idea.

[Alec]

Hello Grahamo,

"the starter motor draws 30Amps".

I think you will find it is a lot more, which is the reason for the heavy cable.

I also have an electric fan on my car (Triumph not Morris) and even in summer it rarely comes on. A fan is only required when the forward motion of the car is very slow or stopped. The Morris Minor radiator does seem to be over sized so try blanking a portion of it of to increase the running temperature.
Regarding battery charging voltage, my 17 acr Lucas alternator is designed to charge at up to 14.7 volts.

Alec

[IslipMinor]

I have fitted a Spal 9" (225mm) 'blowing' fan to replace the original 2-bladed fan, which is thin enough to fit between the grille and radiator and is mounted on to the front of the radiator with a standard Spal pin kit. It is the high output version of the 225mm fan, and the reference number for the fan is 3010.0454 and the pin kit is 3013.0013. It draws 7A, and of course this is mainly in traffic at low speeds, so I would suggest an alternator is fitted as well (much better voltage control into the bargain!).

Total cost 7 years ago was £50 including postage and VAT.

I have fitted a thermostatic switch into the header tank and the combination keeps the engine at the design temperature in everything experienced so far, including passes very high up in the Alps (8,000ft plus), the hottest day in the UK on record (100°F) stationary in traffic on the M25 by Heathrow and crawling along at about 1mph for 3 hours or so in this year's Lord Mayor's Show parade.

The quoted 'stat' temperature is 'fully open', so I would expect the 'normal' running temperature to be from about 10° less than the thermostat temperature, up to the stat temperature, depending on weather, use of heater, road speed etc. Outside this range I would start to look at the cooling system setup and condition!!

[PSL184]

I'd like one of those digital dash readouts set inside the case of a rev counter with the rev counter part still working... any chance ?

[linearaudio]

Starter motor would be drawing nearer to 300 amps!! However it seems unlikely you will need to worry about the fan cutting in much, certainly not this time of year. The fan current would be directly related to its power (obvious statement) What I mean is a fan from a Land Rover is likely to be massively over powered. I have a sweet little fan from a Fiat Uno which I collected like you did with your Vauxhall one. Being a similar engine size ie not 2 litreish is probably the sort of thing you should aim at, especially if you are keeping the dynamo.

[alanworland]

I installed my old Kenlowe fan from my old Triumph after changing the blade to a 10in (I think)
Only just got it in between the grille and the rad and the starting handle guide and the bonnet catch, in fact I had to cut the tip off the catch because it would have stopped the fan rotating! Very tight.
But it is great, never comes on except when stationary for long periods when it draws about 12 amps
I also incorporated an overide switch - just in case

[bmcecosse]

Yes - starter motor is a LOT more than 30 amps - maybe even 500 amps 'inrush' on a cold day. The good news is - in winter - when you are likely to have lights etc on, the cooling fan won't be needed. And if you do get stuck in traffic - it's only courteous to switch your headlights off anyway to save them shining in the rear window of the car in front.

[PSL184]

And if you do get stuck in traffic - it's only courteous to switch your headlights off anyway to save them shining in the rear window of the car in front.

Well, when was the last time I saw anyone do that !!!! I wonder though - was it out of courtesy, or were people just giving the dynamo a chance

[alanworland]

Oops - forgot the picture!