why did I ask a stupid question (again) - kenlowe fan/alternator problem.

[snowric]

OK this is why i asked my previously dumb question about earths.

 

I hope i have set out the below clealry enough..

 

I am getting odd symptoms on the start up cycle of my electric kenlowe fan, clicking on start up, relay clicking on and off, finally it dies and car nearly overheated in Sunday traffic.

 

I started with the obvious ones - eg why isn't that earth lead earthed next to thr steering column and what does it do if it doesn't make a difference.

 

Here are the symptoms.

 

1. I am using the kenlowe electronic controller, a 30 amp relay and a 14 inch fan which draws c 25 amps at start up and settles at around 12 amps. I have an allegedly 65amp alternaotr and a bosch fuel pump. So max load = 12 +25 +2 for ignition.

 

2. When car is not running I can use my manual override switch to trip the relay, the fan runs, amps up then drops to steady 12 amp.

 

3. the fan is wired correctly (as tested above) and the unit appears to be wired correctly (otherwise it wouldn't do 2 above) but for detail, specifically - here is how I have done it:

 

a. main power feed for the fan direct to the second plug on my lucas alternator (so its 'below' the ammeter so ammeter reads correctly). Voltage reads 12.6V

b. electronic unit feed, this powers the relay on and the electornics linked to the thermal switch is attached to the ignition side (white) of my fuse box - voltage reads 12.2V on start up with ignition on

c. earth for relays and electronic unit - radiator stay - beeps to zero ohms on my continuity tester to battery earth

d. earth on fan motor - radiator mounting bolt - again beeps to zero on my continuity tester

 

4. before you ask i have replaced the electronic unit with a new one - not cheap and problem not solved. grrrr

 

5. start up car, alternator happily re-charges battery all is good car purrs along nicely in the nice happy way that our cars do when they behave. Lots of smiles/nice looks, general courtesy on the roads (unusual in London) not at me.

 

6. Feeling of general goodness, temperature rises as I sit in traffic

 

7. clicking noise, ammeter, bounces sharply left and right

 

8. looking under bonnet, clicking is coming from fan motor, starting and stopping

 

9. feel the relay in the electronic unit, this is clicking on and off

 

10. check voltage at ignition side of fusebox - this is no longer a steady 13.8V but is now varying up and down wildly with very high transients and zeroes - really wildly +200V ? to zero.

 

11. things settle down, transients drop and fan runs steadily until cycles starts again.

 

I have a newish 65amp alternator and this all worked happily for several weeks.

 

So from doing some reading on alternators but am now stuck - what seems to be happening is that the fan relay cuts in, the fan motor demands lots of current = power, the alternator blasts the current but this is causing some kind of transient spike and the voltage drops to zero, relay closes, alternator field re-builds, power again, repeats until the fan is spinning quickly enough to cope and current demand is lower

 

So my conclusion is that the alternator must be buggered in some way - I just cant see how else a sudden 25 amp draw could cause these king of spikes.

 

Any thoughts gratefully received. Why would I see these kind of spikes - I have been testing the voltage at the ignition circuit as this is what would power the relay closing.

 

Snowy

 

 

 

[brian -r]

Hi snowy

Just found the wiring details for the fan this may solve your problem

 

Red pos supply direct from battery supply , use terminal block next to fuse box

 

Yellow pos to control circuit , switched supply from ignition

 

Green pos from overide switch

 

Orange with fuse holder to fan

 

Black negative to earth for control circuit

 

Black from fan to earth

 

Cheers

Brian

Edited June 3, 2014 by brian -r

[pfenlon]

By the way there are NO stupid questions, only stupid answers.

 

Hope you have it solved now.

[snowric]

Thanks Brian, I have not wired it direct to the battery as this would cause the ammeter to deflect the wrong way when the fan runs. It is effectively wired to the battery via the alternator connection and the brown and white charging lead, so a little further down but in essence a direct connection on a heavy gauge wire. I will try a temporary rig tobnight and see if this calms things down.

 

I am beginning to think it is the voltage regulator on the alternator which is not coping with the sudden demand of the fan and producing high voltage spikes. Appraently this happens on old planes and they have a trip relay that shuts out the alternator to stop the spikes damaging avionics. Of course you then fly on the batteries....

 

I am going to try my old (lower output) alternator tonight that should cope with ignition, pump and fan.

 

Snoyw

[Steves_TR6]

It does sound like an alternator field/regulator or earth issue to me.

[snowric]

I will re-do the earths too.

 

Shame it's a newish alternator from Revington - I will send back to them and ask them to test it.

R

[Mike G]

Hi
You are trying to get the alternator to perform in away it was never designed to operate! Your voltage stabiliser reacts to a falling voltage in your battery, by supplying a higher voltage to the windings of your alternator; this increases the electromagnetic strength of the alternator. This in tern generates more current. As the battery recovers, the voltage output from the stabiliser reduces and the alternator delivers less charge to the battery. Why not wire your fan through a separate fused supply from your battery. This way, your alternator will operate correctly and the power to your fan will not be routed through your ammeter.

Mike

[jerrytr5]

This: " I have not wired it direct to the battery as this would cause the ammeter to deflect the wrong way when the fan runs"

and this: "main power feed for the fan direct to the second plug on my lucas alternator"

don't make sense to me.

You should not be connecting anything direct to the alternator - I think this is the crux of your problem.

As a test, remove the red wire that you have connected to the alternator and connect it direct to the positive battery terminal through a fuse.

Jerry.

[AlanT]

THROUGH A FUSE.

Don't ignore that bit!

[TR 2100]

As someone said above, no stupid questions, just stupid answers.

However, I'll risk it.

Are the fan blades the right way round for a suck or blow operation,

depending on where you have the fan fitted?

I just thought if the blades were the wrong way around, that would

lead to overheating and probably overload the system when driving.

 

AlanR

[snowric]

Thanks guys - it is a blower and it is blowing.

 

The supply is fused both sides (ie before the electronic unit and before the fan motor 25 amps each).

 

My connection to the alternator is as per the Revington aux fuse kit which plugs into the 'spare' alternator feed and provides a fuse box some live some ignition relay switched.

 

I have called them and they think its the alternator behaving oddly and it needs to be returned.

 

I will re-do the earths and test again tonight with my old and trust 37Amp alternator which should puff along but do the job.

 

Snowy

[littlejim]

Can you connect it just via the thermal switch to a connection on the 'draw' side of the ammeter, leaving out the 'electronic controller' to see how it behaves.

If the "alternator happily re-charges battery all is good car purrs along nicely" seems an unlikely suspect.

What is the 'electronic controller ' supposed to do that the 'thermal switch' doesn't?

The Davies-craig one has this set up;

[snowric]

this is basically my circuit. I have a switch s that the green wire can be made live tripping the relay and making the fan run. the electreonic controlle combines the relay and the thermatic switch.

 

I am concluding that one of my diode packs on the alternator isnt working properly and that this isn't relevant when I am running a bosch pump and ignition but is a problem when I double the power output.

 

I will report back if/when i find the answer.

 

Why are electrical gremlins always such a pain ?

[jerrytr5]

 

The supply is fused both sides (ie before the electronic unit and before the fan motor 25 amps each).

 

My connection to the alternator is as per the Revington aux fuse kit which plugs into the 'spare' alternator feed and provides a fuse box some live some ignition relay switched.

 

OK you clearly have some additional wizardry so us guessing is not going to be helpful.

One point though, surely you would only need a large fuse for the fan motor. The electronic gubbins should only require a very small fuse - suggest you verify this.

Oh yes, electrical gremlins are always a pain because it's witchcraft.

Jerry

[snowric]

I agree and will check I have fused the electric supply to the unit - this is what ahs caused the blown unit previously. Good point.

 

R

[McMuttley]

Very keen to know the outcome of this as I (am) was about to hand over the same kit to my man at the garage to install.

[snowric]

Ok I have fitted the old alternator and the symptoms remain. Grrrr

 

More thinking. The voltage across my battery leads when car is ticking over is 14.3V ie v good charging going on.

 

BTW is it normal for me to get very variable voltage readings from the fuse box while the car is running ? Can you get major cross talk from the ignition system and the cars electrics.

 

If so this would be enough to cause the problem as the yellow feed needs to be a constant 12V to allow the thermal switch to open the circuit.

 

I get readings all over the place.

[McMuttley]

Wormhole ?

[Lebro]

Sounds like a can of wormholes !

[Peter Cobbold]

Wormhole ?

Positrons........ maybe.

[littlejim]

"the electreonic controlle combines the relay and the thermatic switch."

 

??The 'thermatic'# switch can't be part of the relay, it has to be in the coolant/water to sense the water temperature. (# the blob at the end of the zigzags on the DCraig picture)

Be interesting to see a diagram of your set up.

[brian -r]

Perhaps your getting a little to technical here D V M s are brilliant for measuring clean supplies , electronics etc

but in my experience tend to ramp up and down on some unclean supplies, TR electrics can not be relied on to be clean or

particularly stable.

 

These new Kenlow controllers are not particularly reliable I`m on my second and know of others who have had trouble

With them on classics.

 

Good luck

 

Brian

[snowric]

Today I ran the earth from the electronic unit back to the earthing point near my fuse box and ran a lead from the battery terminal to the unit via an inline fuse.

 

The unit works with much much less fuss.

 

I switched the live feed back to the ignition circuit and the problem re-curred.

 

My conclusion has to be that the Kenlowe units are sensitive to the voltage on that line and not on the optional manual switched line.

 

I now have to decide if I care that the fan runs on while it is hot. A debate I have seen at length elsewhere.

 

Frankly, as it works maybe i will leave it alone, I can also isolate the battery if I am worried about the state of charge.

 

Thank you all for putting up with my wittering.

 

Time to tidy my engine bay tomorrow.

 

If this fails am going to try the Revotech instead.

 

Snowy

[snowric]

An update.

 

I have fitted an electronic ignition unit to my distributor and a replacement coil. Hall effect type from pertonix, easy to fit.

 

The problem with the fan has disappeared; no clicking, it just kicks in and out with the correct show on the ammeter.

 

The fluctuating voltage I was finding with my multimeter has also disappered/ abated.

 

So it seems that the ignition system (back emf or similar) was causing the problem with the electronics in the kenlowe unit.

 

Thanks for all the suggestions.

 

I am not sure why as the car ran fine beforehand....

 

Mysterious things these TRs and ;lucas electrics...

 

Snowy

[ianc]

Think carefully about allowing the Kenlowe to continue to run after the ignition is turned off.

Yesterday morning at Kop Hill Climb, TS2's battery was flat as a pancake because the fan had been left running and there's no thermostatic switch to turn it off. It took us a while to restore some charge via jump leads and get the engine running.

I think that this winter, TS2's Trustees need to get a thermostatic switch fitted into the metal pipe which returns coolant from the bottom of the radiator to the pump - a very simple 'fix'!

Ian Cornish