I'm suspicious.How do I tell if its 6 volt?

[nigel bickle]

K. So this 'Starter Motor Specialist' tells me he can supply the 6volt pre engaged solenoid I need for my 50's Renault -when absolutely no one else can.

 

Tells me 7-10 days. A month later, I'm kicking off (politely). Nowt -and very little in the way of comms since I paid.

 

Until he recieves my 'Particulars of Claim' laying out what I'll be asking for from the County Court.

2 days later I receive a new, totally unmarked solenoid in the post- in a small box with all the labels stripped off.

 

Now -it has always been (comparatively) easy to find it, in 12 volt - but this 6 volt has allegedly been made for me..

 

So -before I fit it to the starter motor, then the car (effectively rendering it 2ndhand, and unreturnable) -which is a flamin' awkward job; how do I know if I have the real deal?

 

Are there any checks I can make -to quell my nerves?

[Inspector Morose]

I know this sounds blatantly obvious but try 6v across it? If it is 6v then no harm done with over voltage and if its 12v chances are it won't work/won't sound right (lazy) in operation.

[cobblers]

Do you have a 12v one to compare? measure the resistance, the 6v one should be quite a bit lower.

[nigel bickle]

Ive run 6 & 12 across it -briefly. No discernable difference.

 

Sadly - I havent received the old one back -despite paying extra postage for its return. That is being addressed now -but doesnt help short -term.

[Stixy]

Fit it and if it doesent work its a defective part cant you just return it ?

[nigel bickle]

Thanks -truly helpful.

[DSdriver]

Fit it and if it doesent work its a defective part cant you just return it ?

 

Exactly, as long as you told him what you wanted it for and explained that it must be 6V (which you obviously did), if it doesn't work it was not fit for purpose and you should get a refund.

[nigel bickle]

Perhaps I didnt explain myself clearly.

 

I do NOT want to fit it -unless its right. Its a very difficult motor to put back together (stripping it out took an hour -once on the bench), & the engine bay is bloody awkward to get it back into. It'll take me a clear 3 hours to fit; then a 2 day lie down for my back to recover.

 

Regardless of 6 or 12 -it'll then work for a while; but if its 12 -it'll fry it in a few weeks time.

 

Which then puts me back where I started. Several hours to get it out, prob in inclement weather, then pursuing him for redress (in a much harder situation to prove), the need to find another 6 volt unit & a totally screwed car -again.

 

Seeing as its sitting here- now -is there a test to discern?

[Timewaster]

Do you have another 12v solenoid to hand? I would try that with 6volts and compare it to the new one.

[Rocket88]

My understanding [prob total bollocks] is that a 12v solenoid will work with 6v, but a 6v one will burn out if you stuff 12v through it.

If you have a local auto electrician handy, I'd trot it round to him and ask for some advise. If, as you say, there's no discernable difference in readings, you may have been sent a "parafin re-con" unit.............

[nigel bickle]

Yup -think you're right,sadly.

 

I kinda hoped there would be a way for me to check.

 

I've a bad feeling about this..

[hairymel]

My understanding [prob total bollocks] is that a 12v solenoid will work with 6v, but a 6v one will burn out if you stuff 12v through it.

 

i agree with this.

 

bench test it with 6v and if it pushes hard enough to break your fingers it might well be ok, possibly

[Rocket88]

Just to clarify, I presume it's a "stand alone" solenoid, which you could fit anywhere in the engine buy? If so, and as the consesus seems to be that shoving 6v through a 12v soolenoid is ok, why not fit a 12v one?

[Junkman]

My understanding [prob total bollocks] is that a 12v solenoid will work with 6v, but a 6v one will burn out if you stuff 12v through it.

 

It's exactly the other way around.

 

If you have half the voltage, you need twice the current and the latter is what burns stuff out.

Hence:

 

Fitting a 6V solenoid to a 12V system, or operating a 6V solenoid with 12V, is not that big of a a problem.

Altogether, it is quite unproblematic to convert a 6V system to operate with 12V and it has been done very often with old 6V cars. With this I mean, I did it.

I converted countless 6V Beetles, Trabants and Renault 'trelles to 12V.

 

The other way around is problematic. If you operate a 12V solenoid with 6V, it will draw twice the current it is designed for and quickly burn out.

Hence the question raised in this thread is totally sensible. Only that I don't know the answer. I cannot think of a way testing whether it is a 6V or 12V

solenoid without knowing what the internal resistance should be.

[nigel bickle]

Agreed.

 

Its a pre-engaged unit -bolted to/cast into the starter motor itself -which has clearly been recon'd in the not too distant past (and a real sod to extract!).

 

Even amongst 50's Renners, I've not come across this setup -and stupdily want to retain it. I've moved most of the others to 12 volt -this one is (hopefully!) staying 6.

 

I think I need to find a good auto electrician to test this before I can go further ,sadly.

[Rocket88]

Would it be viable to use a "stand alone" solenoid"? If so, ebay item 110837549016 may be of use.

[Andrew353w]

A word of caution here:

 

6 volts is half 12 volts and a 6 volt bulb instantly blows when 12 volts is whacked through it. Similarly, passing 6 volts through a 12 volt bulb does make it light up, but dimly, and it doesn't light instantly but rather "warms to the task", eventually giving out some, but nowhere near the correct amount of light. More significantly it draws a huge amperage, at least to begin with, although this drops as the bulb's element warms up. The maths is as follows:

 

A 12 volt 55 watt bulb will draw just shy of 4.5 amps (55 divided by 12= [just over] 4.5 amps). But a 6 volt 55 watt bulb will draw over NINE amps (55 divided by 6= [just over] 9 amps) Put simply, half the voltage and you double the amperage to obtain the same wattage.

 

Maths lesson over. {mostly learnt from working on 6 volt cars for many years; try wiring up some 12 volt bulbs to a 6 volt battery through an ammeter & you'll see what I'm getting at!}

 

BUT if you connect a 12 volt bulb to a 6 volt battery the bulb's element (the wire that glows to give off the light) will not get hot enough to give off much light. As the bulb becomes hot it glows and gives off the light. More importantly, its resistance rises hugely and if it doesn't reach the operating temperature the bulbs resistance will be lower than it should be & will pass too much current, thereby blowing fuses and possibly burning out wiring.

 

If you apply this analogy to a starter motor and its solenoid, where HUGE amperages are involved it should be clear that not only would the solenoid possibly not engage smartly to start the car, but the effect on the battery might be tantamount to a dead short, until the starter wiring warms up and only then would the windings offer significant resistance to the huge flow of amps from the 6 volt battery. You might have a serious fire on your hands......

[Rocket88]

Fair enough.............................!

[panhard65]

Hi Nigel I have just tested the 6 volt fregate starter I have here and it works, but it is a cable operated one from an early fregate. Shouldn't be too much of a problem fitting a cable set up though. Let me know if your interested at the moment I have no plans to come your way but that can change depending on work

[nigel bickle]

Martin thanks. its certainly a fallback position. I can copy the Colorale -that has a cable op. I'll get back to you if I have to take that route.

 

Heres a poor pic:-

 

[nigel bickle]

Andrew- thanks. I'm aware of the connsequences of getting this wrong -hence the query. Potentially dangerous -as well as inconvenient.

 

''If'' I have been taken, by an 'Expert', in the full knowledge that it will def die, prob blow up & poss catch fire- I think thats cause for reasonable concern. if that is indeed the case- natch I will pursue it.

 

However, right now, I just want to know if its right or not -and kinda hoped some Sage on here would know that waving nettles & broccoli in an anticlockwise fashion at sunset, whilst bathing in warm honey -would point me right.

 

Back to the science I guess.

[jonny69]

I'd have thought 6V on a 12V solenoid wouldn't be enough to hold the electromagnet switch inside the solenoid and when cranking through it you'd hear it chattering. When my batteries have been dying in the past, 9V through the system is usually enough to make it chatter like that. Using that logic, I'd have thought that 4V is probably the minimum voltage that a 6V solenoid would operate at, but probably nowhere near enough to make a 12V solenoid click into life on the bench.

 

The trouble is, the only real way to know is to fit it up.

[nigel bickle]

Andrew has this spot on.The amperage if this is an wrongun is too high to be safe. Sadly -it wont be self evident immediately -either.

 

Got to find someone with kit..

[Craig the Princess]

Could you measure the resistance of panhard's 6v solenoid and compair to your one at a set voltage and current?

[nigel bickle]

Nice idea- but PH^65's is a mechanical solenoid driving a 6v motor. I have the same on one of my others. Totally different

[Craig the Princess]

Nice idea- but PH^65's is a mechanical solenoid driving a 6v motor. I have the same on one of my others. Totally different

 

Bugger. I guess the starter motor doesn't have a power rating on it to work back from.

[Andrew353w]

I just want to know if its right or not -and kinda hoped some Sage on here would know that waving nettles & broccoli in an anticlockwise fashion at sunset, whilst bathing in warm honey ....

 

Enough of your private life, Nigel.......

[Pillock]

From everything I know of oldschool electrical equipment testing, you can only compare like for like. Yes you can measure the resistance but that will only give you something to work on when compared to another, identical solenoid - a different 6v one could have a totally different coil arrangement.

 

Sorry! I'll ask our wise old electronics engineer when I see him next but that's not till next week.....

[garethj]

As said, if you've got another one you can measure the resistance of each. It might be worth digging through some old workshop manuals too, the ones from the '50s and '60s often have that kind of info. Even if it's not from exactly the same car it'll give you a good feeling.

 

I've run a few 6V VWs with 12V and haven't changed the starter or solenoid, they've worked fine. But if your new solenoid is for 12V then it won't fire with 6V and you're right that it'll be second hand by then.

 

Perhaps waiting until your old solenoid has arrived is the safest thing, then you can compare resistance of the windings?

 

Or are there any markings on the new solenoid, there should be a part number? Google could be your friend to see if it's 6V or 12V

[hairymel]

sorry to say i think the exploding 12v solenoid with 6v put in it is bollocks unless someone can explain otherwise!

 

 

v=IR

 

so

 

current(I)=volts(v)/Resistance®

 

so

 

for a fixed resistance(ie a 12v solenoid) if you halve the operating voltage it will halve the current drawn by it

 

conversely a 6v solenoid run at 12v will pull twice the current it was designed to and will likely assplode or melt your wiring.

 

 

p=IsquaredR

 

power=currentxcurrentxresistance

 

or p=vsquared/resistance

 

so Resistance=voltage squared/power

 

if the voltage is halved, to retain the same power output the resistance must be reduced to 1/4 of its original value

 

 

ignoring inductance etc if the solenoids exert the same mechanical push the 6v solenoid should have a resistance of approximately 1/4 a 12v one (or a 12 should have a resistance 4 times that of a 6v)

 

 

12v solenoid with 6v in will produce 1/4 the push

 

TLDR

 

12v solenoid will not work very well at 6v but it won't break anything.

 

connect a ammeter to the solenoid , connect it to 6v and if it pulls less amps than the fuse for the solenoid (but not much less than 1/2 that value) you should be ok - possibly

 

 

 

my head hurts now, its been a long while since physics @ and i have avoided googling

 

quite happy for someone to shoot me down though