Starter relay coil resistance

S

smudger

Member
Does anybody know for sure what the starter relay coil resistance should be on a Series 1 3500? Mine has been replaced at some point by a previous owner with a modern relay but the original relay was left in place.

I have removed it and had a look inside where all looks clean and sound but if a section of the coil is bypassed due to an internal fault then although it might register continuity on a multimeter it wouldn't generate enough magnetism to pull in the armature. I'm guessing that is the problem.

I assume there must be something wrong with it or else it wouldn't have been replaced, but if someone knows what the coil resistance should be I can at least test that and then go from there.....
 
Hi, A quick google giving two answers, one says 76 ohms and the other says 70 to 100 ohms. So take your pick.

Colin
 
Hi Colin,
Thanks for that - is that resistance definitely specific to our relays? On Google I've found resistances ranging from 320 ohms to 900 ohms quoted for automotive relays depending on make and application. I couldn't find anything specific for the P6 starter relay although as a standard period Lucas component I'm guessing it would also be used on other cars of the time?
Simon
 
Not sure what starter is on the vehicle in question, . Are we talking about a relay to operate the starter solenoid or the Starter solenoid itself ?
 
roverp480 said:
Not sure what starter is on the vehicle in question, . Are we talking about a relay to operate the starter solenoid or the Starter solenoid itself ?
Click to expand...
The relay itself that is attached to the driver's side inner wing near to the brake fluid resevoir.
 
Ok cheers, I must have missed that one then, mine is reading only 35 ohms across the coil terminals so there is the problem.
 
Yes it is a 6RA although I'm never confident about assuming that similar-looking components fitted to different makes and models have the same spec. It can be all too easy to get caught out by thinking internals are the same from one make to another when they often aren't. It looks like a lot of Triumphs use the same relay to control overdrive but if they are working at the same resistance I don't know. Then again in this case they're probably all exactly the same......!
 
I had a feeling that they wouldn't be. Ideally I'd measure the resistance on one on a car where it is working correctly unless Colin can confirm the info on Google is definitely P6 specific? No matter, the modern relay is doing the job anyway but it's this isolation, it's now got me just poking about trying to find bits of old car to test to relieve the boredom......!!
 
ISTR but could be wrong, that there are some 6RA relays with 3 pins where the C2&W2 are combined, some 5 pin ones where there are 2 C1 outputs, some other 5 pin ones where there is still 2 outputs but one is live with the relay dormant and the other one is live when the relay has been activated, and of course the 4 pin one we have on the wing. Don't know about coil resistance but if it works, why does it matter?
 
The modern replacement works, the original presumably doesn't. If it is something that is fixable then I can keep the old relay as a spare or help someone else out with it if their's fails. If it is beyond repair then so be it but I'd just like to know why.....
 
Hi, Yes as suggested 6RA are the type or family of relay and can be configured differently either internally ie changeover relay or internal connections. either way they use the same coil unit. Just like the modern 'oxo cube' relays, where there are even more different ones.

Colin
 
Well if they all the 6RA family use the same coil unit then I'm guessing the resistance should at least then be the same regardless of whether its a 3, 4 or 5 pin relay or its function on whatever car its fitted to. Like I say mine is reading 35 ohms so if 70-100 ohms is the standard resistance for a 6RA relay coil then that's why mine has had it.
 
Quick google and - that would be a no :(. I don't know if one of these is the one used on the P6, but they are all different resistances

relays009.jpg
 
The SRB111 is a very common fitment to 60s/70s cars and is quoted as the starter relay on the MGB. Also used to control overdrive or horns on several Triumphs - that could be the one - and it is 70 ohms in the diagram.
 
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