MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - What Relay and from Where??

What relays (name/brand/part number) and from what source/store are you using for your headlamp circuits? I have been using Lucas 6RA's (I thought I'd keep it all English at the time I originally installed them) for 20 years on a 65B but after having switched to Halogens recently I now see signs of excess heat on the low beam relay, and seems to be running hot (the relay) even after having gone through all connections. Now that I run headlamps even for daytime driving, and as I don't know the amp ratings of the Lucas 6RA's (the insides don't really look too high amp) I thought maybe it is time to update/uprate. Thanks in advance for your time and consideration.
Rick

Got one for my heater at Radio Shack. Seems like they would have variety. Might also check with Jeff Zorn at LBCCarCo or Ed at British Wiring. Almost sounds like a bad connection or ground but I am no electrical expert it sounds like you know what you are doing. Paul Hunt has details on his web site and you might check and see what he is using.


JTB
J.T. Bamford

Rick

I am using the J C Whitney Heavy-duty headlight and Accessory Relay Kit, 30-amp, 350-Watt Capacity. The "kit" which includes the connector is $7.99. SKU#ZX149433Y. More than enough capacity for any headlights that I have seen.

FWIW

Larry

Larry Hallanger

I went to the local wrecking yard and got the relays and mounting block from a late model mercury. The block held three relays and I cut off their pigtail wiring from the car. Total cost including three relays and mounting block was only $5.00.This gives you a neat clean already mounted set of relays.
Sandy Sanders
conrad sanders

http://www.waytekwire.com/
Dan Masters

Rick - Your Lucas relay may be heating up because it is not intended for continuous use (I don't know this for sure, but that is the usual reason for relays to overheat). The part of the relay that is overheating is probably the coil from having 12 volts on it contenuously. Larry's suggestion of the relay from J
C Whitney is probably a good choice (just expect to pay as much or more for shipping as for the relay). Another choice is the Bosh type relay, also called ice cube relays due to their small square shape. You will need up to four of them since they are just single pole relays, but they are rated at 30 - 40 amp contact current and work well for continuous use. This type of relay is available at Radio Shack and at most auto parts houses. For more information on relays and how to wire them check out the following web sites:
http://www.danielsternlighting.com/tech/relays/relays.html
http://www.mgcars.org.uk/electrical/
Good luck - Dave
David DuBois

Dave makes a good point regarding the continuous current capability of the relay contacts and coil. However I have been using Lucas 6RAs on my Gt for the last 7 years for dip and main beams and another one for the driving lamps. Incidentally,all my lamps are halogen but are street legal
Iain MacKintosh

As David implies there are many types of Lucas 6RA and several with the same contact and terminal arrangements, but they do differ internally. For that reason I always use modern after-market relays for additions, but the correct type of 6RA for replacements. Typically relays used for relatively continuous use i.e. ignition, cooling fans, heated rear window, overdrive have a relatively low power winding to limit the heat that develops. Those for intermittent operation like the starter relay have a high power winding to give a very low contact resistance for the relatively high current requirements of the solenoid, and will get very hot if used continuously. Poor contact resistance also results in a hot relay, and low voltage output. I've never seen rating information for the 6RA but I'd bet it is lower than the aftermarket types now available.
Paul Hunt

David...that Stern site is the best explanation I have seen. Thanks.
J.T. Bamford

"You will need up to four of them since they are just single pole relays"

Bosch "ice cube" relay part number 0 332 019 151 has two output terminals. They may be hard to find locally, but Waytek carries them.
Dan Masters

Dan - The two output terminals just make them a double throw relay, not a double pole. A double pole relay would have two input terminals and two output terminals. This is not to say that they don't exist, but all I have seen are the single pole, single throw or double throw. I have not looked at Waytec yet. Cheers - Dave
David DuBois

Thanks so much for all the help everyone. To take it one step futher, what I'm looking for is "local" availability...Autozone, Checker, NAPA, Bumper to Bumper,...you know, the types of stores likely to be available wherever you may be, with a good, afordable, available (in stock) relay. I tend to travel with my own onboard spares, but will be convincing others to do the relay conversions also.
J.T., I will check out the Radio Shack stuff, thanks!
Larry, the JC Whitney sounds great...could you send me a relay number so I can check for replacement availabilty? Thank You!
Conrad, your solution was my first inclination, but local yards are not what we call "fabricator" friendly. Could you give me a specific car application to ask for? Also a relay number to check with the dealer for replacements. Thanks!
Dan, excellent website reference, catalog ordered. Thanks!
David, my thoughts exactly on the Lucas'. Excellent websghts,Thanks!
Ian, yeah, my 6RA's have been on 20 or so years, no failure, Cibie's most of those years but GE's for the last 3-4. Just thought I should revisit the subject with modern tech and thought as I did all mine as brainstorm back then. There wasn't all this great help from all of you available then. Thanks!
Paul, exactly! What aftermarkets are you using, from where? Thank you!
Dan, that Bosch number and the Stern web info is probably the ticket. Thanks!
Again, my thanks to all for the time and effort it takes to help someone on this websight. It really is appreciated, and by more than just the poster of the question I'm sure.
Rick

Dave,

Actually, they're not even a double throw, they're just a single pole, single throw relay with two output terminals, but they do allow the use of just two relays for the headlights - one for high beams and one for low. For each beam, one side of the car is wired to one of the output terminals, and the other side is wired to the other output terminal. The common input terminal is wired to power. These relays have two "87" terminals but only one "30" terminal. A single pole, double throw relay has one "87" (normally open) terminal, one "87a" terminal (normally closed), and one "30" terminal (Bosch part number 0 332 209 151)

In a separate e-mail to you, I have attached diagrams for the two relays.

These are the relays I use in the wiring kits I manufacture.
Dan Masters

Rick

See http://www.jcwhitney.com/autoparts/ProductDisplay/s-10101/p-256/c-10101 for the relay kit and the replacement relay. For a couple of bucks more you can get the relay with a fuse included http://www.jcwhitney.com/autoparts/ProductDisplay/s-10101/p-2926/c-10101

Larry
Larry Hallanger

An 'ordinary' single pole single-throw relay with only one output terminal will supply both sides perfectly happily. Personally I have not found any of the relays Dan describes, and it would make more sense if those were *double*-pole single throw as that would halve the current through the contacts. But even 30 amp relays should be adequate for up to 200W lamps and you can get 70 amp :o) Unlike Daniel Stern I fused the filaments (four fuses), and supplied both relays with a single additional fuse rated at least double the filament fuses. If you use fused relays the fuse is only protecting the bit or wire between the relay output and the filament fuses input, which is probably on a matter of six inches. My single fuse was located where I picked up the brown supply and hence protects the wiring *to* the relays as well as from the relays to the filament fuses.
Paul Hunt

"An 'ordinary' single pole single-throw relay with only one output terminal will supply both sides perfectly happily."

Absolutely true, but it is a bit easier to wire the relays with two output terminals. It's a lot easier to terminate only one wire in a given terminal than two, especially when you are using the recommended heavier gauge wire.

"Personally I have not found any of the relays Dan describes"

They are rather hard to find. I buy mine, in lots of 50-60 at a time, from Waytek, http://www.waytekwire.com/

You can find complete specs for all 12 volt Bosch relays at http://www.chiefent.com/products/products_relays.asp

Waytek also sells individual relay sockets (gangable)and terminals so you can wire your relays from scratch and not have to splice into salvage yard relays, and the relays can be removed and replaced a bit easier if you only have to pull them out of the socket, as compared to pulling 4-5 wires off each relay. Certainly not a necessity, but it does add a bit of convenience, and, I think, a bit of professionalism. Add-on fuse holders are also available to gang with the sockets, and you can wire the fuses as you wish.

I have no financial interest whatever in Waytek, but if you do a lot of electrical work, I do recommend getting a copy of their catalog. When I give wiring seminars at various club gatherings, I usualy bring several copies to pass out to attendees.

"Unlike Daniel Stern I fused the filaments (four fuses),"

In my opinion, if you are going to use fuses at all, it is MANDATORY that you use four! I have written to Stern about this, and he agreed with me and said he would change his site to reflect this, but he has yet to do so.

For fuse holders, I recommend buying the four-fuse blocks from Auto Zone or similar, holding four blade type fuses (not all auto parts stores here in the US carry these). These come with the terminals loose so you can wire them yourself without splices. Four terminals are supplied individually, and four are ganged together in a "buss bar" arrangment. I cut the buss bar in two, and feed each half individually from the relays (this really helps if you don't have the extra terminal on your relay). I drill two holes in the side of the fuse holder and screw the relay sockets, ganged together, onto them so I have one compact unit to mount in the car. Works quite well.

If you don't need the "buss bar" arrangment, Waytek sells these also, with individual terminals available seperately, but no buss bar. They cost a lot less from Waytek, but they are only $5 otherwise, so not a real big deal.

"My single fuse was located where I picked up the brown supply and hence protects the wiring *to* the relays"

Ideally, as Paul has done, the fuse should be placed as close to the power source as possible. Any wire between the power source and the fuse will not be protected.

For more general information on this topic, see http://www.britishv8.org/tech/mgpanel.pdf
Dan Masters

Rick,
You may find them at Fistell's Electronics in Denver. Funky old place downtown kind of out 60's geekdom but have everything. Outside looks like they are closed. Called them this morning and got part # to look up on internet site to be sure that is it before going down. Will email you off site and post later here.
J.T. Bamford

Check with the places that install high-power car stereos. They use a lot of relays. I got a relay kit from the local Circuit City....
Rob Edwards

I agree with Dan regarding the sockets. They are certainly not necessary but make the whole installation easier and much neater. Another place that carries the relays (although not the variety that Waytek carries) is MCM at http://www.mcmelectronics.com They don't sell the Bosh relays, but carry another brand of the same ISO 7880/7588 relay and sockets. Cheers - Dave
David DuBois

This thread was discussed between 21/10/2004 and 23/10/2004

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.