Exciting day - rebuild of 78 coupe

[kentvette]

Fitted a relay into my main beam circuit today. A 30amp fused relay from Halfords did the job for £6, plus a few crimp connectors and bits of cable I had lying around (the power cable from the alternator is somewhat larger than necessary, but it was available). Even managed to get enough slack on the light green headlight wire to fit it into the relay without having to extend it, so nice easy job.

View attachment 13173

John, you'll have to do a little piece for VetteNews, with wiring diagrams for those of us with Poo-Bear sized brains! Our old '78 would probably benefit from a similar set-up.

 

[johng]

Yes, lights were cutting out on main beam. The wiring is pretty straightforward. There will be a diagram on the relay as below.
You need to cut the wire which goes from the dipswitch to the main beam bulbs (on my 78 it's a light green wire, not sure if it's the same colour for all years). The end of this wire which comes from the dipswitch connects to contact 85. The end which goes to the lights connects to contact 87. Then you need to run a power cable from the alternator stud to contact 30 and an earth to contact 86. The power cable should be at least 12AWG I used much bigger than this just because it's what I had.

 

[johng]

John, you'll have to do a little piece for VetteNews, with wiring diagrams for those of us with Poo-Bear sized brains! Our old '78 would probably benefit from a similar set-up.

Stephen, I don't think there is enough to it to make a Vette News article.

 

[Chuffer]

Thanks Johng , that`s just what I need to do on my 1980 . I always thought it was more complex than that .

 

[Mad4slalom]

Yes, lights were cutting out on main beam. The wiring is pretty straightforward. There will be a diagram on the relay as below.
You need to cut the wire which goes from the dipswitch to the main beam bulbs (on my 78 it's a light green wire, not sure if it's the same colour for all years). The end of this wire which comes from the dipswitch connects to contact 85. The end which goes to the lights connects to contact 87. Then you need to run a power cable from the alternator stud to contact 30 and an earth to contact 86. The power cable should be at least 12AWG I used much bigger than this just because it's what I had.

View attachment 13175

Thank you for the info johng.

 

[kentvette]

Stephen, I don't think there is enough to it to make a Vette News article.

John, having seen the instructions above, you may be right!

I haven't had any trouble with my lights (famous last words!) but I might look into that.

 

[Derek Nicol]

You need to cut the wire which goes from the dipswitch to the main beam bulbs (on my 78 it's a light green wire, not sure if it's the same colour for all years). The end of this wire which comes from the dipswitch connects to contact 85. The end which goes to the lights connects to contact 87. Then you need to run a power cable from the alternator stud to contact 30 and an earth to contact 86.

So, am i right in thinking that you are only using a relay for the main beam to use brighter main beam bulbs... your dipped beam still runs directly through the headlight switch? Can the headlight switch cope with brighter than standard bulbs for dipped beam?

I dont know why im asking, just out of curiosity.. ive never driven mine at night and probably never will.

 

[johng]

Yes you are quite correct Derek. The thing is there are only 2 dipped beam bulbs, but 4 main beam bulbs, so the current required for dipped beam is only half (or a bit less) than for main beam. Even with higher power bulbs it's not likely that dipped beam could draw more current than the original main beam bulbs. My dipped beam works for at least 45mins without tripping out (I've not traveled longer than that in the dark!), but main beam was tripping after a few minutes.

 

[Derek Nicol]

Yes you are quite correct Derek. The thing is there are only 2 dipped beam bulbs, but 4 main beam bulbs, so the current required for dipped beam is only half (or a bit less) than for main beam. Even with higher power bulbs it's not likely that dipped beam could draw more current than the original main beam bulbs. My dipped beam works for at least 45mins without tripping out (I've not traveled longer than that in the dark!), but main beam was tripping after a few minutes.

Ah, ok, that makes sense.. so you can upgrade to as bright as you want on the dipped bulbs without a problem.

 

[kentvette]

I changed the (inner? dip and main beam) light units from sealed beams to lamp units with bulbs and, I think, received 100/80 H4 Halogen bulbs with them. Alas, I can't find an invoice or any record of the purchase, so they may be the standard 60/55 items. I bought the units from Classic Car Accessories, who now do not seem to sell them for the UK market, only LHD, which was what I needed. At the time I discussed the need or otherwise for relays and the chap at CCA said I should not need them, but they may help. That ties in withe the "blurb" on their site about the 100/80 bulbs. But, either way, on dipped beam they are sooo much brighter than the originals! I stayed with the original sealed beams for the main beam lights and with the new units I get cars a kilometre up the road flashing me to turn them down!

I have no relay, and so far no issues, even after a few hours driving after dark.... But I do like the idea of adding one for safety.

 

[johng]

That's interesting Stephen, if you've got 100W main beams in your H4 bulbs, then even with the original sealed beams you must have around 300W in total when you switch the main beam on. I'm surprised that doesn't trip the circuit breaker. Also, I found that the original wiring loom sockets for my dipped beams had really suffered from heat (even with the old sealed beams) they were really brittle so I had to replace them. If you are pushing twice the current through them how well are yours holding up?

 

[kentvette]

That's interesting Stephen, if you've got 100W main beams in your H4 bulbs, then even with the original sealed beams you must have around 300W in total when you switch the main beam on. I'm surprised that doesn't trip the circuit breaker. Also, I found that the original wiring loom sockets for my dipped beams had really suffered from heat (even with the old sealed beams) they were really brittle so I had to replace them. If you are pushing twice the current through them how well are yours holding up?

Ah well, of course, I could have the 60/55 bulbs; without pulling one out to look, I have no idea now! (it seems to be the only invoice I cannot find!) But, when I made the swap I wasn't aware that the plugs or the wiring looked particularly "old", or brittle, especially considering where they "live". Now of course, I'm panicking!

 

[Mad4slalom]

Ah, ok, that makes sense.. so you can upgrade to as bright as you want on the dipped bulbs without a problem.

Johng, I bought a halfords relaytodsy and some reels of wire. The relay is30a four pin suitable for headlamps, but it is not fused, is it ok as the headlamps will have fuses or should I exchange for extra protection, do you remember what size fuse you used ?TiA

 

[Mad4slalom]

View attachment 7785

Wtf is with those pimp wheels

 

[Mad4slalom]

I'm very pleased with it Tim, especially as it only cost a very reasonable £3000

Wow that was a great price for a repaint

 

[Forrest Gump]

Stephen, I don't think there is enough to it to make a Vette News article.

This topic comes up quite frequently so it might be worth posting a new suitably titled thread and paste your instructions. It can then be searched and help other people (it will be buried in this long thread). Then you will get royalties of course.

 

[johng]

Johng, I bought a halfords relaytodsy and some reels of wire. The relay is30a four pin suitable for headlamps, but it is not fused, is it ok as the headlamps will have fuses or should I exchange for extra protection, do you remember what size fuse you used ?TiA

You need to have a fuse as the power for the main beams will no longer be coming through the headlamp switch. You can either use a relay with a fuse in it (as I did) or fit a separate inline fuse. My main beams draw just under 20amps, so I've gone for a 30amp fuse.
This is the relay I got.
Halfords HEF553 Relay 12V 30A 4 PIN | Halfords UK
John

 

[Mad4slalom]

You need to have a fuse as the power for the main beams will no longer be coming through the headlamp switch. You can either use a relay with a fuse in it (as I did) or fit a separate inline fuse. My main beams draw just under 20amps, so I've gone for a 30amp fuse.
This is the relay I got.
Halfords HEF553 Relay 12V 30A 4 PIN | Halfords UK
John

Thanks johng, we know that yours works so I will change mine for the fused relay , thank you.

 

[johng]

Managed to fix another electrical issue today. My heated rear screen wasn't working (not that I need it this time of year, but maybe in the not too distant future). I took the switch out and found that it was a bit intermittent, but with a squirt of WD40 and a few operations it resumed working every time. The rear heater still wasn't getting any power to it though. Looking at the electrical diagram the next likely culprit was the timer relay, which is high up underneath the dash panel (in fact on my car it was tucked inside the drivers A pillar). A real nightmare to get to, but after taking out the heater ductwork and lying on my back in the footwell I finally managed to pry it out. It would work as long as I held the switch on, but tripped out as soon as I released the on switch. As a new one seems to be $99 plus shipping plus vat, I decided I might as well take it apart and see if it was fixable. Not sure how well it shows in this photo, but there was a big pile of rust inside!



Apart from that everything seemed to be intact if a "little" corroded. This time it took a bit of cleaning up the contacts with emery cloth and a good squirt of WD40 to bring it back to life. I rigged up this test setup to check it all out before going through the contortions of trying to refit it. Even the electronic timer still works

 

[kentvette]

Good job John!

I occasionally wish our '78 had the heated rear screen, but it is in fact one of a very small number that didn't come with it - clearly the original owner didn't think he'd need it in Fort Myers!