Hi Guys,
 
So this all started a few weeks ago.
 
I pulled the motor out of the car to give it a bit of a freshen up. The motor is sitting in the garage, but I thought in the meantime I might repaint the headlight plastics etc and just get the front of the car looking nice. After putting it all back together I checked the headlight operation and high beams......and it all started falling apart from there.
 
I am blowing fuses when I turn the high beams on, but the problem seems somewhat intermittent. It blows EVERY time I try to use an 8amp white fuse, and "most" of the time when I use a 16amp pink fuse.......but after a bit of digging, the problem seemed to deepen.
 
The outer lights are sealed beam 60/55w, and the inner high beams are H1 55w globes. I think this is OK (IE: Standard)
 
I thought I had a relatively decent grasp on auto electronics (for older cars), but ill admit im now totally confused.
I got my multimeter out and decided to do a bit of testing.

If I run a continuity test between the black wire for the high beams, and the power wire for the high beams, there is continuity. Weird right.......?
 
If I run a continuity test between the black wire and the chassis of the body, there is also continuity. This seems to make sense to me.
 
If I run a test between the power wire and the chassis of the body, there is also continuity!. uh oh.....

To take it even further.......if I run a continuity test between the negative terminal of the battery and either of the power or earth connectors for the high beams, there is continuity.
 
Same applies if I run this test against the positive terminal of the battery. In other words, everything seems to be connected wether it be on positive or negative.!!!.......

I have no idea if this is causing (or part of) the problem, but I thought id better get my head around this before going any further, because now im just stabbing in the dark.
So, can anyone help shed some light on what might be going on here?. Am I having a brain fart moment and this is normal??.....is it some kind of weird English thing??......(cough cough).
 
I have done a visual inspection of the wires hanging around inside the car (the interior is also out), and the engine bay. I can see nothing noticeable shorting.
 
Really appreciate any guidance you can provide.
Dave
 

Dave, how are you measuring continuity? If you using a meter then 0 ohms on the +ve side is a concern, but youll always get continuity through the globes. I think the std headlight wiring has a connector at the lower front corners of the inner guards, try unplugging from the globes and again at the connector and repeating your checks

hey mate,
 
thanks very much for your reply. The device I am using to do the continuity testing is a decent mutlimeter of sorts that I have had for some time (pictured below)
 

 
I don't quite follow what you mean by 0 ohms on the +ve side??.
 
An additional piece of information I have:
I tested between either side of any of the fuses, and the +ve side of the battery, and got continuity. I think this is normal as the fuses run along the +ve circuits in the car?.
 
However, I also tested between either side of any of the fuses and the -ve terminal of the battery, and also got continuity!. Now this doesn't make sense to me. How can the fuses be in both the +ve circuitry, and the negative!?!?!
 
The tester simply gives me a continuous beep when it detects a continuous circuit. It does show me a bunch of numbers on the LCD, but to be honest I have never paid any attention to them. I kind of figured that if I got ANY continuity between the +ve circuit and the -ve circuit, then there was a problem?.
 
Thanks again for any help.
 
Dave 
 

All your high beams add up to 220w which equals to 18.3 amps. Is this fuse no4 you are blowing?not sure why you think 8amp would work. What fuse have you run in the past? Is there a high beam relay? If not I highly recommend one.

You could disconnect your inner high beams and try a 16 amp it definitely shouldn't blow, confirming there is no shorts in high beam circuit just a high load.

Cheers

Thanks RS2000......this post is relevant to what I have been figuring out in my own right.
 
I decided to stop being lazy, and have been adding up the current drawn from each light, using my multimeter.
 
Each light appears to draw roughly 4.1amps or so, so when multiplied by 4, equals the 16 odd amps you mentioned.
 
Clearly 8 amps is not going to work with this. But what confuses me is that this car (as far as I know) is completely stock. One owner, granny cat. How the heck has it ever worked!.
 
I put a 16amp fuse in, and sometimes it blows, sometimes it does.......lending itself to supporting the notion that it is right near the 16amp threshold.
 
So I now understand why its not working, but am really confused about how it ever worked.
 
Does anyone have a wiring diagram I could use to wire up a relay?/
 
Many thanks.
 
Dave

Dave if testing with engine idling you will find it will probably work as higher system voltage will result in less current draw, explaining why it worked in the past.

On top of the above you might have also induced slightly higher resistance at the connectors or at earth point causing slightly higher current draw just tipping the current draw over what the fuse can handle.

Cheers

Are you saying it worked with 8amp in the past?
Have you upgraded the headlights? I thought original outers were something like 37.5/50 watt? Not sure on inners.

Cheers

Thanks again.

I'll have to be honest and say I don't think it was ever on an 8 amp fuse....I think from memory it was a 16amp fuse.

The engine is out of the car, so idling is obviously not possible.

The outers are 60/55 which I have not changed. Is there any supporting documentation on the 37/50 watt suggestion, or are you certain of this?. Still puts the high beams over 16amps anyway.

One question. I'm pretty sure the previous owner of this car would not have had anything to do with the lights ever changed. So, how do the mk2 rs2000's come from the factory?. The manual specifies fuse 4 as being 8 amp.
If the car has never had any changes made to the headlights (which I believe to be true), then it must have been wired like this from the factory.?

I understand what your saying, the only way 8 amp would work is if only the inners were high beam from factory with somewhat lowish wattage sealed beams????

I run Stanley 37.5/50or 55 sealed beam outers and 150w inners with relay and modified wiring for high beam circuit as there is around 400watt of high beam. 37.5w low beam is perfect for 8 amp fuse operation. The factory sealed beam were probably some CP (candle power) rating equivalent to 37.5w thus it's existence.

Prior to my wiring modification RS already had high beam relay but wiring at the headlights looked untouched, can't be sure what is stock as I haven't owned it from new. Would also like to know for sure what headlight config was factory.


Cheers

I owned a 79 RS from new and it did not have sealed beams as we use to upgrade the globe to 55/100 and put 100w in the inners. The alternative for the inners was 100w sealed beam "landing lights". At that point you had to put a relay on the HiBeam circuit (it did not have one from factory). Adding 100w Driving lights then strained the alternator, so the trick was to delta wind it for the extra power. Biggest problem was the bad contacts in the fuse holder would turn all the lights off at 140kph  Ahhhh!
 
Graeme