electrical overload with Halogen lamps

arthuy

Well-Known Member
I have a problem with fuses 11-12 & 13-14, the mian beam inner and outer.

These lights used to work periodically, this I traced down to dirty connections and thought nothing of it. There was also a bit of crappy wiring which was not rover spec.

I Changed to Halogen and the original problem was still present as I never really got stuck into it.

Whilst doing some prep for the MOT I had all the lights on at once, when I went to turn them off after about 7-8minutes there was smoke coming from the glove box. the top fuse holders 11 and 13 had melted the plastic.

I decided to remedy the problems by replacing the box and any fuse holders which were beyond cleaning.

I did this and all the faulty electrics are working as they should. I did notice that the same fuses were hot, not wanting to melt my only spare fuse box I turn the lights off. I had fitted a 15 amp and 25 amp fuses as per the box.

I am wondering whether I should be upgrading the circuits for these lamps. or does anyone have any suggestions
 
The fuseboxes on these car are pretty inadequate when adding modern stuff like halogen lamps.

You're best bet maybe to fit relay switched secondary fused circuits for the lights. The last thing you need is an electrical fire, especially on a dark night with all the lights on !

Richard
 
Thats what I was thinking.

Does anyone remember which magazine the "Bright eyes" article I can't recall the month off hand.
 
Arthuy,
twas me that wrote the original article "Brighteyes" in Feb 2002. Before I installed the higher wattage sealed beam units in my car I telephoned the recommended electrical chap named in the back of the magazine (Steve Hopkins 19-07-01) who was very chatty & assured me that everything would be fine. ( 75 watt replaced 37½ watt!).
October 2002 I was back with "Brighteyes - The Sequel" in which I had fitted Lucas Halogen lamps in main and dip beams.
These bulbs are 55 watt and hence should not overload the circuits. The bulbs themselves run hotter and they are much brighter but they take no more power. A bad electrical connection will form a "hotspot" but your new fusebox and clean contacts should have solved any little problem. I believe old wiring can increase in resistance with (considerable) age and should be removed - Do you have an ohmmeter ?
Hope this helps, regards, John.
 
For about 2 years I have been using Semi-sealed dip/main lamps which take modern halogen bulbs-the same fitting as the last 200 (before it became the 25) with no problems at all, bar the usual rusty earth/bits dropping off issues, and dip beams that are brighter than the old mains, and you can change the bulb for under a fiver.

They came from the Triumph Stag Owners Club shop in Headcorn, and cost under £40 for the pair (I can dig out a phone number if anyone wants), and fit just the same as a sealed beam.

TTFN

Matt
 
John,

Thanks for that.

I will poke around with the meter.

I was suspect with the connection prior to the melt down I saw a pretty blue arc.

The new box was used but I cleaned and replaced connections as required.

I had them on for a good few minute and felt the heat. since the midges were eating me I called it a night.

I think it is strange that there is a lack of relayed circuits on the P6. Modern cars seem to have them for everthing Head lamps, headed screen, horn, etc.

I will go draw out the lamp circuit and calulate the values. I will then see what the meter says can afford to melt another box.



Just for interest to other members.

There are plenty of cars which use these 5 3/4 inch units. Triumphs, Jags, Fords, Mazda MX-5!!!

The halogen replacement units are avaible new for around £50 a pair. Lucas and Hella make them

If you are wanting a bargin then look out for Capri's or Jaguar XJ40's in your local scrappies.

My personal bargin was 4 of the light units from a Jag including 4 Bulbs (the bulbs would have cost nearly £20 if bought from Halfords) I also got a pair of tailgate struts for an SD1 (£40 throught the owners club). and all it cost me was £30. Get the bargins before they get crushed.

 
There is a problem with using an ohmeter in this situation, there is a viscious cycle at work here and all will be fine with the circuit cold. The problem is heat and expansion, at a typical connection i.e. where the cable is connected to the fusebox there will be two types of metal present. as the connection heats up it loosens causing resistance, resistance causes more heat, more expansion more resistance etc 'till fire. most electrical problems of this nature are detected with thermal cameras (not practical) so use yor fingers to detect heat. find the hotspot and this is the weak spot. the design of the rover fuseboard may just not be up to higher currents at the f/b terminations. sorry long winded reply lol it's my electrical background.
 
Waldo,
I like the (almost throwaway) remark at the end of your message "It's my electrical background" - Do you have electrical experience / qualifications which would allow you to offer professional electrical advice to our members? I'm sure that it would be appreciated if you can as many of our members make electrical modifications to their cars.
Regards, John.
 
update on the hot fuses.

I cleaned the fuses till the sparkled. Problem didn't go away.

What I have done is soldered the connectors together. there is still a noticable warmth. I haven't bypassed the fuses just making sure there is an equally good connections.

This seems to have made a difference, certainly reduce the heat build up.
 
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