Headlights: add relay or not?

[lotuselan2]

I have read previous posts about low voltage to the headlights when not
using a relay. I decided to measure mine yesterday. I did the test with
the motor off but the batter fully charged. The voltage at the headlights
was 10.5 V and 12.0 V at the solenoid. So I am losing 1.5 volts in the
switch and wiring. This would equate to 12.5 V at the headlights with
engine at normal RPM and 14 V from the alternator (which I have). My wiring
harness is 100% mine with larger gauge wire throughout, but light power is
going through the dimmer switch.

My question is, would you expect lighting to be brighter by switching to a
relay system and only putting the control power through the switch?

Ken

[dlbarnes1]

I suspect the voltage drop is occuring at the switch(s); the dimmer switch
and the headlamp switch. The contacts of these switches will become worn
from breaking the headlamp current, the contact resistance will increase,
and, eventually the switch fails. Also, if power for the headlamps comes
thru the ignition switch (no relays) there is another possible voltage drop.
I found that my ignition switch has a resistance of 0.3 ohms (probably
should be replaced). If the headlamp current is 5 amps, a 0.3 ohm resistance
results in a 1.5 volt drop.

Relays not only have higher current ratings for the contacts, but they are
also more feasible to replace if they fail. I replaced the headlamp relays,
not because there was a failure, but because they were over 20 years old as
well as simple and inexpensive to replace.

Add the relays. Not only will there be increased voltage at the headlamps,
but the wiring system will be more reliable.

Dave 72 Sprint DHC

[bill308]

Ken,

I concur with Dave and Sean. Fit the relays. Your switches will like
it and so will your eyes. Use of at least 14 AWG wire, of minimum
length, for the power circuit will enable the retrofit of better
(higher wattage - like Cibie E-code lamps) lighting or improve the
performance of your current lighting.

Bill

[lotuselan2]

All my wiring is 12 or 14 gauge with few exceptions and I made a complete
figure-8 ground loop around the car to maximize ground-side resistance. All
of my wiring is compact; relays will be fitted just between the power supply
fitted off the solenoid (which is only a terminal block since I have a gear
drive starter) and my fuse blocks on the RH inner panel. Each light's high
and low beam are separately fused, so my only voltage drop now is the dimmer
switch which will go out of the power loop with the relays.

If I ever add extra driving lights I will have plenty of power for them.

Ken

[lotuselan2]

Dave

The main voltage drop issue is likely the dimmer switch. I have a more
robust switch for the lights than standard and the ignition switch
definitely does not carry the lights (mine will stay on with ignition off,
the way I planned it). I have heard of voltages as low as 9V in group
postings. As I said, my wiring is one or two gauges larger than stock so
wiring is not an issue, but smoke coming from the dimmer switch is expected
at some time when it would do the most harm!

I already have relays so I will find the time to get them installed, since
there is more nighttime hours these days.

Thanks for input.

Ken

[fatboyoz]

Sean,
Any clues on how to insert relays into the wiper and window circuits.
Thanks
Colin.

[Garibaldi]

Figure 8 groundloop?

[denicholls2]

Colin wrote:

Sean,
Any clues on how to insert relays into the wiper and window circuits.
Thanks
Colin. 68S4DHC

In both cases, the original circuit remains but the power side is
disconnected a short distance from the motor (leave enough for
connectors, etc.) As recommended, 12 0r 14 guage (but no thinner!) wire
of an appropriate color and manufacture is run directly from the power
terminal of the battery to the same area.

- The motor wire is attached to the triggered (output) side of
the relay.

- The power wire is attached to the triggered input of the
relay

- The original wire is attached as the trigger for the relay.

- Ground is supplied to the ground terminal on the relay.

Be extremely carefully in running the power wires that they have no
opportunity to chafe. Remember, these wires will be hot all of the time
(unless you are wise enough to purchase and actually get around to
installing a battery cutoff) and are a wonderful source of electrical
fire if done badly! For this reason, I would recommend regular
inspection of the power wires going to the window motors where they must
move each time the door is opened. An alternate approach would be to
place these relays just inside the doors and let the old wire carry the
current through the bendy areas. Remember, though, that it's probably
been bent back and forth for 35 years or so...

-- Doug Nicholls, 54/1822 Ma~

[lotuselan2]

Colin

I wired my window motors to work with the ignition off. So I have direct
wires via 12 gauge wire from power to switch to window. Yes, the switch
takes the load but they move quite well without relays. On my Europa I
always turned the key off and then tried to raise the windows and it ticked
me off. So I did it my way.

Ken

[lotuselan2]

Doug and Colin

A fuse is highly recommended for the main power. The power to the switch is
likely fused already. If you don't want to run via the fuse box and in-line
fuse close to the power supply would do. It beats using a fire
extinguishers.

Ken

[poiuyt]

Add a fuse as close as possible to the power source. This should be
SOP with any power wire.

Steve B.

[denicholls2]

Ken wrote:

A fuse is highly recommended for the main power.

Excellent point, Ken.

One concern in this is that like the original cars, a small number of
fuses results in a fuse that is too large to actually protect the wiring
in the circuit. This can be minimized by running multiple power wires.
My suggestion if you choose this approach would be to separate the
lighting circuits from the others. Lighting is the highest drain in the
older Loti, followed by running multiple motors (heater, radiator,
window) together. (The starter is the highest drain but already has its
own relay circuit). Modern audio equipment is also capable of high
current draw, though a vintage radio would not factor highly in this
equation.

In addition to fusing the large main circuit(s), consider separate
in-line fuses on the individual loads. For example, the circuit that
carries the window motors needs around 30 amps of fuse in the event both
switches are hit simultaneously. A single 30-amp fuse is not likely to
blow before the motor wiring in the event a switch sticks on (which the
Europa switches are prone to do.) Two 15's provide real protection for
the components.

Also consider using breakers instead of fuses. I understand there are a
number that are well-suited to automotive applications. In the Europa
list archives somewhere there's a reference for breakers suitable for
the window motors.

-- Doug Nicholls, 54/1822 Ma~ (Need to get around to all
of this sometime)

[frearther]

Motors for radiators (fans, I presume) and windows? That sounds like
newer Loti to me >:-} . But of course, I'm still stuck in the sixties
(decade, not age - I'll never see that again).

Art

[lotuselan2]

Doug

I wired my car with 20 fuse positions (fifteen in front and five in the
boot); I think I actually used 18. For example, each headlight has a
separate fuse for high and low beam (four total). I used modern push in
fuses. I think I used one 20A fuse with heavy gauge wire for both windows
and the operator is clever enough to operate one at a time. The Prince of
Darkness does not live in my garage.

Ken