Physical fitting of new Switches e.g for Hazards (basics)

[svenedin]

Despite the fact that I have owned my Morris for 34 years I am remarkably ignorant in some areas. I have carried out many tasks on the car over the years for example, today I am going to take the entire heater assembly out strip it down and refurbish it but I have never fitted a new switch. I have a great aversion to drilling holes in the car anywhere hidden or not hidden and have never done so. However, I think it is time that my car had hazard warning lights prompted by some fuel pumps problems (now fixed) that led to the car cutting out in traffic several times (it is dangerous). My question is not about the electrics which I can cope with (e.g following a circuit diagram, making up wires in the correct colour coded wire, crimping on connectors etc) but the physical mounting of switches.

How does one drill holes for a new switch? Say, I wanted to mount a switch under the dashboard. Yes, I can mark the holes through the bracket but are there any tips to avoid the drill slipping and making a mess? What about how to choose the correct drill bit and screws? Presumably self tapping screws as used elsewhere in the car but what about sizes? When a screw is quoted as a certain diameter that seems to include the thread so what size hole should be drilled? I really have no experience of drilling metal.

I am looking at this hazard kit and I wonder whether I could avoid drilling altogether by using strong self-adhesive velcro? This particular unit has a nice large mounting plate that look like it could work.

Thanks for any guidance that can be offered

Stephen

This kit is cheaper from ESM but there are better photographs here:

https://www.autoelectricsupplies.co.uk/product/215

[oliver90owner]

My advice is to fix it so that is permanent - not with any possibility of it not being in place when urgently required. Therefore glued permanently or screwed.

For screwing, there are choices. Self tapping screws or machine screws are the usual choice. On the edge of a panel there is the possibility of attaching clips for screw attachment - better than self tapped holes in thin metal.

With regard to drilling holes - the size is possibly a variable which may require some selection. Self tapping screws require a drill bit that is neither too tight nor too loose. Obviously better to start on the small side! Machine screws normally require some clearance, but for small screws the same size of drill may be adequate (many screw threads are less than the nominal size as 100% thread engagement is not a reality) but normally, for small screws 0.5mm is adequate. Screws with only part-threaded shanks should require a clearance hole.

There is a drill type made for accurately spotting hole positions (called a ‘spotting drill’, surprise, surprise!), but usually only used by machinists when operating milling machines (and sometimes lathes). For this sort of job a short stub drill is generally more than adequate.

Taping the surface with insulation tape etc., and marking the hole-position for the first hole, followed by careful drilling is usually all that is needed. An alternative is the careful use of a centre punch to mark the spot.

The subsequent hole(s) can usually be drilled with the item in situ. A pilot hole is often required, if the fixing screw is very close to the hole size in the item being fixed. Indeed, a small drill bit is easier to get drilling, at the required position, than a larger drill where the drill point may not be perfectly formed for starting a hole (that is why spotting drills are used by machinists).

Nothing difficult, really. Experiences, with failure, will concentrate your mind when carrying out these minor operations.

[simmitc]

I would not rely on tape@ When you need the switch, you need to be able to use it without it dalling off!. Put masking tape over the area where you are going to drill and mark that. Use a centre punch to get the centre of the hole and then start with a small drill and work up to the size that you need. For example, 1/16, 1/8, 3/16 or 2mm, 2.5, 3.2 etc.

[King Kenny]

I have a Variable speed wiper switch and dial fitted to a right angled bracket that is held in place under the dash with two very small nut and bolts. The fittings are not visible unless you lay on the floor and can be removed if necessary. If I remember correctly, there are several such screws already fitted in this way.

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[simmitc]

Kenny, you might want to revise that picture - it gives a registration number and the position of your "secret" fuel pump switch

Stephen, depending on the year of the car, you might be able to use the bolts (cross head machine screws) that hold the glovebox surrounds in place.

[myoldjalopy]

Its much more sympathetic to fit additional switches under the dash (like in Kenny's pic), rather than molesting the car by drilling holes in the dash....

[svenedin]

Thank you very much for the replies and advice. I will screw the switch on as recommended. Over the weekend I will try to ascertain potential mounting points for a hazard switch. This is a very good opportunity because I took out the heater today for overhaul (a horrible job I thought) and both gloveboxes are out at the moment. I want to re-site my flasher relay as well. I changed to an electronic relay when I swapped my bulbs for LED. This relay does tick-tock like the old one but either it is quieter or I am going deaf or both so I want to move it from the bulkhead to under the dash. I propose to do that by connecting to the existing flasher relay connections on the bulkhead and coming back through the bulkhead to a suitable mounting point under the dash or possibly behind the driver's glovebox. I have cable of the correct colour and trace to do this.

Stephen

[svenedin]

Its much more sympathetic to fit additional switches under the dash (like in Kenny's pic), rather than molesting the car by drilling holes in the dash....

There's absolutely no way I am going to drill holes in the dash!!!!

[simmitc]

One more thought about drilling: Always check what is behind where you are about to drill. You do not want to drill into any wiring or fit a screw where the tip of the screw will be in close proximity (or even touching) any other electrical component such as a blade terminal on a switch.

[svenedin]

One more thought about drilling: Always check what is behind where you are about to drill. You do not want to drill into any wiring or fit a screw where the tip of the screw will be in close proximity (or even touching) any other electrical component such as a blade terminal on a switch.

Sound advice. Thank you.

[cyrus]

Another option is to use the mounting point for the heater control valve, make a wider bracket that will accomodate both heater control and a switch as well. No new holes to drill in the car.

[geoberni]

I fitted a switch of a similar style, i.e., 2 upward screws and mounted it far enough back under the dash that it doesn't stick out noticeably. A couple of small drill holes, if none in the right area, which some cars may already have collected over the decades.
The secret to fitting a switch or anything requiring holes drilling is to...
1 - Mark the hole positions with a pen/pencil.
2 - Use a punch to make a small dimple in each position
3 - Drill small holes perhaps 2 or 3mm or so, using slowish drill speed and not pressing too hard
4- If larger hole reqd then enlarge with correct drill bit.

Steady and patiently is the key to not having the drill bit skid off across the work area.
Mine is tucked down by the side of the steering column.

[svenedin]

Another option is to use the mounting point for the heater control valve, make a wider bracket that will accomodate both heater control and a switch as well. No new holes to drill in the car.

I like that idea. I'm not sure I have the skills to make a new bracket myself but I am sure I can find somebody who can.

[svenedin]

I fitted a switch of a similar style, i.e., 2 upward screws and mounted it far enough back under the dash that it doesn't stick out noticeably. A couple of small drill holes, if none in the right area, which some cars may already have collected over the decades.
The secret to fitting a switch or anything requiring holes drilling is to...
1 - Mark the hole positions with a pen/pencil.
2 - Use a punch to make a small dimple in each position
3 - Drill small holes perhaps 2 or 3mm or so, using slowish drill speed and not pressing too hard
4- If larger hole reqd then enlarge with correct drill bit.

Steady and patiently is the key to not having the drill bit skid off across the work area.
Mine is tucked down by the side of the steering column.

I will definitely invest in a centre punch. This is where I have gone wrong before (not on the car) and the drill has slipped and made a mess.

[geoberni]

Just FYI, here's a photo of where I mounted mine, to the right of the steering.
That way the cables on it reached out down the wing to the DB10 Relay for the '61-63 style indicators that are installed.
I have no idea why a past owner chose to fit the loom and relay for that when they refurbished Basil, because they then altered the wiring to separate the brakes and indicators....
It's above my vintage 1951 Fire Extinguisher, which is still charged with a sealed canister of Carbon Tetrachloride, ...but I'm happy with the risk that poses if I should ever have to use it. Being a sealed replaceable canister, I've been able to check that the actual operating system is functional.

20230126_103256.jpg (1.4 MiB) Viewed 1026 times

[oliver90owner]

I would prefer a more central position - where it could easily be operated by a passenger, if required

[svenedin]

I too would prefer a position whereby both driver and passenger could operate the hazards. I am not sure finding such a position is easy though. I will have a look tomorrow. This is an ideal opportunity as I have both gloveboxes out and the steering wheel off (I am overhauling the heater and I fitted a new indicator stalk assembly today). Off topic: fitting the new indicator stalk assembly was a slight nuisance. The new Lucas part appeared identical except having wires that do not follow the standard British wiring colour code in cars of the era. For instance, the wires for the right indicator are the same colour in a Morris Minor, MGB B, Land Rover or whatever. Rather annoying because the standard was adopted largely influenced by Lucas.....Anyway, I now have self-cancelling indicators once again!

[geoberni]

I would prefer a more central position - where it could easily be operated by a passenger, if required

I've never understood that argument; the point was raised 2 years ago, even with unsubstantiated claims that it was in the MOT or was 'the law'....
viewtopic.php?p=663324#p663324

[oliver90owner]

I was not arguing a case. Anyone can put wherever they like. It is just my preference.

[geoberni]

I was not arguing a case. Anyone can put wherever they like. It is just my preference.

Sorry, I didn't intend that you read it that you were 'arguing a case'; just saying that the 'location question' had been put forward before, with 'fake news' legal position for it, even claiming it was part of the MOT!