The Triumph Dolomite Club - Discussion Forum

I've given up trying to fix the conductor bonded on the inside of the glass - the silver paint just ain't doing it. So I'm fitting a small fan heater on the back window ledge, with DSS tape (I don't believe the 150 Watt description for ten seconds). But I just found that the light in the pull switch under the dash (73 Sprint) only comes on when it feels like it.

Are those switches reparable or is it a waste of time even taking it out from under there?

Also, if I can't fix it, anyone know of a suitable replacement?

Graham

The light in those early switches works independent of the actual switch. IE the switch part will work, even if the light is erratic. Try unscrewing the knob bit and having a cleanup, maybe replace the bulb. In dire need you can use the switch from a late car's rear foglight and just swap the knob over, think the wiring colour codes may be different but that's not a big deal! The switch is identical in function and fit.

For the HRW itself, I find no cure is better than fitting a working glass, I have a couple of spares.

Steve

Is this the right switch?



Graham

I had the switch out and took the knob off to see. It looks like the problem is the spring in the knob that bears on the bulb glass. It looks twisted out of shape, so maybe I'm not the first to look at it. But I tried re-shaping it and only managed to bust the bulb glass as a result.

I put one of those COB type LEDs in there, but the spring then screwed past the front plate. So I've put a bit of plastic (cut from the packaging from some soft tacos) between it and the spring, but it's still only intermittent. Maybe I need one of them new ones off ebay for £30.

But before that, I'm going to see if I can get one of the LEDs with a plastic dome that the spring can't bust or go past and try again. But doing and undoing one of them 3 pin Lucas Rists connectors with one hand is a skill that I clearly need to work on.

Graham

GrahamFountain wrote: ↑Sat Jan 09, 2021 1:02 pm Is this the right switch?



Graham

Yes!

Steve

If I can't make the spring hold the through hole LED in contact properly - seems to be more the earth than the supply - I'll get one of these then.

But the through hole LED has a shoulder. So, if I can get the right sized washer by drill and by file, even a metal one, with the LED stuck through and the washer on the LED's shoulder, the spring should hold it all tight - I may need a longer one though. But it should be possible to fix the one I have.



Graham

I put one of these cheap illuminated pull switches off ebay in while I look at fixing the light in the old switch:



It's on a lead made of a TR7 3-pin Lucas connector that fits, so I haven't modded the original. But I may have to if I hardwire a 5mm LED in the body, like I think I may have to if I can't make the spring that bears on the front of the bulb work with a LED version of a normal bulb.

This cheap switch isn't a great fit, and really wants a mounting with less gap to the card front making up - a flat plate with some holes drilled in the right spots would probably work. But there's enough of it sticking through to get hold of (might be tricky with gloves on though) and it works:



And now it lights up, I'm not so likely to leave it on and walk away. I really need either an alarm from the door switch, like the lights left on one, or a relay off the ignition in the power feed to the heater.

Why would the rear screen heater not be switched off the ignition? Just to save a relay or a higher current switch or one with more terminals?

Graham

Still trying to fix the old switch light. It turns out that while the through hole LED fits, it won't work because it's unipolar and the bulb holder in the switch is reverse powered, with earth on the end connection and live on the body.

So I'm down to protecting the face of the COB LED from the spring that holds it in, or hard-wiring a discrete LED in the bulb holder and junking the spring.

Graham

There are positive earth through hole LEDs on ebay that look like they'd fit. But rather than buy more LEDs, I've potted the bi-polarity COB LED in some transparent hot glue to protect the LED panel and the components behind if from the spring. Trimmed that to size with a heated steak knife (be okay as long as SWMBO don't find out). Seems to work okay now, so I shall put it back in the car.



So now I'm back to having a spare for the LED in the clock that I'll probably never need. Also got a spare green LED that fits the clock, but is over bright.

I'm also thinking I may make up a short 3-pin to 3-pin lead with an ignition switched relay in the feed, so I can't leave the rear screen demister on by accident.

Graham

GrahamFountain wrote: ↑Sat Jan 16, 2021 3:13 pm
And now it lights up, I'm not so likely to leave it on and walk away. I really need either an alarm from the door switch, like the lights left on one, or a relay off the ignition in the power feed to the heater.

Why would the rear screen heater not be switched off the ignition? Just to save a relay or a higher current switch or one with more terminals?

Graham

If your HRW is fed from a permanent live it's not right! All the many many Dolomites and Sprints i've seen have the HRW wired through an ignition live. Precisely so you CAN'T leave it on and flatten the battery! I don't know why ANYONE would do it any other way!

Steve

Carledo wrote: ↑Wed Jan 20, 2021 10:03 pm If your HRW is fed from a permanent live it's not right! All the many many Dolomites and Sprints i've seen have the HRW wired through an ignition live. Precisely so you CAN'T leave it on and flatten the battery! I don't know why ANYONE would do it any other way!

Steve

I take it the feed should be off the switched side of the fuse box. If it's on it's own Lucar connector, is it possible it's just got put back on the un-switched side at some point?

I think I will still look at adding in a relay, and leave the feed off the un-switched side. The problem is that the 150W fan heater should draw over 10 Amps - bet it's less then that though -, and I'm thinking of fitting a supposedly 500W one in the boot. That has two tubes for output that I'm thinking to run to vents in the already hacked-up shelf cover - got a couple of spare Herald front dash ones I think will do. That's because, while the supposedly 150 W one proved the concept, it only clears a foot wide strip.

Graham

GrahamFountain wrote: ↑Thu Jan 21, 2021 10:14 am

Carledo wrote: ↑Wed Jan 20, 2021 10:03 pm If your HRW is fed from a permanent live it's not right! All the many many Dolomites and Sprints i've seen have the HRW wired through an ignition live. Precisely so you CAN'T leave it on and flatten the battery! I don't know why ANYONE would do it any other way!

Steve

I take it the feed should be off the switched side of the fuse box. If it's on it's own Lucar connector, is it possible it's just got put back on the un-switched side at some point?

I think I will still look at adding in a relay, and leave the feed off the un-switched side. The problem is that the 150W fan heater should draw over 10 Amps - bet it's less then that though -, and I'm thinking of fitting a supposedly 500W one in the boot. That has two tubes for output that I'm thinking to run to vents in the already hacked-up shelf cover - got a couple of spare Herald front dash ones I think will do. That's because, while the supposedly 150 W one proved the concept, it only clears a foot wide strip.

Graham

500W = 41A at 12V - more at 13.8V ( 48A) ! Some heavy wiring needed and I assume you have uprated your alternator? Cold start - so battery gets a caning before you drive off so needs & recharging, lights on, main heater blower, wipers all likely on at same time. 12A lighting, 4A blower motor, 4A ignition, 4A wipers = over 24A then add your 41A for the 500W heater - 65A before you even get to recharging the battery. Do a few short winter runs and even with an 80A alternator you battery will die. Not only do you need to uprate the alternator but also the wiring to it. I would also include some sort of timer relay so that it turns off after a preset time.

How about cleaning off all the old elements and using one of these kits:

https://www.holden.co.uk/p/screen_heater_12_volt


Roger

GrahamFountain wrote: ↑Thu Jan 21, 2021 10:14 am

Carledo wrote: ↑Wed Jan 20, 2021 10:03 pm If your HRW is fed from a permanent live it's not right! All the many many Dolomites and Sprints i've seen have the HRW wired through an ignition live. Precisely so you CAN'T leave it on and flatten the battery! I don't know why ANYONE would do it any other way!

Steve

I take it the feed should be off the switched side of the fuse box. If it's on it's own Lucar connector, is it possible it's just got put back on the un-switched side at some point?

I think I will still look at adding in a relay, and leave the feed off the un-switched side. The problem is that the 150W fan heater should draw over 10 Amps - bet it's less then that though -, and I'm thinking of fitting a supposedly 500W one in the boot. That has two tubes for output that I'm thinking to run to vents in the already hacked-up shelf cover - got a couple of spare Herald front dash ones I think will do. That's because, while the supposedly 150 W one proved the concept, it only clears a foot wide strip.

Graham

My wiring diagram (>VA15000) shows the HRW having it's own dedicated terminal on the fusebox, 1 of 5 green leads so connected. My memory tells me that of those 5 greens, 2 are siamesed together on a single tag and the other 3 are singletons, however I can't say for sure WHICH 2 are siamesed, I THINK its the VS feed and rev counter/voltmeter feed but could be wrong. However it works though, the HRW is DEFINITELY fed from the fused ign live on ALL models. If you want to fit a relay (and I have no quarrel with THAT, i've done it myself) i'd keep the switching feed ign live and power the relay from a permanent source.

Dunno about the hot air blower rear demist, it's an interesting concept and may well clear the window more efficiently than the original heater element. But it will involve some unsightly plumbing and the matter of current draw, big wiring and possible bigger alternator requirement make, IMO, a good used window a more practical and cost effective proposition. A toughened HRW is a lot easier to fit (and less potentially disastrous if you get it wrong) than a laminated front screen! I recently fitted both rear AND front screens to a Sprint in less than 1/2 an hour (empty shell after colour change respray and new vinyl/headliner) and had them sealed in and mouldings in place in not much more than another 30 mins. On my own!

Steve

Well if I believed a 500W heater bought for £14 off ebay was, even at 13.8v, 500W and would drew anything like 36A (where does 48A come from?), I might be concerned. If it draws as much as 10.4A (500W/24V*12V/24V) off a nominal 12V supply I'll be very surprised - the only thing that cheap on ebay is hyperbolocks.

And I've got high capacity supply cabling in for a sub amp, i.e. for the low impedance, I was gonna fit on the back ledge but I never did. That should do nicely (the amp would probably have de-misted the back screen too).

And I do have an uprated alternator, though I forget what it is.

And all the aftermarket, stick-on demisters I've ever seen were crap. So I didn't look. They may have got better in the last 3 or 4 decades though - I hadn't thought of that. But £47.64 inc. drat & P&P seems a lot just to find out. Or is that being a bit Yorkshire.

And are you allowed to drive off, i.e. need lights and wipers, before the screens are clear?

Graham

GrahamFountain wrote: ↑Thu Jan 21, 2021 3:34 pm Well if I believed a 500W heater bought for £14 off ebay was, even at 13.8v, 500W and would drew anything like 36A (where does 48A come from?), I might be concerned. If it draws as much as 10.4A (500W/24V*12V/24V) off a nominal 12V supply I'll be very surprised - the only thing that cheap on ebay is hyperbolocks.

And I've got high capacity supply cabling in for a sub amp, i.e. for the low impedance, I was gonna fit on the back ledge but I never did. That should do nicely (the amp would probably have de-misted the back screen too).

And I do have an uprated alternator, though I forget what it is.

And all the aftermarket, stick-on demisters I've ever seen were crap. So I didn't look. They may have got better in the last 3 or 4 decades though - I hadn't thought of that. But £47.64 inc. drat & P&P seems a lot just to find out. Or is that being a bit Yorkshire.

And are you allowed to drive off, i.e. need lights and wipers, before the screens are clear?

Graham

Well, since you put it like that.......

Asssuming you HAVE a 500w draw then 36a @13.8v is correct (not that doubt you, I did the sums for my own satisfaction) and you already HAVE the cabling in place and an uprated alternator then it looks a lot easier. AND has the added bonus of hot air in the rear of the car. Not something that would normally bother me, but having spent several freezing hours trying to sleep in the back of a Sprint on the RBRR (the heater was fine and the front was toasty but the heat seemed to stop at the front seat backrests) I can see that as an advantage!

On stick on demisters, I too haven't fitted one or used one one in better than 30 years. The ones I remember from the 70s don't fill me with enthusiasm, only just better than nothing is my summation! I hadn't thought of tech improvement but how much is there? the old ones didn't work well OR last long, with the weight of the terminals dragging them off the screen and breaking the filament or the whole thing coming unstuck in a matter of weeks. So I don't consider it an option either.

Driving off before screens are clear? There is a difference between what you SHOULD do and what most folk WILL do! That's why a lot of moderns have a front screen element that clears even ice in 15 secs! The power draw on THAT must be enormous, if only short lived!

Steve