The Morbidmobile Blog

[Laird Scooby]

Originally Posted by Stephen Edwin

- no extra switches to turn lights off if the tailgate is moved!"

implicitly

Where in the construction and use regs? They are such a minefield. Someone writing the regs. must have tried to anticipate so many permutations. EEK

As i said, no extra switches! Feel free to have a look through the C&U, i studied them best part of 30 years ago and have tried to keep myself current apropos HID/LED lighting and the various permutations thereof but i'm not going to go through them all again when all that needs to be known is there should be no other switch to control the obligatory rear lights other than the dashboard main lighting switch, with the possible exception of the cut-out previously mentioned for the rear fogs.

[TomSaintJames]

As far as the mystery switch goes, what I thought there might be was a courtesy light switch (like found in the passenger doors) that turned on the interior lights when the tailgate is opened, and given the general bodgery of the electrics on the tailgate it had gone kaput and was affecting the other lights.

The whole tailgate - from below the lights upwards opens, leaving a nice low and wide loading area at top-of-bumper level.

I will check the fuse, is there anything else on that fuse circuit or just the fogs? I'm sure it'll be in the HBOL when I get home if no-one knows off the top of their heads!

The wiring for these lights comes through the bodywork at the hinge area, they appear to be inside a protective sheath which is cable tied to the body hinge bracket, even to my eye the cable tie is tight, but I cannot see that the angle of the tailgate could have any affect on the wires, as the body hinge bracket is static - perhaps it's more of flex/stretch of the wires? I haven't seen any of the bumper light wiring either, so a general fiddle (with pictures) shall have to be done at the weekend.

I'm also not sure of the earthing situation, as the tailgate is fiberglass (I think), it must earth elsewhere on the body. There are quite a few wires with spade connectors attached to one of the light cluster mounting bolts on each side, but again due to the mess of wires I haven;t really looked very hard at it.

Thanks,
Tom

[Stephen Edwin]

Originally Posted by Laird Scooby

As i said, no extra switches! Feel free to have a look through the C&U, i studied them best part of 30 years ago and have tried to keep myself current apropos HID/LED lighting and the various permutations thereof but i'm not going to go through them all again when all that needs to be known is there should be no other switch to control the obligatory rear lights other than the dashboard main lighting switch, with the possible exception of the cut-out previously mentioned for the rear fogs.

As is part of what you said indeed.

I am not convinced.... but that's water under the bridge.

In case I ever need to rely on the point, it would be jolly useful if one could see the actual wording of the regulations. I try to always learn as best I can but I can put the matter aside as something I'm unlikely to need to know.

David. Re learnng as best I can. My ears pick up when I hear law mentioned. I do tend to ask questions to try to learn. Cushti.

[Stephen Edwin]

Originally Posted by TomSaintJames

As far as the mystery switch goes, what I thought there might be was a courtesy light switch (like found in the passenger doors) that turned on the interior lights when the tailgate is opened, and given the general bodgery of the electrics on the tailgate it had gone kaput and was affecting the other lights.

The whole tailgate - from below the lights upwards opens, leaving a nice low and wide loading area at top-of-bumper level.

I will check the fuse, is there anything else on that fuse circuit or just the fogs? I'm sure it'll be in the HBOL when I get home if no-one knows off the top of their heads!

The wiring for these lights comes through the bodywork at the hinge area, they appear to be inside a protective sheath which is cable tied to the body hinge bracket, even to my eye the cable tie is tight, but I cannot see that the angle of the tailgate could have any affect on the wires, as the body hinge bracket is static - perhaps it's more of flex/stretch of the wires? I haven't seen any of the bumper light wiring either, so a general fiddle (with pictures) shall have to be done at the weekend.

I'm also not sure of the earthing situation, as the tailgate is fiberglass (I think), it must earth elsewhere on the body. There are quite a few wires with spade connectors attached to one of the light cluster mounting bolts on each side, but again due to the mess of wires I haven;t really looked very hard at it.

Thanks,
Tom

It sounds as if quite some perceptive investigation will be necessary. Good luck. You'll get it sorted.

I asked about the wires reaching the tailgate because that is a regular cause of difficulties on 240 estates. Those 240 tailgate wires including earth wire(s) go "through" the hinges and the wires fail. The wires going is it alongside your hinges would be well worth investigating.

It sounds as if there is a mystery switch. Time may tell or it might remain a mystery. If found I would be tempted to remove it from circuit, have those lights wired without that switch. The switch is something else that could fail and is not really necessary in my opinion.

Odd custom wiring might take a little time to sort out. All will be well.

[Laird Scooby]

The big problem is Volvo changed the fuse location on the early 740s Tom and the HBoF doesn't list the 1988 model fuses - do you not have a Volvo handbook for it?



That shows where the fusebox is and when you pull the ashtray holder out (by pressing or lifting the flap at the outer edge then pulling) you should find the fuses listed on the back.

I've found two references, one up to 1985, the other 85/86 and the first shows the fuse as being fuse #7, second as #16 so you'll need to look at that for the information you need.
Also on the 760 (which is similar), on early cars it refers to a rear fog relay - whether that was ever fitted or not i don't know but i did look at a diagram for a 1990 (think it was 1990) recently and there was no relay for the rear fogs.

Don't forget that yours is massively (in more ways than one!) modified from a standard saloon, unless you can find a VIN number that we can work out the model year from we're shooting in the dark at black bears hiding in caves because of Volvo continually changing things and the fact it has been changed from standard!

[Stephen Edwin]

Originally Posted by Laird Scooby

..... we're shooting in the dark at black bears hiding in caves because of Volvo continually changing things and the fact it has been changed from standard!

Very true.

Now is a good time to document whatever is found, for future reference.

Whilst investigating the fuses, maybe change them all for either fuses that glow when they fail, or those miniature circuit breakers with reset buttons?

[Laird Scooby]

Originally Posted by Stephen Edwin

Very true.

Now is a good time to document whatever is found, for future reference.

Whilst investigating the fuses, maybe change them all for either fuses that glow when they fail, or those miniature circuit breakers with reset buttons?

Out of the two choices on those replacement fuses, the resettable ones would be a better option. Two reasons, first, once they trip the button pops out so they can be seen to be tripped whether power is on the circuit or not and secondly, once the "glow-when-they-blow" fuses blow, they are dead - as dead as previous back seat drivers of the Morbidmobile and to that end, dead money as well.

Also the glow-when-they-blow type won't light up if the power isn't present on the circuit - for example an ignition fed circuit unless that circuit is made live. Nice gimmick, but that's all they are sadly.

[Stephen Edwin]

Originally Posted by Laird Scooby

Out of the two choices on those replacement fuses, the resettable ones would be a better option. Two reasons, first, once they trip the button pops out so they can be seen to be tripped whether power is on the circuit or not and secondly, once the "glow-when-they-blow" fuses blow, they are dead - as dead as previous back seat drivers of the Morbidmobile and to that end, dead money as well.

Also the glow-when-they-blow type won't light up if the power isn't present on the circuit - for example an ignition fed circuit unless that circuit is made live. Nice gimmick, but that's all they are sadly.

Choice init.

I tend toward the circuit breakers. With at least one spare of each value in case one fails.

Another advantage, circuit breakers MIGHT switch off more quickly than a blade fuse blows, giving quicker protection.

I find household circuit breakers are not just convenient. They are reputed to trip very quickly when necessary. Maybe the same applies to car type circuit breakers.

But re glow-blow they are not without advantage over ordinary fuses, and I have learnt to switch on the ignition when required.

There might be a cost compromise to be done for some of us. And a glow-blow fuse can be spotted very quickly. Cushti. If I had a blade fuse board in the jam jar, I might use mainly glow-blow as an advantage over ordinary fuses, with circuit breakers for any especially important or likely to blow circuits. But as it is academic for me at the moment, I can say that I would splash the cash on circuit breakers.

[Laird Scooby]

I'd stick with the original blade fuses and invest a mind-blowing £2.38 on one of these :

https://www.ebay.co.uk/itm/CAR-AUTO-...e/113216252767



Easy to use to test a blown fuse, clip the croc clip onto a known good earth then probe the ends of the blade fuse, usually there are contacts in the ends of the fuse that can be probed :



Touch the probe onto each end in turn, if it's blown only one end will light the test lamp - cheap and easy. Job done!

[Stephen Edwin]

Indeed. Or cheaper, either use the olde but otherwise almost identical one I've got, or solder one up with scrap box bits.

But nice blow-glow fuses or circuit breakers would be nifty, especially because things tend to happen when one is several counties away from home in freezing weather with heavy traffic driven by impatient drivers .... and one just wants to know the answer and get home A S A P !!!