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light bars on bikeracks for small cars


cat-i
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Last weekend on the way to Mankele I discovered a very noticable power decrease when driving up hills with the car's lights are on. Switch lights off, car goes. Switched lights off, car won't go.

 

I took the Micra to the Micra-shop; they discovered that the power-reduction does not happen when the Thule lightbar (model 976)is unplugged.

 

Their explanation:

My micra (and all other small cars) was not designed to pull things, so the wiring does not have feedback-protection from single-contact light units. The single-contact lightbar feeds back and interferes with the ABS pump. This could damage the abs pump (among other things). Bigger cars dont have this problem, as they have built-in feedback-protection.

 

My questions:

- Surely there are other small cars that carry bicycles around - has anyone else experienced this with a thule light bar on a small car?

 

- The electrician said any 'double contact light unit' would work fine. What brand of lightbar would be plug 'n play, i.e. which light bar can i buy off the shelve, plug in, and it will work?

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hmm something sounds fishy Cat. :unsure:

 

Only way i can test is

 

- put my thule lightbar on another micra (or any other small car) and see if it does the same. Anyone with a micra who wants to borrow my lightbar for a while?

 

- put a different lightbar on my car and see if it does the same. Anyone with a lightbar that i could borrow for the weekend?

 

 

or if i can find other people with similar experiences?

Edited by cat-i
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Put a volt meter on the battery and see what happens when you put the light bar on - if it drops alot you know the alternater is taking strain so then the engine will take strain to try - or something like that.

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Put a volt meter on the battery and see what happens when you put the light bar on - if it drops alot you know the alternater is taking strain so then the engine will take strain to try - or something like that.

 

 

the guy at the shop said the lights are feeding resistance back to the car, activating the abs brakes pump (or something like that) .... small cars weren't designed to tow, so they have no protection.

 

I tried to google the issue, but don't really know what to google for ... but if what he says is true, then other small cars should have the same issue with this specific thule lightbar, not?

 

i'll try the battery thing - have a friend that should have a voltmeter so at least that's something i can try - thx :)

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Cat, did the car come with a tow bar and or jack for the light plug?

 

I had it installed when i bought the car - e.i. when i collected the new car from the shopfloor, it had a towbar on - but i had to ask for it and they had it done somewhere (e.i. not from the factory)

 

At that stage i didnt need the light-fitting, just the towbar itself. Now i drive more often after dark with the bike on ... but it's years later so i don't know if it was like this since forever.

 

I did have a different thule lightbar earlier, and can't remember having problems with it.

 

The car was at the shop last week to sort out an issue that i had with one of the headlights dying every 2 months or so - so there was recent work on the electrical system. The electrician that worked on the car today said for R900 he could convert the lightbar to 'double-contact' ..... but i do not want to spend the money only for them to afterwards realise that that wasn't the problem. If i can find someone else who had this issue before, then at least i'll know that the electrician wasn't just guessing.

 

I cant think that Thule could sell lightbars that would be a problem on (all?) small cars, though - it doesn't make sense??

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If Nissan had the tow bar put on for you when u brought it new then i would say that the the car should not lose power if it has lights on.

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Last weekend on the way to Mankele I discovered a very noticable power decrease when driving up hills with the car's lights are on. Switch lights off, car goes. Switched lights off, car won't go.

 

I took the Micra to the Micra-shop; they discovered that the power-reduction does not happen when the Thule lightbar (model 976)is unplugged.

 

Their explanation:

My micra (and all other small cars) was not designed to pull things, so the wiring does not have feedback-protection from single-contact light units. The single-contact lightbar feeds back and interferes with the ABS pump. This could damage the abs pump (among other things). Bigger cars dont have this problem, as they have built-in feedback-protection.

 

My questions:

- Surely there are other small cars that carry bicycles around - has anyone else experienced this with a thule light bar on a small car?

 

- The electrician said any 'double contact light unit' would work fine. What brand of lightbar would be plug 'n play, i.e. which light bar can i buy off the shelve, plug in, and it will work?

 

 

How come no one explained this to you when you asked for a towbar to be attached? What rack are you using that requires you to have a lightbar? I would go back to Nissan.

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This seriously sounds like a situation in need of an expert second opinion from another reputable auto electrician. My monitor smelled like BS while I was reading the mechanics' explanation of the problem.

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This seriously sounds like a situation in need of an expert second opinion from another reputable auto electrician. My monitor smelled like BS while I was reading the mechanics' explanation of the problem.

My montior keep going dull as i had t windows open and its only made to view one , not swap between 2. Some type of feed back :P

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How come no one explained this to you when you asked for a towbar to be attached? What rack are you using that requires you to have a lightbar? I would go back to Nissan.

 

 

Thx Caerus - will go back there when i have examples of other cars not doing the same - for the time being i have nothing but their word :(

 

It's a thule ride-on. I guess I could drive around without the lightbar (i have been for a while) - but the rack makes the car quite a bit longer - probably 1 1/2 metres. After dark i'd like other cars to know there's something between my car's taillights and their front bumpers.

 

Saturday at the Jacaranda-ride I searched for other small cars with ride-on racks, but I could only see hanging racks (and often the type that don't need a towbar) - so I guess finding other small cars with Thule bikeracks & lightbars won't be as easy as i thought. I'll keep looking though.

 

In the mean time, I'll contact Thule and find out if they'd heard about this before.

 

thx for the feedback :)

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thx agteros.

it's the light cage that's single-contact and should have been double - not the connector :(

Got feedback from Thule - they said to bring the lightbar (and the car) so that they can investigate & hopefully fix.

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  • 3 weeks later...

Some feedback:

seems like it *was* the lightbar.

 

Thule gave me another one to try for a week, and haven't had problems with it. So finally i have a working lightbar :clap:

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