Throttle Pot

[landrovernuts]

Hello All

My hotwire TPS is knackered and I am just wandering if anyone knows of an alternative, or good pattern part that will fit? Just goes against the grain to pay £180 for a genuine item from LR when it is only a variable resistor.

Any help appreciated.

Toby

[kiwicar]

I'm pretty sure Ramon has an alternative on his website.
have a search on his profile.
Best regards
Mike

[DaveEFI]

I'm pretty sure Ramon has an alternative on his website.
have a search on his profile.
Best regards
Mike

The hotwire uses a different design TPS from the flapper and I've a feeling the RS Components sourced Vishay rotary position sensor used to replace that isn't suitable.
But there is a data sheet on the RS site which gives electrical and mechanical spec. The RS part number is 319-310

[landrovernuts]

Thanks for the replies.

Just a few questions! I know the pots for flapper and hotwire are different (and later hotwire have a different plug) but are they electrically different, or is it mechanically different. Just wandered as the ones that RS have in stock are only £30 and we have an RS account at work, just wandered if it is possible to adapt one of these to fit the hotwire system?

Toby

[ramon alban]

are they electrically different, or is it mechanically different. Just wandered as the ones that RS have in stock are only £30 and we have an RS account at work, just wandered if it is possible to adapt one of these to fit the hotwire system?

Hello Toby, hopefully you found the TPS essay on my web pages.

Actually the world is full of them.

http://shop.ebay.co.uk/i.html?_nkw=Thro ... m270.l1313

mostly sharing similar characteristics.

5k ohms because early bosch/lucas systems used by rover specified it thus and as others fitted that system to other cars, the value became bog standard, I suppose.

90 degrees deflection to match the obvious throttle plate rotation limits.

As it happens, the RS unit is 106 degrees but still works fine on the flapper system, and I cant see why it would not do likewise on HW.

By and large, the TPS is only a performance enhancing component telling the ECU to enrich mixture during acceleration and at full load. The rest of the time it is mostly benign, - at least on the flapper.

Worth noting, the flapper Efi works OK with the TPS disconnected, just lacking the enrichment functions, making it a bit lack-lustre.

So with commonality as described, this just leaves adaptation, which purely a mechanical thing plus simple rewiring.

For the RS unit you can see how it was done on my web pages.

You could compare that design to your actual engine fixing position and see if it might work or be modified accordingly.

A modicum of workshop skill is required, of course..

[DaveEFI]

Thanks for the replies.

Just a few questions! I know the pots for flapper and hotwire are different (and later hotwire have a different plug) but are they electrically different, or is it mechanically different. Just wandered as the ones that RS have in stock are only £30 and we have an RS account at work, just wandered if it is possible to adapt one of these to fit the hotwire system?

Toby

They've gone up a lot in price recently. I bought a few at just over 20 quid earlier this year. Exchange rate? BTW, anyone with a credit card can buy from RS unlike years ago. You could also try a search

Can you not measure your one and see if the RS one is a suitable replacement? They do look similar.

[landrovernuts]

Thanks again for the replies. I have been to Bearmach and there replacement one is £158 and that is pattern!
Think I will go down the RS route and adapt, as I am an Engineer and have access to a workshop. I will look at Ramons modification as soon as I can (I am at work at the moment and being watched!)
As for the function of the TPS yes could not agree with you more and with it however I have an anoying hesitation just when you put your foot down now. I have measured the resistance and it is a contant 192 ohms even when moving the pot spindle.

Thanks for your help

Toby

[DaveEFI]

Thanks again for the replies. I have been to Bearmach and there replacement one is £158 and that is pattern!
Think I will go down the RS route and adapt, as I am an Engineer and have access to a workshop. I will look at Ramons modification as soon as I can (I am at work at the moment and being watched!)
As for the function of the TPS yes could not agree with you more and with it however I have an anoying hesitation just when you put your foot down now. I have measured the resistance and it is a contant 192 ohms even when moving the pot spindle.

Thanks for your help

Toby

The hotwire pot I've seen is totally different to the flapper one, so any details for the flapper substitute are not likely to help much. Unless yours looks the same as the flapper one, in which case it's likely to be the same.

Have you looked at the spec sheet on the RS site? As I said it gives dimensions etc.

As regards the constant 192 ohms, I've never come across a pot fault that could give that. Could you disconnect it, and measure it then? If the wiring is the same as the flapper one you need to measure across green and yellow to get the track resistance which should be around 5000 ohms.
The wiper is the the red wire and from that to green should vary from about zero to 5000 ohms as you turn it. But those figures are for the flapper type.

[landrovernuts]

Hello Dave

The pot is sitting on the kitchen top (currently getting grief about this) and measures a constant 192 ohms between the green and red even with twisting the spindle and 5.66 Kohm between green and yellow. So total resistance is not far out, but green to red is!

I have to say my pot looks like a flapper one, it has a Lucas part number of 84925A. The RR manual lists 3 different part numbers for TPS, 2 for hotwire (because of plug change) and one for flapper. I have to be honest apart from the plug change they all look the same, but this is probably just how they show them in the parts manual. Can anyone show with some pictures how they differ?

For £30 and some of my time, I will try and adapt an RS one.

Thanks for your help

Toby

[DaveEFI]

Hello Dave

The pot is sitting on the kitchen top (currently getting grief about this) and measures a constant 192 ohms between the green and red even with twisting the spindle and 5.66 Kohm between green and yellow. So total resistance is not far out, but green to red is!

I have to say my pot looks like a flapper one, it has a Lucas part number of 84925A. The RR manual lists 3 different part numbers for TPS, 2 for hotwire (because of plug change) and one for flapper. I have to be honest apart from the plug change they all look the same, but this is probably just how they show them in the parts manual. Can anyone show with some pictures how they differ?

For £30 and some of my time, I will try and adapt an RS one.

Thanks for your help

Toby

I thought ones on later hotwire systems looked similar to the RS one.

If you have the flapper type, they can sometimes be fixed. Have a look on Ramon's site for details. It involves opening them up and moving the wiper across to an unworn part of the track. But so saying, that constant reading you have means something else may have failed.

I made up some ally discs to adapt the RS pot to the flapper fixing. Think I may still have one. £15 including postage.

[landrovernuts]

Hello Dave

I have sent you a PM!

Toby

[landrovernuts]

Hello Dave

Do you still have that ally disc conversion? I sent you a PM as I am interested.

Toby