Potometer issue. My '87 V12 throttle stand potometer (potameter?) is not returning to stop easily. It seems to stick slightly. It definitely is not springy like it should be. WD40 did not help the situation appreciably. I have a replacement from my '88 H&E parts car and plan to swap them today.

My question is 'Is the '87 edition toast or can it be serviced." I am guessing they are pricey to replace.

Thanks.

 

Pricey to replace and the potentiometer may have been destroyed by other issues, these must be eliminated first, the part number for the potentiometer on an 87 HE is EAC2670, don't expect to buy one new for less than £100 and if you find one for less buy two and let me know where you found . Don't waste time on the conversions that are available - they are expensive and the potentiometer on those is even more expensive.

I initially condemned my own position sensor and that wasn't the problem at all - it was the spindle driving it and play in the bushings through which it ran allowing side to side movement - I could not get a consistent idle position voltage as a result.

The microswitch under mine was also broken up - cooked and brittle basically. The return spring on the pedestal tower is pretty strong, I'd be surprised if it was a dry bushing causing the sticking, if you're going to use a spare make sure to adjust and check everything appropriately or you may not gain the results anticipated. There are bushes in the cable support plate to support the spindle but there is no part number for them.

Guess what I'm saying is that there are numerous problems that can be affecting you, there are copious adjustments in the linkages that must all be sorted as part of any work on the tower / pedestal.

Take the linkages off the tower, remove the throttle cable and associated switch and then see how well it moves. How easily does it rotate and return to the stops with the linkages off ? how much can you rock the tower in its bushings any movement will be transferred to the potentiometer and make it difficult to impossible to adjust correctly.

There are many many places to adjust on these things, all of which provide an opportunity to mess things up, my recommendation is to start with those. Be patient they are a real challenge to do sometimes.

I've made a lower spindle support and isolator that uses roller skate bearing to stop lateral movement and it works well for what it is worth.

 

Thanks. All makes sense to me.

I have taken the unit off the throttle tower and removed the micro switch and the unit is still 'sticky.'

The '88 parts car unit works fine, very springy, so looks like I'll go with that until proven otherwise.

Last question. On the underside of the unit are three screws going thru elongated holes holding the unit tight to the base. It appears this allows for the unit to be adjusted by rotating it a bit left or right and then tightening the screws. What exactly is being adjusted by twisting it left or right?

 

You're adjusting the voltage-at-idle setting, which should be .32-.36 volts. A bit fussy to do, but entirely doable. When you tighten the screws the setting always changes a smidge. And you'll need a voltmeter.

Cheers
DD

 

Here ya go, I reckon its in the archives, and part of the Sticky at the top, but just because.

I would STRONGLY suggest lubing the centre shaft of that capstan BEFORE fitting it. A few drops of Synthetic ATF will last about 5 years. This MUST be done with the TPS removed, or all hell will break loose.

 

Apologies for a slight thread detour, but WD40 will actually make the situation worse over time. Contrary to conventional wisdom, and WD40 marketing, the ONLY thing WD40 is good for is its original purpose -- water displacement on aluminum surfaces.

The lubricant properties of WD-40 doesn't come from the substance itself, but the petroleum distillates used to dissolve/suspend the displacement ingredients. The distillates evaporate fairly rapidly, and the film that is left behind attracts dust like a magnet. When used in things like the potentiometer or locks, it might work for a short while, but a gummy mess will soon make things worse.

IIRC, Popular Mechanics did an extensive test of WD40 for all the claimed uses, and didn't recommend it for anything other than its water displacement origins. Having suffered from making the mistake of using it on a car door lock and almost ruining it, I kind of cringe whenever I see someone post about it. I used to go through big cans of it, but now I don't even buy it.