Here goes... I just bought a used transducer for my 81 (the transducer is from an 82 and I'm just using it until I rebuild my own). I want to inspect the new unit thoroughly and maybe even grease it etc. Has anyone had any experiences taking these apart? I figure if I can get through this, I'l be ready to tackle my factory unit and pass the 82 on to someone who can use it.

I did check the Service manual but they only show how to test the unit electrically i.e. with an ohm meter. The Assembly manual shows only wiring hookup. I can't find an IPB anywhere so I can see the insides or get an idea how to disassemble it.

Any help would be gretly appreciated

STW!

Platato

 

I once worked at a shop that repaired them.

It took special guages, a vacuum pump, and a column of mercury to repair and adjust them properly.

 

Try:
http://www.nottingham.ac.uk/~eaztl1/...leshooting.htm

Roger

 

While Roger's post is pretty good, I'm with Mike. The insides of this beast are not for the faint hearted. I think that it's beyond the scope of the home mechanic for all but the simplest transducer repair.

My .02

 

Hmmmmm

I'm not sure what to think yet. I would really like to learn how to repair these (mostly out of fun & curiosity). Rogers' link sure made it sound like the physical assembly/re-assembly is pretty straight forward but you guys got me wondering.

My shop manual and the link do a good job discussing the correct electrical testing/troubleshooting. That part seems pretty reasonable.

Can anyone explain what the purpose of or proceedure of applying vacuum to the rebuild process for calibration? Is this something that would come in when replacing the cover and deciding it's exact position?

This is a very interesting tech issue as there just isn't much information out there on transducers, It's like a little "mystery box". I look forward to some more discussion on this topic.

STW & Thanks!

Platato

 

I wish I could, but (back then) CC repair was a totally different department. I never got indepth with what exactly they did - other than watching them do it from time-2-time.

I was upstaris repairing tachometers, engine computers, and car radios.

I must say they they staffed that department with recent high-school graduates... so it must not of taken a lot of ability. But the special guages (feeler-type) and a vacuum pump, and the column of mercury were used on each unit repaired.

 

Gotta bump it since I'm trying to figure all this out!

so Mike, do you still play with stereos I might have an ETR or two for you to look at

STW!

Platato

 

There doesn't seem to be a lot of info out there about testing and fixing these things - I was just about to link you to my pages on this, but someone's beaten me to it! Oh well, at least those pages are being read

I have to say, provided the bulk of the internal parts are serviceable, there's no reason why cleaning and reassembly wouldn't work just fine. The internals of this thing are just like a speedo, it works in exactly the same manner.
Other than replacing the spring inside, or changing the diameter of the orifice, (neither of those is likely) there's little in the way of "calibration" needed.
As for the "rotatable" casing, the position of this determines the speed at which the device becomes live - supposed to only work above 30mph or similar, but "tuning" is possible by rotating the case...

Did you get the other link from my page? There's better detail on the insides of the device at
cruise transducer disassembly

Good luck, I bet you can overcome most problems with your old unit - even if you have to just swap out the internals from a "working" one.

 

Forgot to mention also that the set speed error is adjustable by turning the orifice tube in or out of the body...But this adjustment is done after the unit is reinstalled in the car.

Platato - have you had yours apart yet? Do you know what the problem is??

 

Yep, I repaired Delco's Electronically Tuned Radio... when they were still under warranty !!!!!!

But that was 25 years ago. But the most common audio problems were the output IC's. They originally had DM-59's - then went to the DM-82 ????? (if i remember correctly).

It's been too long - no schematics - and little memory

 

Your site on the transducer is really, really good! It's great you took the time to create the pages and you should be commended!

The new (old) transducer seems to have some resistance when you try to spin the shaft (small one) by hand. I really have no idea how firm this is suppose to feel but my guess is that it should spin very freely? I was wondering if this could be fixed by taking it apart, cleaning it & adding some lube. It feels like there is some play & then it gets firm (maybe it's the spring inside I feel and it's suppose to feel this way? I did pull the cover. Everything was intact and unbroken. Also, what are the most common problems with these units? I haven't pulled the stock unit yet because I figured I'd go through the new (old) one and use it as a guinea pig to learn all I need to know before I get into my factory and dare I say NCRS required part.

I don't know much about these magical little gadgets but for some reason I'm intrigued by them and would like to everything there is to know about them. This thread & your site have definitely been helpful with this subject. I'm looking forward to learning more including if there's a way to rebuild the...Ummmm I'm drawing a blank, brainfart! You know the diaphram I squeeze to increase engine RPM's while working under the hood or after start up when i'm trying to get the RPM's to drop....Aw hell, looks like I'l have to scrape the fuzz out from between my ears & then edit


Anyway, I'm looking forward to learning more so keep the good info coming guys

STW!

Platato

 

Thanks very much - it was totaly motivated by the lack of info out there, and also the fact that, like yourself, I was a bit fascinated by these crazy little devices...

I'll be happy to try and help you in what ever way I can, so let's start with trying to answer your first questions..

As for the free movement of the gearbox, yes, it should move fairly smoothly, an certainly without the tight spot you mention. But there should be a little resistance, because one of the gears is attached to the magnetic disc, which is just like a tiny flywheel. I'd say that if it's all working "right", you should be able to spin the input shaft and expect it to carry on spinning for at least a few revs after you let it go. Pick up my refurbing page from picture 11, and it shows taking the gearbox apart and lubricating.
When you put it all back together, don't press the magnetic disc back in too far or it will gall on the gearbox wall..
If you find any of the bushes are shot, I'm sure a decent machine shop could make you new ones.

As for common problems, I'd say from taking mine apart that one of the most important things to look for is a clean and smooth orifice tube (!) In fact dirt is probably the biggest killer in these devices - they're easily as delicate as your speedo, yet sit in the engine bay collecting crap all day. There's not really much to "wear out" in them (perhaps the two brass bushes and the front clutch bearing - all perfectly fixable with access to a machine shop)

Your diaphragm is called the throttle servo... Now, repairing that - good question! If it's sprung a leak, then I guess you could feasibly repair it with a bit of strong rubber glue. It seems it's held together with that big metal band that runs around it. To remove that you'd need to cut it, I imagine. Then to replace it, perhaps some solder would hold the cut back together. Depends on how desperate you are to keep the original one, or if you can find a good one from a donor car.


I'm sure if all the transducer internal parts appear to be present and correct, then it's very likely to just be in need of a good clean to eliminate internal vacuum leaks and make for smooth operation.

Do make sure you keep us posted with your progress - if you can ask the questions, I can try and provide you with the answers!
I've probably got some questions for you too, just can't think of them at the moment!

Cheers!
Theo

 

 

Have 78 vette. My transducer surges.
By your post, is there any chance of me fixing it in my garage??? Thanks

 

its been 10 yrs. since this was active. Mike is still around, pm him..