Stepper motor questions

WarGawd

Original poster
Member
Sep 2, 2012
468
Number 2 of a series of questions :smile:


I've seen many threads describing the stepper motor issues on these vehicles, and the behavior that typically distinguishes the stepper as the culprit from other possiblilities. I noticed from the stepper motor replacement article here that there is now a 3rd revision to these. I don't recall having seen any mention of that on the OS.

I have determined my oil pressure stepper is bad (doesn't always zero, sometimes pegs at upper limit), and since I can hear others ticking during operation I ordered all 6 plus 10 free guage cluster lights off an Ebay seller for $31.25 this morning with lifetime warranty.

My particular Envoy was imported to Canada from MI in '07, and from discussion with local dealer I believe the entire guage cluster would have been changed at that time (IE not just a faceplate). I had thought that would mean it had the re-designed rev 2 x25-168 steppers, and didn't really expect to need to replace mine {seems I'm wrong though}

Q2: Does anybody know the revison history of these motors to know what was changed from the original X-C5-168 to the X-25-168 to the now apparently lifetime warranted X-27-168?

Q2a: Although none of my lights is out, should I just change them all anyway as a preventitive measure?

Q2b: Is there anything else I should consider doing while I have the cluster out? Mods? Upgrades?

Thx
WarGawd
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
With my engineering curiosity, I did a total stripdown disassembly of a bad stepper once. Posted pics on the OS. There really is no way to tell what they changed if it's (as I'm guessing) a material change in the rotor, or something like an increased number of wire turns in the coils. I never Googled for any more technical details. They're cheap. Just go with the flow and swap 'em. I wouldn't touch the lamps or anything else in there. It's only like four minutes to take it out again if you need to.

stepper1.jpg


stepper2.jpg
 

NJTB

Member
Aug 27, 2012
612
Flemington, NJ
If you look at the number on the back of the new stepper motor, it should be different from the old one. Which revision it will be I have no idea.
 

WarGawd

Original poster
Member
Sep 2, 2012
468
NJTB said:
If you look at the number on the back of the new stepper motor, it should be different from the old one. Which revision it will be I have no idea.

Sorry I guess it wasn't clear - the Ebay link is for the X-27-168 steppers, so I'm pretty sure that's what they'll be. I was more curious about the timeline of the introduction of the rev 2 X-25-168's (because I expected my '07 installed gauge cluster would have those) and what it was they theoretically improved on those vs the original because they seem to have still gotten it wrong necessitating a rev 3.
 

NJTB

Member
Aug 27, 2012
612
Flemington, NJ
WarGawd said:
Sorry I guess it wasn't clear - the Ebay link is for the X-27-168 steppers, so I'm pretty sure that's what they'll be. I was more curious about the timeline of the introduction of the rev 2 X-25-168's (because I expected my '07 installed gauge cluster would have those) and what it was they theoretically improved on those vs the original because they seem to have still gotten it wrong necessitating a rev 3.

After I re-read your question, you were plenty clear, I gave you a poor answer.
Whatever the reason for 3 revisions, the fact is they are still (at least the first 2 revisions) failing. It's not a difficult job to do, so my thinking is when the stepper motor fails, replace it.
I stumbled on this list a few months ago, and while looking through the posts came across the thread on how to replace the motors. Started the job about 4:00 and was driving the car at 5:30, and the gauges worked. I looked at it as well, you bought the car, this is what you have to live with.
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
Yet another Google-quest just now, and I continue to not find any detailed technical reason for the stepper redesign. So I can't help, and the true root cause may be locked up until (perhaps) the truth comes out as the lawsuits against GM for stonewalling a recall proceed. If I was the designer and their manager, I'd be quiet. :redface:
 

WarGawd

Original poster
Member
Sep 2, 2012
468
Managed to find time to get this little project going.....wish I had done it sooner (because then I would remember where the hell I put the solder I bought!).

And I had an interesting discovery - the tach and speedo had the rev 2 X25-168 steppers, the Oil/Alt/Temp/Gas ones all had the original XC5-168's. Close examination of the back of the PCB showed no disturbance to the conformal coating used in that area, so I'm 95% sure this board has never been re-worked with rev 2 steppers for just the tach & speedo. SOoooooo I'm guessing my swapped out gauge cluster from back in '07 when it was imported was one of the early adopters of the new stepppers and the Eng. dept hadn't gotten around to updating the part #'s spec'd for the other locations. Pics later, after I find somewhere to buy some more solder early on a Sat morning. :hissyfit:
 

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