JPTL

The ! warning light and belt tension warning comes on 4 or 5 minutes after driving, regardless of the type of driving.
We did a full t/b & w/p job with a tensioner rebuild about 30 (street/track) driving hours ago. Belt was retensioned last season.
For good measure, I just checked the tension of the belt and it was at the far end of the notch on the Kemph tool...so certainly not loose. I filled the tensioner while I was in there.
The thru-case connector doesn't have a snug fit, and I'm suspecting that's the culprit.
Because the light consistently comes on about 4 minutes in, and I know the belt isn't loose, I'm thinking it's not a mechanical issue, but an electric one.
I remember someone on the list mentioning that they also had a sloppy connector that was causing false tension readings. Anyone have luck replacing/fixing a worn connector?
Any thoughts on what else it could be?

Mrmerlin

well start with the simple stuff first I would fix any loose connections first

Imo000

Ground the connector from that plugs into the belt cover and see if the problem goes away. If it does, the connection or the wire on the other side of the belt cover is the problem.

JPTL

I'm confused. Woudn't be the other way around?
If after grounding the thru-case connector the light doesn't come on, aren't I confirming that the circuit is good...and since I'm taking the tensioner out of the equation, the light not coming back on doesn't rule out a mechanical issue with the tensioner?
If the light comes back on after grounding the connector, then I know that there's an issue in the circuit beyond the thru-case connector.
..right?

James Bailey

the tension warning circuit looks for a ground ( after a few minute delay) if it sees a ground it thinks the tensioner is touching the arm and all is good. Which is how many " mechanics " defeated the warning by just grounding the wire to the engine.....

zekgb

The two main culprits of false alarms on the tensioner side of the circuit are a missing washer that sits atop the spring on the tensioner and incorrect orientation of the spade on the tensioner arm which causes it to rub against the center cover.

StratfordShark

You've confirmed belt tension is good, so the warning is false caused by electrical problem. Grounding the connector isolates the problem to the wire from the spade terminal running down to tensioner nose, or the connection to the spade terminal.

I think if the washer on tensioner nose is missing, then the tension has to drop below the normal lower limit for warning to be triggered, which is not the fault you describe but would reduce usefulness of warning system.

JPTL

The only thing that keeps bouncing around in my head is that the tensioner isn't working for some reason. It's making me nervous to drive it. I'm registered for a track day on the 10th and definitely want the tension warning system to be working properly.
Considering that the belt is definitely at the high limit of tension, if the circuit were good but the tensioner weren't working at all for some reason, could the tension warning still pop up?
Given that the light appears consistently within 4-7 minutes from startup regardless of driving conditions (revs, rpm, heat, etc) I'm focused on something going on with the circuit/connections.
I haven't had a chance to get into the connections and ground the connector as a test, but that's the next item of business.

Wisconsin Joe

Keep in mind that the "tensioner working" means that it's relaxing a bit as it heats up. The Bellville washers flatten out a bit with increased heat, and that keeps the belt from getting too tight as the block expands due to heat.

There's no "active" adjustment at all in the factory tensioner. Just loosening up a bit for heat.

dr bob

JP --

You can do a lot of tensioner switch troubleshooting with an Ohm meter (DMM function). Pull the connection from the cover, and with that wire lifted test the wiring from the cover connection through the tensioner for continuity to ground. Should be zero Ohms or really close to zero. If it doesn't show continuity, the problem is in the tensioner electrical. Can easily be a broken conductor between the cover and the ring the wire connects to on the end of the piston. With the upper covers off, you can reach in with the meter probe to find what's grounded and what isn't, and see where the connection is lost. Doing it this way lets you work on the engine cold, and no need to wait five minutes after starting to see if your fix is good.

John Speake

The approx. 4 minute delay is built into the system. This is because the belt is quite loose until the engine warms up. So never start your 928 from cold and rev the engine to impress anyone - not that any of you would do such a thing...

So the delay will not be affected by the way you drive in that initial period.

worf928

This-^

JPTL

I appreciate the input. It's always good to learn as much about an important component as possible before attempting to fix it. The delay in the belt tension warning system is important to understand, particularly when troubleshooting the tensioning system. Thanks for the insight.

The thru-case connector



...falls right out of the hole in the case b/c nothing is holding it in. I'm thinking that the contact inside the cap is shot.

Is it the washer or contact that holds it in? I need to fix this even if it's not the culprit - which I think it is. (thanks for the photos, Carl)
What's involved in replacing this little connector? Does it need to be soldered into the line a few inches up the harness, or is there a snap connector?
In this post, Carl Fausett is suggesting that replacing this end isn't as simple as plug & play...unless it's this part: 999 659 001 40

Mrmerlin

you can buy a new short wire junction and grommet
this plugs into the center timing cover.
then your O ringed plug fits into it.
Roger got me one

Imo000

I yet to see a case where anything happened to the belt when a cold engine was revved. I think this is an internet myth.