Big Dave

Okay.....so I'm 1/2 way through a timing belt water/pump job and everything is going well. The belt is now fuly exposed and appears to be in great shape.

HOWEVER. Someone, either a PO or a mechanic, installed a splice onto the ground wire for the tensioner than attaches to the center timing belt cover, effectively causing an "always grounded" effect which I assume would prevent my warning light from ever being activated. The splice is now removed, so I assume the tensioner's warning is back to it's normal wiring configuration.

We (Ell is being a great guy and doing this project with me) checked the current belt's tension and it's perfect.

What we can't figure out is how to test the tensioner warning to determine whether it is operating correctly. The battery is currently disconnected.

Can one of you tell us how to test the unit with a volt meter to make sure it's functioning properly?

Thanks in advance......I've dodged a bullet now that I know that my warning light would never have come on. <img border="0" title="" alt="[Eek!]" src="eek.gif" /> <img border="0" title="" alt="[Eek!]" src="eek.gif" /> <img border="0" title="" alt="[Eek!]" src="eek.gif" />

ViribusUnits

There is a spring that trys to push the arm away from the tensioner rod.

If the tension is correct, the spring is compressed, and the contacts are connected. It's grounded, and there's no light.

If the tension is loose, the spring expands, and the contacts come apart, the grounding goes away, and you get a light.

There is no light for an overly tense condition.

For a diagram, try Tony's 928 repair tips site, here

<a href="http://members.rennlist.com/v1uhoh/timing.htm" target="_blank">http://members.rennlist.com/v1uhoh/timing.htm</a>

Good luck.

btw, has anyone tryed to retofit the tension idoit light to an older 928? Seems to me that that would be a nice thing to have.

MichaelR

Dave, did you and Ell figure out a way to test the tension warning light?

I've been working on mine, and thought that removing the wire/plug from the cover (thus breaking the ground connection) would cause the warning light to come in after three minutes. But no warning light. Now I have to start searching for potential ground sources.

BrianG

Don't forget to check the bulb, at the pre-start ignition switch position. Hate to see you cleaning all those grounding points for nothing!! <img border="0" alt="[hiha]" title="" src="graemlins/roflmao.gif" />

dr bob

Dave--

You can use an ohm meter or a continuity tester to verify the switch. Set your meter to ohms, connect one meter lead to engine ground and the other to the wire from the tensioner switch. With tension on the belt, the circuit should show very low resistance. Something less that ten ohms would be expected. If the belt is too loose, the same connections for the meter will so no continuity, infinite resistance. Remember that this is with the wire unplgged from the car harness, and you are reading between the wire to the switch and a ground point somewhere on the engine.

Big Dave

The tensioner appears to have normal electrics. After removing the short and completing the new belt job, I began having consistent belt tension warnings after 3 minutes of operating the car, although belt tension is still correct.

I put the short back on and plan on examining the tensioner closely when my re-tension is due, which should be in the next couple weeks. I didn't see a problem shorting out the tensioner again since it wasn't capable of giving me an accurate warning anyway. I'm guessing there might be some corrosion inside the tensioner, but I'm open to any thoughts or suggestions.

MichaelR

So, Dave, the splice was obvious? At or near where the wire plugs into the cover? Mine has no apparent extra wires, so I'll have to look for a short (intentional or otherwise) further upstream.

Oh, and I checked, the warning light does work when starting the car, so it's not a bulb issue.

BrianG

Since the switch "opens" to signal a loose belt, contact corrosion could be a "false-on" issue. When I rebuild my tensioner, I noticed that there was quite a bit of compacted "dirt" in the concavity of the "switch". I scraped out the majority of what resembled combustion chamber carbon, and then used the wire buffer-cup on the Dremmel-tool to brighten up the contact surface.

Of course I wasn't smart enough to check the switch for function before reassembly, and it's a bit late now because my bulb is dead. <img border="0" alt="[ouch]" title="" src="graemlins/c.gif" />

Big Dave

The splice was obvious to someone who had done a timing belt job before. I had not, so I never thought anything of the wire. Ell, another Rennlister who helped with the job, noticed the wire right away. We tested and confirmed that the electrics were operative with his ohm meter.