Can anyone describe the belt tension warning light logic? I am getting a "!" button light some 3-4 minutes after startup. There is no attendent idiot light, however, I have a few burnt-out idiot lights including the pod "!" light. I'd like to neuter the belt-tension light temporarily to see if the "!" button light ceases to light. I don't know whether to "ground" the sensor wire or "open" it.

Incidentally, the "!" button light extinguishes on pressing the button, never to come on again, until the next startup (3-4 minutes later) even if driven for 2-3 hours.

I have just completed the timing belt replacement and rechecked the belt tension at 500 km. It's still "in the window".

Other ideas?

 

Have it looked at!
Could be little loose.
Good luck

 

Ground is all that is required to keep the light off ....some clever "technicians" tired of complaints about warning lights simply attach the wire to any one of the bolts on the engine . The customer never ever sees another t-belt warning ....ever ! The warning system is very basic if the tensioner arm is gounding to the pin on the tensioner it is happy . If it jumps away it triggers the warning but only after an aproximate three minute delay after starting . It is not good to ignore a warning BUT do not rely on the "system" to save you . It is also very easy to get false warnings .....

 

Hi Brian,

Danger, Danger, Danger,...

Great information from Jim about the delay. A wire goes from the tensioner to the front middle timing belt cover. Another wire goes from that cover to... The wires could be disconnected. You may be able to see the tensioner male blade by pulling the top right belt cover. I dunno'... You have to pull that one anyhow to re-check the tension. It is easy to find the other connection point on the front middle cover.

If you don't find the bad connection, park the car now. Take the hour or 2 to re-check the tension.
<img border="0" alt="[burnout]" title="" src="graemlins/burnout.gif" />

 

As I said above, I had checked the tension first because that was the most critical warning that I could think of. The aftermarket tool that Jim supplied shows the belt tension in the center of the window (perfect), so that's why I want to kill the warning system; to see if the "!" warning light discontinues.

Given the possibility of false indications, Jim, what's the fix? I thought the "sensor" was a bit of a flakey design when I was cleaning up the tensioner, during the rebuild. That nipple-into-the-hole thing has to be aligned pretty perfectly to avoid false/early contact.

Would low tensioner oil volume result in this indication?

I still don't understand why it only happens on initial start-up. Making the system a one-time indication doesn't make much sense.

 

The tension warning is set when the Central Warning Computer LOSES contact with ground thru the tensioner arm.

The tensioner bolt, which is grounded to the block, pushes on the arm, which is insulated from the block by the plastic bushings, thru several intermediate pieces. One of these pieces is a stout little coil spring surrounding an insulating sleeve.

As long as there is sufficient tension on the belt to keep this spring compressed, the arm is grounded tot he tensioner. When the tension falls, the spring pushes the arm away, breaking the electrical contact with ground.

There is a connector on the arm that eventually hooks to the Central Warning Computer thru the wire on the front of the belt cover. If Electrical contact is lost anywhere on this wire, the belt warning is set. There is a three minute delay when the engine is first started. This delay does not apply while the engine is running.

The oil in the tensioner serves multiple functions: lubrication, dampening, and heat transfer from the block to the Belville washers.

The belt tends to flutter due to rapidly varying valve spring loads. The oil helps to damp this flutter. If the oil level is low, the flutter can be high enough to break the ground contact, setting the belt tension warning.

The bimetallic Belville washers ease the tension slightly as the block and heads expand, to keep from over-stressing the belt. The oil helps transfer heat from the block to the bimetallic washers, which flatten as they get hot.

The oil is not connected to the engine oil supply, and does not hydraulic adjust the belt tension, as happens on some other engines.

In your case, the problem sounds like a bad connection on the sensor wire. Check the 1/4" flat spade connector just inside the lower belt cover, and the round connector on the outside of the cover.

You can temporarily ground the wire where it would plug into the round connector. Be VERY careful to keep the wire out of the accessory belts. If the waring is no longer set with the wire grounded, the problem is in one of the two connectors mentioned earlier. If the warning is still set, the problem is probably in the wire from there to the Warning Computer under the driver's footrest.

 

Hi Brian,
In the UK we usually find that the 32v engines need the belt to be set with the J Kempf tool to be at the "tighter" end of the window, or they can set off the light.

16v we usually set bang in the middle.

 

Brian,

I also had to set mine to the tighter side of the window, or I would get regular warnings right after startup like you do. But the belt tension light on mine does light up.

HTH

 

Thanks guys, I'll try Wally's grounding diagnostic first, then perhaps I'll tighten the belt a bit.

Two little items, Wally. If you would.

First: I don't recall an insulator inside that stout little spring. Absent that insulation, I would assume a possibility of a permanent grounded condition and hence a failure to set the light, rather than my condition. Correct?

Second: If it were a "bit of a loose belt" like Shane and John suggest, does the "only on start-up" scenario make sense?

 

The insulator is a plastic jacket around the metal rod that goes inside the spring. If the insulation isn't there, you have no tension warning system, as it would always be grounded.

Possible, but I would expect a warning at high RPM as well.

My '90 GT is set in the center of the window, and I have not had a warning in the 3500 miles since belt installation.

 

Thanks, all...... I'll post the results of the "grounded sensor" test.