stairmasterman911

So yesterday my '96 993 started refusing to lock. I changed the battery in the key fob hoping that would do it but no help there. When I push the button on the fob the light on the fob lights up, as does the light on the door, but no familiar click noise from the lock mechanism. Then after a few tries the car will unbelievably start. I've taken now to leaving the key in the ignition just to avoid the drama, but I know this is only good for secure spots like in my garage.
So what is it's problem? Tell me it's not a full restoration project!

KeninBlaine

Does the botton in the center console work to lock and unlock the doors? If not, the ACU may be causing the problem.

TMc993

Sometimes, this can be a symptom of a failing battery (Car, not fob) or a bad ground connection. I'd check the battery and ensure that it is in good shape, then clean the positive and ground connections on the car battery. Be sure to clean both the battery and chassis ends of the ground cable. Also, open the fob and carefully bend the spring connector up so the fob battery has good contact.

nine9six

What Terry said ^^^

When you put your key in the ignition and turn to position II, does the drive block light in the clock illuminate as it should?

stairmasterman911

Lo and behold, the button in the center console does not lock and unlock the doors! What's an ACU? I'm guessing not Abilene Christian Univ… The battery for the car is new ( about two or three months ).

KeninBlaine

Alarm Control Unit, located under the passenger seat. My power locks weren't working at all. Found a used ACU for about $250 and problem solved. Suggest first checking fuse on outside of ACU box and check that there is power to the fuse.

Spokes

^^^ ACU, look for 2nd hand one on Ebay.

nine9six

OK, the batter is new...Have the grounds been cleaned as noted earlier?

I would not spend a penny on an ACU, until all the usual (and cheaper) suspects have been eliminated. ACU's are fairly robust units and do not often go bad.

stairmasterman911

I'll for sure clean them this evening. Do you just undo them and scrape them with something like sandpaper then re-attach? Also the light in the clock that looks like a little key fob does light up. If it does come to an ACU is a used one OK? Major price difference -- $530 vs. $150 Used seems too good to be true so...

KeninBlaine

I agree with nine9six regarding checking other possibilities before getting another ACU. Regarding new vs used ACU, I took a chance on a used one and lucked out, and saved $300. Plus, it was available within 15 miles from me, so was able to pick it up quickly. If you're concerned, then spend the extra and get a new one. My symptoms were exactly the same as someone on an older post, so I was pretty convinced it was my ACU.

TMc993

Sandpaper or a wire brush will do. You can buy a little device at any parts store that is designed to clean clamps and posts. Sand the insides of the battery clamps, the posts, the chassis end of the ground cable and the chassis mounting point until all are shiny. Use some dielectric grease on the surfaces as you put it all back together. Be sure you have your radio code so you can reprogram your radio.

Spokes

I did the all the pre-checks: earths, switches, battery, thumped the ACU with a hammer! Fault was intermittent which doesn't help as well. Anyways, I bit the bullet on a 2nd hand ACU and it fixed the problem.

nine9six

Yes Spokes, but as you noted, the checks need to be completed first...^^^

stairmasterman911,
Can you lock your car with your fob? If yes, are the door top LED's blinking in rapid succession at first, and then settle to a single blink every 3 sec or so?

stairmasterman911

No - can't lock it with the remote. The lights do blink though. Also won't lock with the button on center console.