jdubois77354

Well, I have done a search of the site and got some pretty good ideas that the theft deterrent module has failed. The symptoms yesterday morning were a completely discharged battery. Upon recharging the battery the alarm started flashing the lights and will not remain reset.

Oh, the car is a 1986 automatic that we got a couple of years ago, fairly low mileage (80k) and pretty much like new and always well cared for. My wife has been using it for a daily driver since.....great car. No issues until yesterday morning. A bit more information the theft deterrent module no longer sounds the horn, it is disconnected someplace, so I am guessing this is not the first time this car has done this.

So, I understand that the entire system can be disabled by unplugging the theft deterrent module ? I must be dumber than a box of rocks because I am not finding the module...I understand it has 13 wires and it can be found behind the breadbox panel, which I have removed.

I have the schematics and have verified the voltages where I can without laying hands on the module itself. It appears as if the module has failed in that it will not reset consistantly and even when it shows and acts as being reset it still will not allow the starter to power up.

So, how do I get to this module? Is removing it going to allow the car to function until such time as I locate a replacement?

Thanks in advance for any assistance and sorry for what is most likely dumb questions and an even sillier problem.

Jim

VQT88Vette

Look at a thread started by LESLIE SMITH, there is a picture of the VATS module. It a b*&^h to take that out

jdubois77354

Appreciate the quick response. I have printed out the manual details in the link, on the name you sent me. I suspect I need the full manual so as I can find the location of the parts as well as how to deal with some of the panels.....I have gone though the alarm power up and power down steps from the manual, all to no avail. I have only started to test the various parts per the test process.

I have discovered there is a second alarm system in this car, it is buried away under the drivers lower dash. It appears to be doing nothing, seems to have no power to any of its 3 relays, but the standard alarm blinks the parking and tail lights only as the horn is disconnected.

So, right now it still appears as if the TDM (theft deterrant module) has failed. But I have testing to do. So, I remain in a quandry at the moment.

jdubois77354

The plot thickens.....since the testing procedure outlined in the Leslie Smith document...referenced by VQT88Vette....did not work for me as outlined in the instructions..the alarm would not reset and the car blinks its parking lamps instead of honking the horn.

I decided to order a proper service manual, but of course it will take a week or so to get here.

So, I needed to check the connection on the Vats decoder resistor and do a substitution of a resistor as suggested in the Smith string....

As I mentioned previously there was another alarm......Much to my surprise I found the remnants of 3 after market alarm systems all tucked away under the hush panel on the drivers side. One was a simple disconnect for the distributor and the starter enable relay, one was a pretty conventional unit that is what I think was blinking the parking lamps. The 3rd alarm? Looks almost like a very old Lo-jack...most likely just an alarm. Talk about a rats nest of wiring.....looks like a effort between several hairless monkeys, a deranged rocket scientist, and at least a case of cheap beer. There were 5 relays in the one alarm system alone, all conntected by lots of 3M tape and quick connects. I am wondering how this car ever ran......amazing that it did.

Anyhow, there was no real choice but to gut it all. It was such a mess there was no way to troubleshoot it.

Right now, I have everything pretty well back together and the wiring cleaned up, other than the 5 wires that go to the fog light switch. These 5 wires had been run to the rats nest of wiring...I see no place they originally attached. It appears as if one of the alarms in the car used this switch to arm and disarm the alarm system.

The 5 wires are in a flat ribbon configuration...any suggestions where these might go? I would guess my service manual will tell me when it gets here, but who knows when that might be. If I could prevail on one of the forum to point me in the right direction it would be most helpful....

Thanks to all for your help and particularly VQT88Vette for assistance already rendered.....

Jim

C4driver99

Call GM and ask them. Or you could be like me and just start snipping wires eventually youll get the right one

Redeasysport

You said it yourself before you play with the wiring go to www.helminc.com and get the factory service manual for your car.It has everthing you will need to repair your car.

C4driver99

jdubois77354

Readeasysport, the manual is on order, I ordered it Friday airmail. I hope to have it this week, just trying to get a headstart. I suspect you are correct that I need the manual in hand to make real progress.

thanks,

Jim

C4driver99

Hope it all works out well for you. My vats is prolly about to screw up. Any info would be greatly appreaciated

jdubois77354

After I gutted out all the aftermarket alarm(s) and carefully soldered and shrink wrapped all the cut wires, we had ignition! The 5 wires that I thought went to the fog lamp switch were in fact going to a shock and vibe switch that was attached to the back of the dash by the switch. After I figured that out, removed it, and re-did the wiring as mentioned above, all is well. Car runs, everything works, and the standard GM security system is operational. So, outside all the bad wiring, the biggest problem was user error! Or pilot error if you prefer. In any event, the wife is now back underway. But she wants to trade me the Vette for my truck....she is concerned about reliability.

So, now I get the toy to enjoy, so all is well.....until she decides she needs something more sporty.....

VQT88Vette

I wish I have your ability on trouble shoot my alarm issue

jdubois77354

Guess my electronics education goes way back, ham radio many many years ago, commercial radio telephone license, ee, me, and 40 years playing with computers....and almost all of that was something other than engineering so I still like to solder some wires and troubleshoot some problems.....with all that BS said, I flat got lucky on my problem.....I took out everything that didn't belong, put back everything that had been disconnected to where it belonged, and it worked. Even a blind hog finds an ocassional acorn....