'86 Coupe with 117,000 miles. Ignition Lock "jammed", so I read the resistor pellet in the key, replaced the ingnition lock (oh, fun!) and installed a proper value resistor in the wires to the VATS unit.
Now the ignition lock turn on fine, but NO sign of engaging starter, and am hearing a "sizzle" sound under the dash when key is engaged to the start position....advice appreciated!!! :banghead:

 

Use a digital VOM, their ohmeters are accurate and measure the fixed resistor on your VATS plug and compare it to the key pellet. They both must be within 5% of the book value. Also, the 2 wires from the steering column must not be plugged into the socket that goes over to the VATS module or you will have the pellet in parallel with the fixed resistor and VATS will not close the start enable relay. With the ign in run, when you connect the fixed resistor you should hear the VATS relay click behind the center of the dash.
VATS may be activated with your fixed resistor, but 12v must still go through the clutch safety sw (gear selector sw if automatic) before it goes to the starter solenoid. Jump the clutch (gear selector sw) switch and try a crank. If no crank, jump 12v to the jumped clutch/gear switch. The starter must crank if the connection through the firewall connector and down to the start solenoid post on the starter is ok. You can test the VATS circuit by jumping the clutch/gear sw and measuring the volts on the jumper wire when the ign sw is in crank position. You will have 12v on the jumper when the ign is in crank because the fixed resistor will allow VATS to close the start enable relay and the ign sw will pass 12v through its crank contacts.
Here is the path for 12v to the start solenoid on the starter: batt through a fusible link , through the firewall connector to the ign sw, from the ign sw "crank" contacts to the start enable relay contacts to the clutch (gear selector) switch, through the firewall connector and then to the start solenoid terminal on the starter.

 

Ahh, you're right...I need to upgrade to the digital age! The old Multimeter is an antique...bought that when i was restoring my '68 Z28 in 1977! I should have kept the Z28...fixed everything with a hammer, screwdriver and a 1/2" socket! (my age is showing)

Anyway, super advice...I will check it out tomorrow...just what these old knees needed...more hours on the concrete with my head under the dash!!! Seriously, thanks again...I will let you know what I find out! :cheers:

 

Just fixed a VATS issue... take your old key and new one to dealer and have them check the key code (1-15), make sure new is same as old... my new key lost its value and i had to replace it... i also added the 3-position VATS module from MAD...just in case something like this happens again...

 

Well, JFB gets the Mechanic Of The Year Award from me!!! He was absolutely correct when he advised ditching my old Analog Multimeter and getting a digital one to measure the VATS resistor! I bought a new digital MM at Radio Shack, checked my old key, got 3010K, bought five 3000K resistors for $.99, popped one into the VATS harness, and hit the new (cheap) ignition switch, and VROOOOM!!! The old girl sounds better than ever! End of problem, plus, if I want to disable the car for theft prevention, I can just reach under the dash and pop out the resistor and she ain't going anywhere under her own power (of course, there are always tow trucks!). Thanks to all who helped on this one..just goes to show...you CAN teach an old dog new tricks! :hurray:

 

Sounds like you fixed your problem... but regarding theft issues, why not dump the fixed resistor and reconnect the VATS wiring to the ignition switch (i.e. back to factory)? My understanding is VATS issues often stem from worn ignition switches, and you've already replaced it... just keep the ignition key clean and make sure the pellet isn't worn down.

 

Strictly a matter of dollars vs. results...the "cheap" new ignition switch was $12.00. A new VATS ignition switch was $45.00, plus the royal PIA of threading the VATS wiring out of the steering column to reconnect it. At 117,000 miles, this old girl is never going to see a NCRS judge, so originality isn't a big deal...functionality was the goal. Otherwise, you are 100% correct...it could be redone back to "original" at any time. :seeya