need help with vats module

[EagleMark]

I'm wondering if he's not programming a new chip.

I have talked to a few people over the years that didn't understand that a new chip had to be programmed for the changes in Tuner Pro to actually take effect. Easy new to tuning mistake.

Also the resistor bypass that is used for the VATS module is technically a parallel and series connection, electrically speaking. Since it is the only component connected to that pair of nodes, it is in series with the path of current, but parallel with the rest of the circuit.

I was thinking the same thing, wouldn't be the first to make changes and think it's done without burning a chip or re-flash.

Your the electronics dude, but when I did the VATS bypass with resistors it did not work in parrellel (side by side), when I took it out and read them it was only one... not both.. so which was it the bigger or smaller? I did not have correct amount so I had to use 2.

When I soldered them in series (in a row) it added up right on ohm meter and worked in car.

[Six_Shooter]

I was thinking the same thing, wouldn't be the first to make changes and think it's done without burning a chip or re-flash.

Your the electronics dude, but when I did the VATS bypass with resistors it did not work in parrellel (side by side), when I took it out and read them it was only one... not both.. so which was it the bigger or smaller? I did not have correct amount so I had to use 2.

When I soldered them in series (in a row) it added up right on ohm meter and worked in car.

What?

Are you talking about multiple resistors or the configuration in relation to the VATS module?

When doing the resistor replacement, the key cylinder gets disconnected from the circuit. If it doesn't than assuming the resistor value (placed in parallel with the circuit) is the same as the key the value will be half, which would cause the VATS module to not enable the fuel or the starter (if the starter disable is equipped).

If the resistor is placed in series than the values add and if both values were the same would double. Neither case would allow the VATS module to enable fuel and starter, because the value would be so far different than proper value.

If you're talking solely about the resistors, well connecting them in series or parallel would depend entirely on what the actual value of the resistors are and what value you actually need.

So to blanket say that they need to be in series would not be a correct statement.

[EagleMark]

I'm talking about bypassing the key switch that was bad by putting resistors in it's place, under dash. Eliminate key, VATS system still operational... except key part.


I had 2 different size resistors to add up to value of key pellet. Side by side they only ohmed to one of the resistors. In a row they ohmed to added value of both resistors and worked.

[Six_Shooter]

This was your original statement:

Measure the Resistance in key pellet in ohms, buy a resistor or resistors to match key. Put them in series, not parrallel in wires before key switch. This eliminates the key switch and always provides correct resistance to VATS module.

Which is confusing. It sounded like you were trying to suggest a particular way to add the resistor to the wire to bypass the key switch. As I said in a previous reply, electrically speaking the resistor, a single resistor as it sounded like you were talking about, is both in series and parallel with the target device electrically speaking.

I'm talking about bypassing the key switch that was bad by putting resistors in it's place, under dash. Eliminate key, VATS system still operational... except key part.


I had 2 different size resistors to add up to value of key pellet. Side by side they only ohmed to one of the resistors. In a row they ohmed to added value of both resistors and worked.

Again, this would depend on the actual value of the resistors. If one resistor is much large than the other, you will get a resistance value of slightly less than teh smaller value when connected in parallel.

Use this formula to see:

R1 x R2
-------
R1 + R2

The above formula only works with two resistors.

If you have multiple resistors in parallel, there are two formulas:
(Ignore the periods, that's just for formatting when posting, because of left justification.)

1
------
1.....1.....1
-- + -- + --
R1...R2...R3

That is 1 divided by the sum of 1 divided by R1 plus 1 divided by R2 plus 1 divided by R3.

Or to put it differently:

((R1^-1)+(R2^-1)+(R3^-1))^-1

That would be "R1 to the power of negative 1 plus R2 to the power of negative 1 plus R3 to the power of negative 1, and then the sum to the power of negative 1"

In series they simply add together, so I'm sure you know the formula for that. lol ;)

If you go through the formulas with different values especially when R2 is MUCH large than R1 you will see that the RT (Total resistance) is very close to that of the smaller value resistor.

I.E. A 1K ohm resistor in parallel with a 100K ohm resistor you will get a result of 990 ohms of total resistance. (990.0990099 to be more exact), so very close to that of the smaller value. I suspect this is why you saw what you did on your meter, without knowing the actual values you used.

[EagleMark]

Which is confusing. It sounded like you were trying to suggest a particular way to add the resistor to the wire to bypass the key switch. As I said in a previous reply, electrically speaking the resistor, a single resistor as it sounded like you were talking about, is both in series and parallel with the target device electrically speaking.

I see were I went wrong. It was 2 resistors and no where near same size. In series they added up right in ohms, in parralel they did not.

This was awhile ago so I don't remember actual values. But I did remember something else that may be useful or you could explain? I had them parralel after they did not work in car and used ohm meter and saw they were wrong? Ohms showed the big one IIRC? So I got another 2 and put them in series and ohms were perfect. I soldered them and rechecked and ohms were off... till it cooled and they were back to correct.

[Six_Shooter]

Yes, heat in a conductor causes resistance or in this case increased resistance.

When you measured the resistors after they failed, did you do so while still connected to the car, or were they isolated?

[EagleMark]

Isolated, on bench.

Your making me think I learned something wrong and just got lucky?

[Six_Shooter]

Isolated, on bench.

Your making me think I learned something wrong and just got lucky?

In that case all I can think of is that the smaller value resistor actually broke, but I was not privy to see it when you had the problem, so it's just speculation at this point.

I'm not sure what you would have learned wrong, care to elaborate on what you mean by that?

[ony]

if you had one of them adjustable resistor pods it might work.

[EagleMark]

In that case all I can think of is that the smaller value resistor actually broke, but I was not privy to see it when you had the problem, so it's just speculation at this point.

I'm not sure what you would have learned wrong, care to elaborate on what you mean by that?

Still works and does not work as I remembered?

Does not work.


Works.

[Six_Shooter]

Yep, top picture is 80 ohms, bottom picture is 555 ohms, quite the difference in resistance.

Calculation based on what is written on the resistor paper is 80.7 ohms (80.6954955, not rounded). Which supports what I was saying previously with the formulas.

By works and not works, I assume you mean that the VATS is bypassed or not bypassed.

That makes sense in a couple ways, 81 ohms is not a valid VATS value, and it's 474 ohms less than the 555 that is close to a valid value, 523 ohms is the actual value.

[EagleMark]

Those were just 2 resistors for example and I did not look up any VATS values.

What's even stranger to me is 1 resistor is .098 and 1 is .457 in series they show exact ohms of .555. In parralel it's not even the low resistor of .098, it's .081 ?

At least you can see what I was trying to explain about using resistors in series or parrallel for bypassing the key switch.

[Six_Shooter]

Those were just 2 resistors for example and I did not look up any VATS values.

What's even stranger to me is 1 resistor is .098 and 1 is .457 in series they show exact ohms of .555. In parralel it's not even the low resistor of .098, it's .081 ?

At least you can see what I was trying to explain about using resistors in series or parrallel for bypassing the key switch.

No, I don't see what you were saying.

What I'm trying to explain is that the need to place them in series or parallel is entirely to do with the actual value of resistors and the desired resistance value.

I struggled for a long time to understand why the resistance of parallel resistances of very different values was not just that of the lower resistance. What you have to realize is that both resistors are paths for current, and even though one resistor might be much higher resistance, it is still a path for current, and therefore will reduce the overall path of resistance. The formulas for parallel resistance verify this.

[EagleMark]

Thank God I have you to ask when I need to figure something out...

This stuff gives me a headache.

In this case with 2 different resistors and values if placed in series they came out to exactly what was marked on them and exactly what I needed to match ohms of key pellet.

[pmkls1]

You guys are making me have flashbacks of my electrical theory and principals course and how grueling it was because I had the instructor that everybody dreaded. He was the "all work no play" type so the faster you finished assignments he piled on more and harder ones in order to keep you working every minute you were in class. On top of that I had to carry our "farm boy" diesel specialist that hated messing with "waaarin' problems". I did learn about the series vs. parallel stuff, but I forget most of that now.

Anyway, as for the OP, it sounds like the vats module needs to be completely bypassed. Even if he is burning a chip and jumping the starter the fuel pump relay may not be getting power due to the vats module interrupting it. Since he can't get parts there that sounds like the best solution. Of course, that would require obtaining a schematic of the vats module so I'll try to dig one up. But, after we are sure that he is actually burning a chip we can see if jumping the fuel pump relay along with the starter fixes the problem.