[T2] Gas gage weirdness

[c.dreike]

Yeah, there are no labels or terminals on the bay gauge. It grounds 
through the mounting screw. Who would have thought.
Back to the turn signal switch. I'm on the third switch. This one works 
mechanically, but electrically the rear flashers run until I carefully 
jiggle the switch arm. Will keep you folks posted.

Chris


On 2/22/2019 1:13 PM, Bob Reuter wrote:
>
> if I have electrical problems I almost always check the ground first, 
> VW was very good at hiding grounding locations
>
> Bob
>
>
>
> On Fri, 22 Feb 2019, c.dreike wrote:
>
>> I figured it out!!!  Simple as grounding the gauge case.
>> I pulled the gauge in my 64 from the dash and suddenly it didn't work 
>> either! I noted that there is a ground terminal on the back and that 
>> the mounting bracket would also provide ground. Once I added the 
>> ground wire it worked properly. Amazing.
>> I went back to my bay gauge and added the ground to the case and the 
>> gauge now works correctly. Amazing!
>>
>> Thanks for the input.
>> Chris
>> 71 Sunroof
>> 64DD Kamper Kit
>>
>> On 2/21/2019 4:47 PM, c.dreike wrote:
>>> Started testing my gas gage and sender. The sender worked when I 
>>> installed it. Currently the tank is very low and the sender reads 
>>> about 80 ohms. According to The Samba this is about correct. The 
>>> senders run from about 3-5 ohms at full to about 70-80 ohms at empty.
>>>
>>> When connected, both of the gauges I have read full and a little 
>>> past. The battery voltage is about 11.98. The voltage across the 
>>> gauges are 6.57 on the original gauge and 7.98 on the reproduction 
>>> gauge.
>>>
>>> On the test bench connected to a bench supply, the original gauge 
>>> reads full at about 6.5V and the reproduction gauge reads full at 
>>> about 7.2V. As I reduce the voltage to the gauge, the reading goes 
>>> down. At 0 volts the gauges read empty.
>>>
>>> Per the test specs in Bentley, the gauges should read full at about 
>>> 12V, battery voltage. Both my gauges peg when attached to full 
>>> battery voltage.
>>>
>>> I have double checked the wiring against the schematics and all 
>>> looks correct. The circuit looks simple enough. +12V on one side of 
>>> the gauge. The other side of the gauge connects to the sender (5-80 
>>> ohms) and the other side of the sender connects to ground.
>>>
>>> I'm an electrical engineer with lots of experience with simple stuff 
>>> like this and this stuff makes no sense to me. I must be missing 
>>> something. (Kinda like mistaking the wire stripe colors on the turn 
>>> signal)
>>> Anyone have ideas on what I should be looking for or doing 
>>> differently? I'm stumped. I'm about to build an inverting 
>>> operational amplifier circuit that would drive the gauge so that it 
>>> would see 0 volts at empty and about 7V at full.
>>>
>>> TIA
>>> Chris
>>> 71 Sunroof
>>> 64DD Kamper Kit
>>> _______________________________________________
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>>> type2 at type2.com
>>> https://www.type2.com/lists/type2/listinfo
>>
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