Normal Voltage Drop?

[Sharp64]

I did look through various threads but didn't find this particular info. What is the normal voltage drop when headlights are turned on? In testing my voltage with the car running and no lights on, there is 6.2-6.4 to 30 on the light switch. Coming back out 58b to the fuse is good at 6.2. If I turn the lights on, with the car running, the voltage going into 30 drops to 5.8. Same coming back out on 58b. 58 however, drops down to 5.4 Is this normal? I'm pretty certain I have some cleaning to do, but trying to determine what is considered a normal drop when something goes through a switch or when the lights or other accessories are on?

[Danwvw]

For these readings to mean anything you need to factor out the battery drop in voltage when you turn on the lights. A good solid system is not going to loose more than 1/2 a volt though. Probably need to check your voltages relative to the neg battery post with the car not running too. Some of the voltage drop could be on the grounding side. Make some comparisons.
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1960 Beetle And 1679cc DP W-100 & Dual Zeniths!

[bluebus86]

[Sharp64]

Ok. I get having to test the drop at the battery. Makes sense. If the drop is equivalent to what I'm getting to the switch then I know I'm pretty clean between those points. I also what you're saying BB. I don need to clean the switch terminals and the connectors. I'll do that and see what my reading are after checking the V drop at the battery then check the other readings at the headlight.

[Eric&Barb]

You will need to solder up these to get rid of voltage drops in these:

http://www.thesamba.com/vw/forum/viewtopic.php?t=483901&highlight=headlight+switch+rebuild

And

http://www.type2.com/library/electris/vw-hauptlicht-schalter.html
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In Stereo, Where Available!

[Sharp64]

Fuse box is brand new so I'm actually not losing anything through the fusebox. I had planned on taking the light switch out when I pull the wiper motor out at some point.

[bluebus86]

[EVfun]

The quickest test is to get the car running at a fast idle and turn everything on. Start at the battery and work forward, measuring the voltage after each connection. No drop is ideal and unrealistic. Small drops are expected, the headlights tend to be the biggest ones. You should have only a fraction of a volt loss total between the output side of the headlight fuses and the battery voltage, certainly well over 6 volts with a running engine. This same test applies at the coil, and the brake lights and...

If you have a "map" of the actual voltage at different points I'm sure someone will point out the bad ones. Basically, the less the load the less the acceptable voltage drop. I'd do this all at once for one baseline of voltage losses.
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[Eric&Barb]

[Sharp64]

Ok. I'll put this somewhere on the to do list that is unfortunately getting longer and longer😂

[Eric&Barb]

Eventually the list will get shorter. Just try to get a few things done per week.
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[Sharp64]

[Sharp64]

Ok. So to diagnose if there is possibly a bad switch... I am getting 6.4 volts to fuse 8 and this is translating to 6.4 to 30 (measured on both sides), if I ground the VM on a common ground and clip the alligator clip to post 50 on the ignition without the load of the starter solenoid and turn the key, I am getting 6.0volts out of the switch. If I put the wire to the solenoid back on to post 50 and clip the VM to the fitting and turn the key, I get a momentary reading of about 5 volts... Does this indicate a bad switch or is the solenoid taking that much draw? If its drowing that much, does that indicate something is most likely bad at the solenoid which is drawing too much? I also did a point to point measurement between 30 and 50 when cranking and got a reading of 1.3. Not sure what this info is telling me?

*Edit - Would the way to indicate if this is a voltage drop vs draw to measure across the battery when cranking and comparing the amount of draw when cranking at the ignition?

**Edit- Measuring across the battery I am getting 6.4 volts. When I put the key in the ignition, and turn it to the first position, I see draw at the battery of .04. If I turn the key to the cranking position, I see the voltage drop to about 5.8-5.9. Is this telling me that there is something wrong with the ignition that it is drawing an additional .8-.9+ volts? Crappy switch?

***Edit - If I clip to a common ground and measure at 30. Initially a reading of 6.4v. Drops to 6.32 with key to first position and drops to 5 -5.4 when cranking. Hard to get a good read on it when cranking as its momentary and can actually drop to anywhere from 4.8-5, but pops up quickly. Which is the correct reading?

[EVfun]

When the engine is cranking over it is acceptable to have the voltage fall to as low as 5 volts. The starter is by far the largest load on the car and that load has to be carried only by the battery because the charging system is running yet. The voltage everywhere will drop because it drops at the battery.
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[Sharp64]

[bluebus86]

[Sharp64]

Makes sense. I figured it was easier giving connection numbers than me trying to figure out the exact terminology for the various ignition positions. In previous posts where people have been diagnosing issues I've seen it done in both the question and the reply so figured that was the best way to avoid confusion. I'll try to be more explicit in the future.

[flyboy161]

[bluebus86]

[Sharp64]

Thanks BB I'm using the diagram from 64. I assumed since I was discussing voltage drops in the ignition circuit it would be assumed I was discussing the ignition when referencing terminal post numbers. I was taking Flyboys lead when he was using the same references in another thread. I guess next time I can insert the term xx on the ignition or xx on the light switch to clarify if that's easier?

Either way, I'm getting s better understanding of the circuits and the reasons for some of the drops and draws.

Flyboy, when I did some retesting I clipped the black wire of the VM to 30 with the wire from fuse 8 attached and the red probe from the VM to 50 on the ignition switch with the wire to the solenoid off and took readings again and getting very little drop now. I think my readings before may have been from a poor connection of the alligator clip and the outside of the connector.