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Posted by: The Cabinetmaker Aug 4 2012, 08:44 AM

Picked up a vdo gauge with matched sender. The sender has two terminals. the gauge has one marked g, and two marked +. Do i just hook them up either way?

Posted by: The Cabinetmaker Aug 4 2012, 10:30 AM

Ok, I think I figured it out. I could not read the marks on the gauge (poor old tired eyes) till I took a macro pic. The three marks are a G, a+, and a ground symbol. So, + is power, ground is obvious, Is the G for the gauge from the sender? the sender has two terminals. Is this a dual sender? one terminal to the gauge, and one for the idiot lite on the dash?

Posted by: jcd914 Aug 4 2012, 10:34 AM

[quote name='The Cabinetmaker' date='Aug 4 2012, 09:30 AM' post='1719127']
Is this a dual sender? one terminal to the gauge, and one for the idiot lite on the dash?

Yes.

Posted by: The Cabinetmaker Aug 4 2012, 11:47 AM

I hooked them up as I described, but the gauge pegs to the high side. + to hot, and the ground symbol to ground. Even with the gauge disconnected from the sender WTF?

Posted by: Porschef Aug 4 2012, 12:01 PM

Curt,

That should be correct. G is gauge, I have the same setup. I did a test prior to mounting the gauge, connected directly to the battery, and the lead to the sender. Ensure that your ground is good.

Let me know if you need a pic.

Posted by: The Cabinetmaker Aug 4 2012, 12:17 PM

I have hot and ground connected to the battery. Gauge is pegged when power is applied.

Posted by: The Cabinetmaker Aug 4 2012, 12:46 PM

I did a google search and found a thread on the samba. Poster had the same problem. It was suggested that he disconnect the gauge wire from the sender and ground it. If the gauge drops to zero, then the sender is bad. I grounded the gauge wire from the gauge to sender and sure enough, it zeroed. I used no teflon tape or sealer of anykind so I know it has a good ground. Guess I'll have to call vdo to make sure I have the proper sender and try to get another.

Posted by: type47 Aug 4 2012, 12:57 PM

Isn't this an oil PRESSURE gauge? Dual sender to idiot light would be a pressure, not temp gauge. Oil temp sender is in the taco plate under the engine.... You don't show the face of the gauge but if it's a temp gauge it would be improperly matched to a pressure sensor.....

Posted by: The Cabinetmaker Aug 4 2012, 01:11 PM

Uh, duh. Your the only one to catch that, including me. Thanks. Title changed.

Posted by: jcd914 Aug 5 2012, 01:29 AM

How do you have the sender mounted so that it has a ground?
Mine would not fit into the threaded hole for the oil pressure switch, due to the sheetmetal and distributor.
You might try a jumper from the sender to ground to be sure you have a clean ground.
Have you tried both terminals on the sender?

Jim

Posted by: The Cabinetmaker Aug 5 2012, 03:53 AM

Yes and yes. Neither terminal works. No juice to idiot light either

Posted by: edwin Aug 5 2012, 07:31 AM

Many dual post senders are just for oil pressure without the idiot light.
May want to check with a multi meter what the resistance is between the posts.
I expect one will need to go to ground and the other to the gauge.

Posted by: Java2570 Aug 5 2012, 08:01 AM

I just looked at how my sender is hooked up and the G connector goes up to the oil pressure gauge, and the one marked WK hooks into the wiring harness in the engine bay. There is a bracket holding the sender to the engine and that bracket is grounded to the engine case. VDO seems to indicate that the sender gets it's ground from the engine case.... My sender isn't hooked to my oil pressure light though so I'm not sure how that works.

Posted by: Java2570 Aug 5 2012, 08:06 AM

Do you have these instructions? See the lower right corner for schematic on the dual sender hookup....


Attached image(s)

Posted by: The Cabinetmaker Aug 5 2012, 08:17 AM

My sender has no markings of g or wk. Its hooked up as shown in your illustration, except it goes straight to battery now. It will be wired permanently to the key when i install it in the console

Posted by: Java2570 Aug 5 2012, 08:39 AM

Actually, I'll take back that about my idiot light, it is hooked up and working. I'm not the one who wired it (PO) but it all seems to work ok. That's strange that your terminals on the sender aren't marked; makes it much harder to know what you are hooking up!

Posted by: The Cabinetmaker Aug 5 2012, 08:49 AM

That's what makes me think the sender may be wrong

Posted by: Dave_Darling Aug 5 2012, 06:07 PM

What is it that goes straight to the battery?

The sender for the light only provides a ground. The power goes to the light, then to the sender. If the pressure is low enough the sender connects its terminal to the case, grounding it and completing the circuit. That's when the light goes on. The terminal for the light should be labeled "WK".

The sender for the gauge provides some resistance to ground. The power comes from the gauge, then goes through the variable resistor, and is grounded through the case of the sender. This terminal should be labeled "G".

So you would not be looking for voltage anywhere on the sender, just ground or resistance.

--DD

Posted by: Black22 Aug 5 2012, 07:33 PM

I had a gauge wire that shorted for a split second and it blew a fuse (on Toms fuse block) and fried the sender. When my sender was broken the gauge pegged out on the high side like you mentioned. My idiot light was still functioning though.

I say the sender is bad.

I replaced the sender and all is good.

Posted by: michael7810 Aug 5 2012, 07:44 PM

NOt sure if you tried this but the sender should also be grounded as if it were installed on the engine. If you are just testing it on the bench this might be your problem.

Posted by: Drex Jun 15 2023, 10:32 AM

here is a picture of where the oil pressure sensor attaches to engine
this was off my parts car
it has a single lead into the engine wiring harness

my project 914 has a oil line screwed into this hole
which is attached to a two pole sensor
one lead to engine harness and the other goes forward thru firewall
(picture to follow)

i can see it would be tough to take in and out

D Rex

Posted by: Drex Jun 15 2023, 10:49 AM

Posted by: Geezer914 Jun 15 2023, 11:35 AM

Use a braided brake line from the oil pressure port to the sender. You don't want a rubber line bursting covering the engine with oil and possibly blowing the engine!

Posted by: Drex Jun 15 2023, 02:00 PM

sounds like a very good idea

could the same thing be said about the fuel lines as well
as the pressure is also pretty high?

D Rex