Re: Electrical Gurus
[Re: 71birdJ68]
#3072666
08/30/22 04:09 PM
08/30/22 04:09 PM
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Joined: Jan 2003
Posts: 18,389 UPPER MICHIGAN, MARQUETTE COUN...
NITROUSN
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 18,389
UPPER MICHIGAN, MARQUETTE COUN...
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As I remember it was with the Rallye gauge cluster. It was part number 2983848. The senders were 249522 up to march 1971 and 3488609 after March 1971. Senders were the same on all car lines. So was the Rallye cluster only available on those engines? That's the only difference I see.
Last edited by NITROUSN; 08/30/22 04:10 PM.
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Re: Electrical Gurus
[Re: 71birdJ68]
#3072669
08/30/22 04:13 PM
08/30/22 04:13 PM
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Joined: Jan 2003
Posts: 74,905 U.S.S.A.
JohnRR
I Win
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I Win
Joined: Jan 2003
Posts: 74,905
U.S.S.A.
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Are there any electrical guys that understand why they did things the way they did it back in the day? What I'm talking about is on the 71 B&E body cars with an oil pressure gauge. There was what was called a resistance wire (service manual) that hooked to the sending unit and then went to the harness. With a ohm meter set to the 20 scale it shows a little over 30 ohms, The service manual shows this wire for both the Hemi and 440 cars and my 383 RR had this wire. Everybody that I have asked has never seen one, or doesn't know what it is for. I'm wanting to know what it did in reference to the operation of the gauge and is it required? What year is your road runner ?
running up my post count some more .
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Re: Electrical Gurus
[Re: 71birdJ68]
#3072727
08/30/22 05:53 PM
08/30/22 05:53 PM
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Joined: Jan 2003
Posts: 18,389 UPPER MICHIGAN, MARQUETTE COUN...
NITROUSN
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 18,389
UPPER MICHIGAN, MARQUETTE COUN...
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On the rallye cluster, you could get it even on a 318 2 door. Satellite Sebring could be had with a rallye cluster and a 318. Well if thats the case than the only reason I see is pressure. Its possible the motors in question had a very high pressure pump and using the resistor wire allows the gauge to read in the normal range. With out the wire I would assume the guage might be pegged at higher rpm's. That's the only logic that makes sense.
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Re: Electrical Gurus
[Re: NITROUSN]
#3072739
08/30/22 06:40 PM
08/30/22 06:40 PM
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Joined: Mar 2011
Posts: 3,055 Michigan
A727Tflite
master
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master
Joined: Mar 2011
Posts: 3,055
Michigan
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On the rallye cluster, you could get it even on a 318 2 door. Satellite Sebring could be had with a rallye cluster and a 318. Well if thats the case than the only reason I see is pressure. Its possible the motors in question had a very high pressure pump and using the resistor wire allows the gauge to read in the normal range. With out the wire I would assume the guage might be pegged at higher rpm's. That's the only logic that makes sense. I think you are correct. My 71 Hemi GTX had this wire in the original harness. Somewhere along the harness and this wore got cooed. When I went though the vehicle to clean it up I ordered a new harness and this “resistance” wire was not included. Stock motor with an accurate aftermarket gauge shows around 75-80 lbs. of pressure. The Rallye gauge is almost pegged at this pressure.
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Re: Electrical Gurus
[Re: A727Tflite]
#3072752
08/30/22 08:24 PM
08/30/22 08:24 PM
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Joined: Aug 2003
Posts: 43,007 Bend,OR USA
Cab_Burge
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I Win
Joined: Aug 2003
Posts: 43,007
Bend,OR USA
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Mopar used two different oil pressure senders, one for the oil light and the other one which is much bigger in outside diameter is for oil pressure They are distinctly different in appearances: scope:
Last edited by Cab_Burge; 08/31/22 01:32 AM.
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Electrical Gurus
[Re: NITROUSN]
#3072837
08/31/22 09:08 AM
08/31/22 09:08 AM
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Joined: Feb 2010
Posts: 1,645 Phila. Pa.
Mattax
top fuel
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top fuel
Joined: Feb 2010
Posts: 1,645
Phila. Pa.
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As I remember it was with the Rallye gauge cluster. It was part number 2983848. The senders were 249522 up to march 1971 and 3488609 after March 1971. Senders were the same on all car lines. So was the Rallye cluster only available on those engines? That's the only difference I see. I think your answer about calibration issues is generally correct. The details we would have to figure out, but essentially there seems to be a change in calibration. The aftermarket replacements, including the one I bought from BRE, read too high with the original '67 gage in my car. Scroll through here for that. https://www.forabodiesonly.com/mopar/threads/oil-pressure-gage-and-sending-unit-revisited.490485/ Note Redfish worked at Chrysler dealer for years - so I'm sure he's correct that some gages were tweaked to deal with a specific production issue but I think he's saying that was 67 only. (The gage in my '67 worked correctly for years until the sender started spraying oil) OP can do what I did to check the gage. Get some resistors, I just happend to have some 11 ohm in the box, and or a reostat/pot. Then hook them up to the sending wire as a simulation of the factory spec'd sender sender resistance. For the 67 A body oil pressure gages. 80 psi is the top mark, and 40 the middle. The sender should have 10-12 ohms at 80 psi. around 23 at 40 psi, and around 74 ohms at zero. My tests showed 46 ohms would bring the Barracuda's gage to the first mark (10 psi) and plotting that it looks to be correct but I can't guarentee that's the spec. My temporary solution was to splice in a short length of resistance wire. It may result in a less precise response, but critically (for me) keeps maximum amperage through the gage in the range it is was intended. I now have an NOS sending unit. If it tests correctly it will eventually go on the car,
Last edited by Mattax; 08/31/22 09:22 AM.
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Re: Electrical Gurus
[Re: Mattax]
#3072922
08/31/22 02:12 PM
08/31/22 02:12 PM
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Joined: Aug 2003
Posts: 43,007 Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,007
Bend,OR USA
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The senders, water temp, oil pressure and fuel level read ohms not voltage, amperage or Watts, no current going through them, I THINK
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Electrical Gurus
[Re: Cab_Burge]
#3072926
08/31/22 02:22 PM
08/31/22 02:22 PM
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Joined: Jan 2003
Posts: 5,435 So Cal
Sinitro
master
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master
Joined: Jan 2003
Posts: 5,435
So Cal
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The senders, water temp, oil pressure and fuel level read ohms not voltage, amperage or Watts, no current going through them, I THINK Basically the senders have a built-in variable resistor circuit that reads between the 5V and ground.. Since the gas, water temp, oil pressure gauges are essentially a 5V DC meter by adjusting the resistance(ohms) to ground changes the voltage read by the meter.. Just my $0.02...
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Re: Electrical Gurus
[Re: Cab_Burge]
#3073072
08/31/22 09:26 PM
08/31/22 09:26 PM
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Joined: May 2019
Posts: 6,174 nowhere
Sniper
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Joined: May 2019
Posts: 6,174
nowhere
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the gauges have -5 volts to them to make them read the ohms, not to the senders You really don't know how electrical circuits work The gauges and senders are both have voltage on them. As the resistance of the sender changes, the voltage dropped across it varies, changing the voltage left for the gauge to drop, that's what moves the needle on the gauge,
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Re: Electrical Gurus
[Re: Cab_Burge]
#3073114
08/31/22 11:44 PM
08/31/22 11:44 PM
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Joined: Jan 2003
Posts: 5,435 So Cal
Sinitro
master
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master
Joined: Jan 2003
Posts: 5,435
So Cal
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the gauges have -5 volts to them to make them read the ohms, not to the senders CAB... See the attached schematic as it better explains how a basic fuel gauge circuit works. For the Mopar systems, the 5V is supplied by the voltage limiter device is found on the gauge cluster PCB or sometimes built into the fuel gauge of most Mopars in the 60s/70s/80s. Just my $0.02...
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