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Re: Electrical Gurus [Re: 71birdJ68] #3073584
09/02/22 02:34 PM
09/02/22 02:34 PM
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Mattax Offline
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Originally Posted by 71birdJ68
That is exactly what my wire looks like, even down to the friction tape. Now, my car is a 383 car, so I don't know why it has one. I think the reason I'm wondering about all of this is cause the after market sending units now a days are crap compared to originals, so I'm just going to see how the gauge reads and then decide weather to us the wire, or not.


OK. You lost me. My illustrations on FABO show a test with a resistance wire spliced into a reprop harness, and tests of sending units pressure vs resistance.
Any car with an oil pressure gage (included in the rally instrument cluster) would get the oil pressure sending unit. Which sending unit depended on the year and possibly model. If there was a special sending unit or gage calibration for particular hi-perf engine option, it is probably listed in the books or the TSB.

For those wondering how the gages work with the senders, Chrysler's Mr Tech can help out
http://www.web.imperialclub.info/Repair/Lit/Master/227/Page01.htm

Re: Electrical Gurus [Re: Mattax] #3073594
09/02/22 02:54 PM
09/02/22 02:54 PM
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Morristown Tn.
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Up Date: I found my original sending unit and on the hex part where you put a wrench to tighten it is stamped on one flat80 and on another flat is stamped OK and Introl on the housing, which is I guess who made it.

Re: Electrical Gurus [Re: Mattax] #3073602
09/02/22 03:12 PM
09/02/22 03:12 PM
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Originally Posted by Mattax
Originally Posted by 71birdJ68
That is exactly what my wire looks like, even down to the friction tape. Now, my car is a 383 car, so I don't know why it has one. I think the reason I'm wondering about all of this is cause the after market sending units now a days are crap compared to originals, so I'm just going to see how the gauge reads and then decide weather to us the wire, or not.


OK. You lost me. My illustrations on FABO show a test with a resistance wire spliced into a reprop harness, and tests of sending units pressure vs resistance.
Any car with an oil pressure gage (included in the rally instrument cluster) would get the oil pressure sending unit. Which sending unit depended on the year and possibly model. If there was a special sending unit or gage calibration for particular hi-perf engine option, it is probably listed in the books or the TSB.

For those wondering how the gages work with the senders, Chrysler's Mr Tech can help out
http://www.web.imperialclub.info/Repair/Lit/Master/227/Page01.htm



For some its making a mountain out of a mole hill.

Re: Electrical Gurus [Re: Sinitro] #3073614
09/02/22 03:55 PM
09/02/22 03:55 PM
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Originally Posted by Sinitro
Originally Posted by Cab_Burge
the gauges have -5 volts to them to make them read the ohms, not to the senders scope


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... wink
Looking closely at your diagram there are no wires, voltage supply, hook to the indicator needle, correct scope
That being so the coils read the ohms from the sender and pull the needle towards them when they have the highest or lowest ohms to make them work like a magnet, correct workwrench
As already posted any voltage sent into the gas tank sender could and would cause an explosion in the tank when the ignition key was turned on activating the sender when jumping across the parts to make the connection to read it, correct work shruggy
Ohms don't spark grin stirthepot boogie scope devil


Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: Electrical Gurus [Re: Cab_Burge] #3073680
09/02/22 09:09 PM
09/02/22 09:09 PM
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Lets get back on topic, why did some cars have these wires and others didn't.

Re: Electrical Gurus [Re: 71birdJ68] #3073695
09/02/22 09:39 PM
09/02/22 09:39 PM
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Originally Posted by 71birdJ68
Lets get back on topic, why did some cars have these wires and others didn't.


You were given that answer.

Re: Electrical Gurus [Re: 71birdJ68] #3073710
09/02/22 10:31 PM
09/02/22 10:31 PM
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Maybe someone after buying the car put it on later.
No one on here has heard of it or seen one on any car so far work work
The only fuse able link or safety wire I have heard of on any Mopar up through 1974 had them on the main starter battery relay feed from the starter main battery cable scope shruggy


Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: Electrical Gurus [Re: 71birdJ68] #3073734
09/03/22 02:09 AM
09/03/22 02:09 AM
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Originally Posted by 71birdJ68
Lets get back on topic, why did some cars have these wires and others didn't.


Some applications needed a certain-resistance in a portion of a circuit.
Adding a high-resistance wire will accomplish that.
Usually a nickel conductor type wire: i.e. fusible wire.
Certain models used such a wire in rear defroster circuit, believe some a-bodies..
It introduced a voltage drop (along it's path), thus lower voltage (speed) at the defroster motor terminals.
Same reason you see resistors hanging off 3-speed wiper switches.

Re: Electrical Gurus [Re: Cab_Burge] #3073759
09/03/22 08:42 AM
09/03/22 08:42 AM
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Originally Posted by Cab_Burge
Maybe someone after buying the car put it on later.
No one on here has heard of it or seen one on any car so far work work
The only fuse able link or safety wire I have heard of on any Mopar up through 1974 had them on the main starter battery relay feed from the starter main battery cable scope shruggy


Not true. I have seen them. For what its worth they are not needed. Most thought they were some type of extension wire not a resistor wire. These were a 2 year only part as I recall. 70-71 e-body and 71 b-body. Were used with the hemi and 6 pack 440. The cars gauge and senders were the same no mater what motor. The hemi and 6 pack 440 must of made more oil pressure so the resistor wire was added to keep the gauge in the normal range. However with that wire the gauge would read lower through out the whole range. There is no mention in the FSM that I have seen and they are listed in the parts manual. I posted the part number and I also posted a link with one that was sold. I do not know what more the poster of this thread needs to hear.

Re: Electrical Gurus [Re: Cab_Burge] #3073761
09/03/22 08:53 AM
09/03/22 08:53 AM
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Phila. Pa.
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Originally Posted by Cab_Burge
Originally Posted by Sinitro
Originally Posted by Cab_Burge
the gauges have -5 volts to them to make them read the ohms, not to the senders scope


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... wink
Looking closely at your diagram there are no wires, voltage supply, hook to the indicator needle, correct scope
That being so the coils read the ohms from the sender and pull the needle towards them when they have the highest or lowest ohms to make them work like a magnet, correct

Incorrect.
Chrysler's Tech explains how it works here: http://www.web.imperialclub.info/Repair/Lit/Master/227/Page01.htm

Re: Electrical Gurus [Re: Mattax] #3073762
09/03/22 08:56 AM
09/03/22 08:56 AM
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Or for those who prefer audio - visual.
Here's the fillmstrip that accompanied the booklet.

Re: Electrical Gurus [Re: NITROUSN] #3073777
09/03/22 10:07 AM
09/03/22 10:07 AM
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71birdJ68 Offline OP
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My car is a 383 car and it has one, also the FSM clearly shows it in the engine wiring digram, it even says resistance wire.

Re: Electrical Gurus [Re: 71birdJ68] #3073780
09/03/22 10:25 AM
09/03/22 10:25 AM
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Originally Posted by 71birdJ68
My car is a 383 car and it has one, also the FSM clearly shows it in the engine wiring digram, it even says resistance wire.


Ok so some how it has one whats the big deal? It either was a factory blunder or some one added it. Either way so what. If it were me I would run without it. If it was a by the numbers and a full restoration of a Hemi or 440 six pack I would leave it. In the FSM i only looked under diagnosis and it made no mention that I found. In the wiring diagram I will bet it mentioned HP and hemi cars. Unless you followed that car its whole life from the day it was born you will never know.

Re: Electrical Gurus [Re: NITROUSN] #3073804
09/03/22 11:32 AM
09/03/22 11:32 AM
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No big deal, but no body can explain its purpose. It’s not a factory mess up cause the wire coming out of the harness has to match the connector of this wire, Where usually a wire comes out of the harness and goes straight to the sending unit. I can state that the car has not been messed with before. If the picture loaded, this is the wire. I’ll try it with and without, I’m bringing it up cause this is some forgotten mopar thing that nobody knew about, even the experts.

A7D843B9-F75D-4D0A-9BF5-F5F3076616A2.jpeg9B63DF0D-0EFB-4CBF-BEEF-14B8A6101723.jpeg
Last edited by 71birdJ68; 09/03/22 11:35 AM.
Re: Electrical Gurus [Re: 71birdJ68] #3076009
09/10/22 10:34 AM
09/10/22 10:34 AM
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It is interesting subject. My 70 383 b body RR has added mechanical gauge along with the pressure unit for the instrument panel. All original to the car. My water temp readys very accurately as it rises from cold to 180. My pressure gauge rises to 20 psi and hovers there, while the mechanical is around 50 psi. Idle or high rpm the mechanical changes, the electrical does not. I think I am going to try changing the sender to see if it changes how the electrical works.

But for the OP ? It doesn't make sense to me.

The oil pump for a 440-6 or hemi was the same big block pump except it had a heavier relief valve spring so bypass did not occur until a higher pressure. The sender called for is common through the years, but the 7-71 parts book calls out this added harness for 440-6 and hemi only, yet the gauge would be the same for a 383. Adding a resistor to prevent pegging ok, but that means your gauge is offset in value and does not accurately present pressure. Even so a hemi or 6pack should not have much higher pressure unless the motor spec were much tighter to give less leakage. Which I don't think they were. Are we to believe ralley gauges are motor specific? I don't think they are.

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