Low oil pressure sender on HD6G
Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Construction and other equipment
Forum Description: everything else with orange (or yellow) paint
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=156797
Printed Date: 21 Aug 2025 at 8:29pm
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com
Topic: Low oil pressure sender on HD6G
Posted By: Leop
Subject: Low oil pressure sender on HD6G
Date Posted: 29 Dec 2018 at 10:36pm
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While im waiting for my manuals, or a posted wiring diagram i was wondering if anyone knew where the output of the low oil pressure swich goes. This switch is mounted on a T that screws in right at the oil pressure gauge. The switch is round with two screw terminals on the top. One of the terminals is connected to power(negative side of batttery) and the other terminal is connected to a wire that descends toward the engine compartment where it terminates with a buch of rat bite marks. No sign of the other side of the wire. I assume the rat took it  Does the switch cause a valve to cut fuel to the motor? If so i assume its bypassed durring cranking? Or is there a flapper valve to cut off air? Or perhaps just a horn of some type? Leo |
Replies:
Posted By: AC Mel
Date Posted: 29 Dec 2018 at 11:11pm
| Leo..Can you post some pictures? Do you know the serial #? or year model? Not sure but the oil pressure switch is probably the one that activates the charging system...nothing to do with the fuel system. Fuel system should be a manual shut off. |
Posted By: Leop
Date Posted: 30 Dec 2018 at 1:03am
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Sure, in the morning ill take some pictures. Where can i find the serial number? |
Posted By: AC Mel
Date Posted: 30 Dec 2018 at 9:55am
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Serial # could be on a plate on the dash below all the gauges....if it hasen't been removed. Is also stamped into the right rear side of the case below the bottom of the fuel tank...that one has not been removed...but may or may not be visible depending if there is an attachment..winch or rippers etc. If there is nothing on the back it should be easy to find |
Posted By: Leop
Date Posted: 30 Dec 2018 at 12:49pm
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Hi Mel, Can you tell me more about this charging system? I have never heard of a charging system that's gated by oil pressure. Did it simply delay charging until the motor was up and running? Did it disconnect the batteries through a relay to prevent them discharging by back feeding through the generator? Was it a direct tap to tell the regulator actual voltage at the batteries so as to prevent the voltage regulator from being fooled by voltage drop across the high current wiring? Was it for sourcing power for an excitaion voltage to the generator? No one has posted a wiring diagram yet, so need to wing wiring "her" today on my own and it would be nice to know what that darn wire does, or more accurately stated, used to do? Note to gals and the PC crowd. I have decide the tractor is a her because it did not come with a manual or directions, same as my wife 
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Posted By: Jim.ME
Date Posted: 30 Dec 2018 at 1:39pm
| The switch on the tee at the back of the oil gauge is to operate the hourmeter. You can view the parts book on line at http://www.Minnpar.com" rel="nofollow - www.Minnpar.com . Click on parts books, select crawler loaders, then Allis and Fiat, You should find the 6G parts book there. Looks like you may want to have your serial number in hand. |
Posted By: Leop
Date Posted: 30 Dec 2018 at 1:48pm
| Jim, you are a God. My wife thinks so too, as does the propane man. |
Posted By: Leop
Date Posted: 30 Dec 2018 at 2:19pm
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Jim, You are still a god, but the link seems to show a teaser manual. Pages 1-6 and then jumps to page 66 and the cuts off a few pages later. Am i looking at the right manual. It says "service manual" on the cover, and you said "parts manual" in you post so im thinking i might have gotten it wrong. |
Posted By: Leop
Date Posted: 30 Dec 2018 at 2:26pm
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Never mind Jim. I found the right parts book now. Thanks again. Sincerely, Leo |
Posted By: Jim.ME
Date Posted: 30 Dec 2018 at 2:44pm
| I believe you will have to purchase a service manual unless someone has one they chose to give you. There are not many free, downloadable service or operator manuals for most equipment. |
Posted By: Ray54
Date Posted: 30 Dec 2018 at 9:11pm
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If you can get to a parts book on line check and see if it was not a generator rather than alternator when new. If it started with a alternator it could be part of that,because older alternators needed to be excited to get them charging. Running power to a oil pressure switch "automated the system", to get it started and not having a switch to close to keep from draining batteries when not running. |
Posted By: Jim.ME
Date Posted: 30 Dec 2018 at 9:23pm
| Parts book shows the switch is for the hourmeter. Original equipment appears to be 24 volt generators in the parts book, when checked against the Delco numbers. |