Oil Pressure Sender... Frustrations....
12-20-2003, 06:49 PM
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Oil Pressure Sender... Frustrations....
For some background, I have done a Sr-5 gauge swap and haven't gotten the new oil pressure sending unit. So I had the wire unhooked and just haven't needed to change the oil so I hadn't bought and installed the new gauge.
Ok, took my truck in to have the clutch replaced. While my friend was replacing it he checked a few other things out for me a let me know about them. I didn't remember to let him know not to hook up the oil pressure sender. So he ended up hooking it up.
My question is, and I'm probably going to get the same answer that is in my head, Is the oil pressure gauge on the cluster screwed? I know its said time and time again not to hook up the old sender when you do the swap but I'm just curious if there is a thread of hope that its not burnt out.
Ok, took my truck in to have the clutch replaced. While my friend was replacing it he checked a few other things out for me a let me know about them. I didn't remember to let him know not to hook up the oil pressure sender. So he ended up hooking it up.
My question is, and I'm probably going to get the same answer that is in my head, Is the oil pressure gauge on the cluster screwed? I know its said time and time again not to hook up the old sender when you do the swap but I'm just curious if there is a thread of hope that its not burnt out.
02-11-2004, 06:11 PM
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Not yet, I just got the oil pressure sensor the other day so I gotta get some time to install it. Then I'll be able to test it and figure out what I'm going to do. I'm pretty sure its fried though.
02-11-2004, 06:17 PM
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i just completely for got about unhooking the wire....i was worried bout having a factory tach wire already ran and forgot all about it...thought about it this morn on my way to work...just outta the blue it clicked that i didn't unhook that wire...and it's been like a month since i installed the cluster...if it is messed up does neone know how to fix this?
thanks
hub
thanks
hub
02-11-2004, 06:33 PM
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Aside from a new gauge i don't think that there is a way to fix it. I think there was some talk on 4x4wire about it but I didn't look into it too far because I haven't hooked up the new sender yet.
02-11-2004, 06:46 PM
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lemme know what happens after you install the sender...i got a sender but have been waitin til time to change the oil to install it...i'm not quite there yet but i'm thinking about goin and ahead and changing it just to see....
later
later
02-11-2004, 07:03 PM
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Jeez, with friends like that you don't need enemies.
Have you tried the boneyards yet?
With my '88 PU, some early '80's Cressida's had the same oil-pressure gauge, tach-drive assembly, and coolant-temp gauge as the '84-'88 SR5 truck cluster.
I'm not sure about the '89-'95 PU's though.
Have you tried the boneyards yet?
With my '88 PU, some early '80's Cressida's had the same oil-pressure gauge, tach-drive assembly, and coolant-temp gauge as the '84-'88 SR5 truck cluster.
I'm not sure about the '89-'95 PU's though.
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02-12-2004, 12:56 AM
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Originally posted by Krash
Aside from a new gauge i don't think that there is a way to fix it. I think there was some talk on 4x4wire about it but I didn't look into it too far because I haven't hooked up the new sender yet.
Aside from a new gauge i don't think that there is a way to fix it. I think there was some talk on 4x4wire about it but I didn't look into it too far because I haven't hooked up the new sender yet.
02-12-2004, 05:14 AM
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yea, mine did vary when i first installed the cluster....sometimes on the L and sometimes it'd rise and stay on the H. now it just stays on the H. even after i unplugged the wired. foxtrapper, i hope you're right...but it sounds like krashes luck is like mine, not too good..
so it's possible to just replace the oil pressure gauge if it's indeed broken?
later
hub
so it's possible to just replace the oil pressure gauge if it's indeed broken?
later
hub
02-12-2004, 07:20 AM
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Lets go through how the two systems work, so you'll understand why it's not going to destroy a guage to connect it to the idiot light sending unit.
With the idiot light system the sending unit is merely a pressure switch. With oil pressure, the switch is held open. With no oil pressure, the switch closes, and the circuit is closed. Electricity flows through the dashboard light, down the wire, through the closed switch, and into the block for ground. The sending unit is merely a toggle switch.
With the gauge system the sending unit is a variable resistor connected to a bellows. As oil pressure goes up, the bellows expands, sweeping the contact over the resistor track. Resistance is inverse to pressure. Ie, the more the oil pressure goes up, the lower the resistance. When there is no oil pressure, the bellows pulls back and resistance goes up to infinity. In fact, it usually breaks contact.
So the dashboard gauge has electricity provided to it, and it goes through the gauge, down the wire, to the sending unit, and to ground. When the engine is off there is no oil pressure, resistance is high, and the gauge reads zero. With the engine running, there is oil pressure, resistance goes down, and the gauge reads something.
It's a common and acceptable test of the gauge to simply ground the wire and observe the gauge reading. From this test, the gauge should read somewhere upwards of its maximum range.
So what happens when you connect a dashboard gauge to an idiot light sending unit? With no oil pressure the sending unit grounds, and the gauge reads maximum pressure. With the engine running and oil pressure built up, the sending unit switch opens, no current flows, and the gauge reads zero oil pressure.
Now at this point you may say "that's not what mine did". Many times the sending unit is filthy with oil, both inside and out. So there is some current flow through the mess, resulting in a partial reading with oil pressure (switch open). It also can partially block the clean ground when the switch is closed from no oil pressure (engine off), resulting in a less than full sweep of the gauge.
And that's why I'm saying you're not going to damage the gauge by connecting it to the idiot light sending unit.
As for the connector, the metal connector is the same. You can swap the plastic cover if you wish by merely depressing the locking tab and switching it. Both are a side position slide on type.
With the idiot light system the sending unit is merely a pressure switch. With oil pressure, the switch is held open. With no oil pressure, the switch closes, and the circuit is closed. Electricity flows through the dashboard light, down the wire, through the closed switch, and into the block for ground. The sending unit is merely a toggle switch.
With the gauge system the sending unit is a variable resistor connected to a bellows. As oil pressure goes up, the bellows expands, sweeping the contact over the resistor track. Resistance is inverse to pressure. Ie, the more the oil pressure goes up, the lower the resistance. When there is no oil pressure, the bellows pulls back and resistance goes up to infinity. In fact, it usually breaks contact.
So the dashboard gauge has electricity provided to it, and it goes through the gauge, down the wire, to the sending unit, and to ground. When the engine is off there is no oil pressure, resistance is high, and the gauge reads zero. With the engine running, there is oil pressure, resistance goes down, and the gauge reads something.
It's a common and acceptable test of the gauge to simply ground the wire and observe the gauge reading. From this test, the gauge should read somewhere upwards of its maximum range.
So what happens when you connect a dashboard gauge to an idiot light sending unit? With no oil pressure the sending unit grounds, and the gauge reads maximum pressure. With the engine running and oil pressure built up, the sending unit switch opens, no current flows, and the gauge reads zero oil pressure.
Now at this point you may say "that's not what mine did". Many times the sending unit is filthy with oil, both inside and out. So there is some current flow through the mess, resulting in a partial reading with oil pressure (switch open). It also can partially block the clean ground when the switch is closed from no oil pressure (engine off), resulting in a less than full sweep of the gauge.
And that's why I'm saying you're not going to damage the gauge by connecting it to the idiot light sending unit.
As for the connector, the metal connector is the same. You can swap the plastic cover if you wish by merely depressing the locking tab and switching it. Both are a side position slide on type.
02-12-2004, 05:39 PM
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Originally posted by Krash
Yeah, I can't justify changing my own oil yet (to do the sender)....
Yeah, I can't justify changing my own oil yet (to do the sender)....
foxtrapper,
That's an pretty good explaination on the function of both sensors and why the idiot sensor won't blow out the SR5 cluster oil-pressure gauge.
However, have you actually tried hooking up the standard switch to the SR5 cluster and then going back to the proper sending unit just to make sure?I'm just trying to figure out how the "it'll blow your gauge" rumor got started on here. You'd think someone would've tried using the variable sending unit with their SR5 cluster after having it hooked up to the idiot sender just to be sure the gauge actually still worked or not.:pat:
02-13-2004, 02:05 AM
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Yes, I did it when I installed the SR5 dash into my 86. Hooked it up temporarily for a few days until I got around to buying a new sending unit.
Rumors and myths abound. From the need of having back pressure in exhaust systems to claims that lack of thermostats causing the coolant to move to fast to work.
Rumors and myths abound. From the need of having back pressure in exhaust systems to claims that lack of thermostats causing the coolant to move to fast to work.
Originally posted by mikedog
You don't need to change the oil to do the sender. Just use some teflon tape or compound on the threads before you put it in.
foxtrapper,
That's an pretty good explaination on the function of both sensors and why the idiot sensor won't blow out the SR5 cluster oil-pressure gauge. However, have you actually tried hooking up the standard switch to the SR5 cluster and then going back to the proper sending unit just to make sure?
I'm just trying to figure out how the "it'll blow your gauge" rumor got started on here. You'd think someone would've tried using the variable sending unit with their SR5 cluster after having it hooked up to the idiot sender just to be sure the gauge actually still worked or not.:pat:
You don't need to change the oil to do the sender. Just use some teflon tape or compound on the threads before you put it in.
foxtrapper,
That's an pretty good explaination on the function of both sensors and why the idiot sensor won't blow out the SR5 cluster oil-pressure gauge.
However, have you actually tried hooking up the standard switch to the SR5 cluster and then going back to the proper sending unit just to make sure?I'm just trying to figure out how the "it'll blow your gauge" rumor got started on here. You'd think someone would've tried using the variable sending unit with their SR5 cluster after having it hooked up to the idiot sender just to be sure the gauge actually still worked or not.:pat:
02-14-2004, 06:42 AM
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Originally Posted by Krash
Yeah, its a myth mine works fine, I hooked up the new sensor today and nothing is wrong with the gauge cluster.
thanks
hub
02-14-2004, 09:21 AM
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Buddy, it is a pain in the ass to get too. I can't remember whether I used an 1 1/4 or 1 1/2 socket to take the dummy light sensor off, not to mention with a really long extension. . All I can remember is I was about to leave and my next door neighbor happened to come over wondering if I wanted to buy a Warn 8000 from one of his friends. The new sensor I just put some teflon tape on, 15mm open end wrench if I remember right, and tightened it up. Pretty simple, the hardest part was finding a socket to fit it.
Last edited by Krash; 02-14-2004 at 09:22 AM.
02-15-2004, 09:50 AM
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Krash, did you have any trouble with the tape on the new sender? I was told to stay away from taping it because it would break the ground that it gets from touching the block... Overall though, I wish I had used something like tape or something similar because I ended up installing the wrong sending unit (auto parts store gave me the wrong one) and in trying to take it out, it broke off in the side of my block 
! So now I'm basically SOL :-(
! So now I'm basically SOL :-(
02-15-2004, 10:29 AM
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Newp, used some teflon tape and it seems to be working fine. I got one from an autoparts store also but its made by nippondenso so I'm not really worried about something breaking off or not fitting.
