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Author Topic: Griff's Project #1 (aka MLP)  (Read 11323 times)
Griff in Fairbanks
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« Reply #45 on: September 17, 2011, 10:57:55 PM »

I would go with separate circuits for oil pressure. The combined units like on my 96 pickup are notorious for being inaccurate as far pressure readings.
For temp. sensor how about the water pump bypass hose. It has flow at all times. Heater hose wouldn't if you had heater temp control off.
I don't know of any one doing that with the water temp. gauge, just an idea that popped into my head,
The oil pressure units are separate circuits.  The switch (on/off) and sensor (variable resistance) are independent, other than being together in a single unit.

Electric gauges are, at best, approximate.  They are actually voltage gauges and the sensors vary the voltage to the gauge by varying the resistance.  Longer/shorter and/or larger/smaller wires can affect the voltage sensed by the gauge by changing the resistance in the circuit.  More importantly, an inadequate ground can throw off the gauge's reading by increasing the resistance on the negative (ground) side of the circuit.  Since most older switches and sensors, and the new oil pressure units, use the engine for a ground, a loose or corroded ground connection for the engine will throw the gauge off.  (That's why you should NOT use thread tape on the sensors ... accept a little leakage or use thread compound sparingly.)

It's easy to check, though.  Run a jumper from the base of the sensor to the battery's negative terminal.  If the gauge reading changes, you know you have an inadequate ground.

It's worth noting the engine's computer only cares whether there is or is not enough oil pressure so the computer uses the switch (on/off) side of the unit.  The sensor (variable resistance) side of the unit is solely for the gauge that gives your typical driver the impression they know what's going on.  If the computer senses inadequate oil pressure, it stores the information as a code and turns on the Check Engine light.  The Check Engine light effectively combines the "big three" idiot lights (oil pressure, engine temperature, and voltage), along with other abnormal conditions, into a single idiot light.  Unfortunately, you need a technician's tools (i.e., a code reader) to actually tell what's happening.

In the case of non-computerized engines, the switch side of the oil pressure unit can be used to provide a warning (buzzer and/or indicator -- idiot -- light) in the event of a catastrophic drop in oil pressure.

Engine temperature sensors are a different case compared to oil pressure sensors.  The computers actually use changes in engine temperature to adjust engine performance so they require the variable resistance.  As far as I can tell, no newer vehicles use engine temperature switches and the switches are actually getting hard to find, even for older vehicles.  A buddy at work, who specializes in Ford engines, and I spent two hours looking for switches for older Fords and Dodges that we knew came with idiot lights.  In every case the company's computer only showed gauge-type sensors.  The application sections in the books did likewise, with neither providing any listing for engine temperature switches.  We had to dig into the section that listed all sensors in part number order before finally finding the applicable switches.  (And, yes, I ordered and received the switch used on early 70's and older Dodge engines.)

Obviously, I haven't been able to find a combined engine temperature switch/sensor unit and am convinced they don't exist.  Because I like the idea of two separate monitor circuits, I'm going with a sensor for the gauge and a separate switch for warning of a catastrophic rise in engine temperature.

BTW - because the computer needs a relatively accurate measure of engine temperature to adjust performance, most newer temperature sensors have gotten away from using the engine for ground and typically have a second terminal for the ground (negative) side of the circuit.  (The Neon sensor a customer was looking for, which kick-started this investigation, has three terminals but I can't find anything that says why there's three or what each one does ... because Neon engines are a wee bit different from LA small blocks, I decide not to pursue that possibility.)

Charlie, the bypass hose is a GREAT suggestion.  Unfortunately, the bypass hose has a 1" inside diameter and Autometer's adapters are sized for 5/8", 3/4", 1-1/4" and 1-1/2" ID hoses.  But, I like your suggestion enough to seriously consider machining a custom adapter for 1" ID hoses.

Finally, I'm also looking at a warning light for low voltage, in addition to a volt meter.  Right now, I'm looking at circuits for LED-type volt meters and simply eliminating all the LEDs except the one that indicates low voltage.
« Last Edit: September 17, 2011, 11:01:11 PM by Griff in Fairbanks » Logged

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Griff in Fairbanks
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« Reply #46 on: September 17, 2011, 11:13:55 PM »

Oh, yeah, a couple of other things ...

The front brake pads (finally) came in ... I had to order them twice.  The first time, the Anchorage warehouse actually had zero sets where the computer said they had one set so they cancelled the order.  Then, the computer said the Seattle warehouse had several sets and they apparently had at least one set, because they sent a set up on the barge.

Also, as if I'm not busy enough, it looks like my son-in-law and I may be starting a business.  Tentatively named Riffgan Restorations, we'll be doing powder coating, electrolytic rust removal, and small-to-medium parts restorations.  (Nobody in interior Alaska does powder coating and everyone gets excited when I mention that I do it for myself ... all the automotive painters are urging -- puuushing -- me to do it commercially.) If we do it,  I'll provide the shop, tools, etc. and he'll be primarily running the show.
« Last Edit: September 17, 2011, 11:17:39 PM by Griff in Fairbanks » Logged

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Griff in Fairbanks
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« Reply #47 on: January 19, 2012, 03:34:55 PM »

Found new brake rotors through work and have a pair on non-stocking backorder.

Boss and I went 'round 'n' 'round a couple of months ago trying to find these through CarQuest and every listing was for the R-300 brakes, which have single piston calipers.  He even ordered up one of the rotors so we could compare it to my rotors.  (He didn't believe me when I told him it was the wrong one.)  We finally gave up and decided we'd just go through all the work of reconditioning the rotors I have, which are heavily rusted but still have enough "meat" to be turned.

Then, last Thursday, I was wandering through carquest.com to see what I could find that I couldn't find through the computers at work.  (I've already proved I can find stuff at home that I can't find on the store computers ... )  I ran across some online catalogs for medium- and heavy-duty trucks that we can't get at through the work computers and, near the end of one of the catalogs was a listing for rotors that showed an interchange for the Kelsey-Hayes part number stamped in my rotors.  The next day, at work, I showed the boss a print-out of the catalog, showed him we couldn't get at the catalog from work, entered the CarQuest part number in the work computers, and put the rotors on order.

The boss's sarcastic response was, "I might as well have you work from home from home," because we've run into this situation before.  He's especially annoyed at the corporate bureaucracy because (1) we've run into this situation before, (2) the company sent one of my coworkers to Anchorage for a week of training in medium- and heavy-duty truck parts, (3) we haven't been allowed to stock medium- and heavy-duty parts we know our customers need regularly, and (4) have been told we can just look up our customers need and order them from the Anchorage warehouse.

BTW - the CarQuest part number is 666-13882.

Meanwhile, I've been researching "phosphate and oil" finishes, sometimes called "P & O" finish.  This is the finish used on many new and remanufactured parts, such as brake calipers.  It's a messy and smelly process but not otherwise difficult, unusually dangerous, or expensive.  Basically, once all the grease, crud, and rust have been removed, you soak the part in mixture of phosphoric acid and manganese dioxide, heated to 195 degrees, rinse the part in clean water, drench it in WD-40, and finish it with an oil containing a rust inhibitor.  (Probably Marvel Mystery Oil.)

Now, I'm just waiting for the weather to warm up enough to do it outside.

As of right now, I have everything lined up to restore the front axle (and other parts) to "new or better condition."
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« Reply #48 on: January 19, 2012, 05:45:59 PM »

Glad to hear you figured it out - and not surprised at the SNAFU with the company computers.

 Wink
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1973 Concord 20' Class A - 440/727
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