Low Oil Level Relay June 05, 2017, 09:50:11 PM Ive been working on getting everything working on my 87 TC but this relay has me scratching my head. Its not a standard relay and appears to possibly be some sort of intrinsic safety device. My electronics abilities is amateur at best and I cant find any info about these old Motorola components to see how to go abouts testing. I will try to post a pic of the internals. The only physical suspicious component is a 1N4148 diode that looks a little melted but intact. I need to remove it for testing to be sure.I have verified the wiring, the bulb tests out when key is turned but grounding the sender wire fails to activate the light. I even jumped the wire right at the relay to ground and nothing. What I did find odd is having battery voltage on the sender wire if this is truely some sort of safety device. Again thats my ignorance as to how this thing actually works.I suppose theres a question in here......looking at Pg 143 in the 88 EVTM, can anyone see any reason I cant use a standard relay in place of this device. It would appear to be redundant to switch a relay for the ground signal since control power is coming from the same circuit as the bulb. But I suppose I could fuse the relay separately for added protection. Ideally I would like to use this device and will likely try to source one locally. I know its something most people can do without but ever since my Turbo oil drain let go I would like a little bit of warning if it happens again........LOL it let out a puff of smoke from under the hood and a puddle on the garage floor. Good thing not on the highway where I may not have noticed the plume burning off the exhaust behind me.Heres the internals. Note the diode upper left below the resistor.John Quote Selected
Low Oil Level Relay Reply #1 – June 05, 2017, 09:59:43 PM Here's the picture again if you can't see it in the first post. I couldn't when viewing from my phone.Funny I cant see this one from my computer???? Quote Selected
Low Oil Level Relay Reply #2 – June 05, 2017, 10:55:32 PM Low oil level indicator is all but useless, it only illuminates BEFORE engine is started, IF level is low... It'll never come on while running...I can't see any pict either... Quote Selected
Low Oil Level Relay Reply #3 – June 06, 2017, 07:29:30 AM Interesting..... I have to go back into the EVTM and see if there's a description of operation. Makes no sense to have it light before start up only considering bulb prove out happens when key is turned to crank. Makes it a little confusing. I wasn't able to make it light key on position with the trigger grounded.John Quote Selected
Low Oil Level Relay Reply #4 – June 06, 2017, 10:44:01 AM Well it should light at ign on if wire to pan sensor is grounded...The sensor in pan is a caged float that makes contact with cage if oil is below a certain level(I'm guessing approx 1.5qt)... When engine is running there is a quart or more circulating in engine, so level would already be near the "trip" level... Combine that with the crank whipping the oil in pan at 3000+ RPMs and the light would be on all the time... It's something that went away on mine when I did the 5.0 swap in '99...Only time I've had one actually activate was if oil was approx a qt low and car was parked on angle, with left side high... Quote Selected
Low Oil Level Relay Reply #5 – June 06, 2017, 04:22:58 PM I ways call that the the one quart to go until you are two low on my cars. Doesnt make sewing machine noises until its two quarts low. Quote Selected
Low Oil Level Relay Reply #6 – June 06, 2017, 07:41:58 PM I don't know if it's normal but it appears to work after all. It doesn't work like a normal switching relay but instead it seems you need to wait with key off and signal grounded. Upon turning key back on the warning light comes on and stays on regardless of removing the signal ground untill next restart....then light is offActually found this by accident. I was in the garage working on finding the problem when the wife called me in for dinner. I turned the key off and left the signal grounded. Went back out to continue, turned key on...the stupid light turns on. My first thought was oh wtf did I do. Removed my ground jumper WTF still on. Turned key off then back on.....the light was off. That got me thinking about Turbocoupe50's earlier post about only illuminating pre-start I was able to reliably get the light to come on by just waiting with key off for a couple of minutes.If this doesn't sound normal.....please let me know otherwise I will consider it fixed! I may still experiment with a regular relay to see how much chattering there is with real-time monitoring.ThanksJohn Quote Selected
Low Oil Level Relay Reply #7 – June 06, 2017, 08:10:50 PM Quote from: Skunk;461187I don't know if it's normal but it appears to work after all. It doesn't work like a normal switching relay but instead it seems you need to wait with key off and signal grounded. Upon turning key back on the warning light comes on and stays on regardless of removing the signal ground untill next restart....then light is offActually found this by accident. I was in the garage working on finding the problem when the wife called me in for dinner. I turned the key off and left the signal grounded. Went back out to continue, turned key on...the stupid light turns on. My first thought was oh wtf did I do. Removed my ground jumper WTF still on. Turned key off then back on.....the light was off. That got me thinking about Turbocoupe50's earlier post about only illuminating pre-start I was able to reliably get the light to come on by just waiting with key off for a couple of minutes.If this doesn't sound normal.....please let me know otherwise I will consider it fixed! I may still experiment with a regular relay to see how much chattering there is with real-time monitoring.ThanksJohn That sounds about right, according the description in the 88 EVTM page 144. With the ignition in Start, the light is turned on by a separate circuit from the ignition switch through a diode to the light. This is the light bulb test. With the ignition in Run, the light is turned on by the solid state(latch type) relay if the level switch is closed. (low on oil).The latch relay also has a long delay before it resets after key off. Quote Selected
Low Oil Level Relay Reply #8 – June 06, 2017, 09:08:56 PM Quote from: Haystack;461184I ways call that the the one quart to go until you are two low on my cars. Doesnt make sewing machine noises until its two quarts low.LOL reminds me of gal who visits next door... One day she had the hood open on her old Durango, said she was listening for a knock.. Trish next door says "maybe oil is low", to that she replies " no this isn't my low oil knock, it's something else"... Turned out to have a busted flexplate, she junked it...My '96 F-150 was like 4+ quarts low when I got it, old 5.0 was quiet as a church mouse... Never made first click, tick, tap, nothing... I didn't know it was low till I pulled the drain plug and it didn't much more than wet bottom of drain pan... I figured well this thing is junk, five years later it still runs great and uses maybe a quart in 2500 miles... Quote Selected
Low Oil Level Relay Reply #9 – June 07, 2017, 12:09:03 AM When I rebuilt the 5.0 in my car 10 years ago I removed the low oil sensor from the oil pan. The things leak and are pretty useless if you regularly check your oil. I don't miss it. Quote Selected
Low Oil Level Relay Reply #10 – June 07, 2017, 10:27:31 AM Softtouch.....thanks for putting that up.....saved me a little time going through the PDF. Man I really need to print a copy. I so much prefer paper when flipping between several pages.Ya I've contemplated removing the sender many times but decided to keep it due to tapping the flimsy pan for my oil return. Next time it's off I'm welding or silver soldering the fitting on. Besides you can't have a 5.0 that doesn't mark it's territory. John Quote Selected
Low Oil Level Relay Reply #11 – June 07, 2017, 10:58:58 AM For those couple months i had the new explorer style pan gasket in my car, it was so weird. I learned most of my oil leak was actually power steering. I just dumped a bottle in it for safety and got passed as an advise for leaks 5 years in a row.Btw, as long as it doesnt make bottom end noise from a lack of oil, you are still golden. I bent my disptick when i did my pan (probably why it was so hard to get out and back in) and it was rubbing on the side of the block giving me a false low reading. The top end kept getting worse and worse till i was sure the engine was gone. I decided to dump 5 quarts of 15w45 in it and actually check the dipstick, found it was bent really bad. Fired it up and it was like new. Think i got another 10k or so out of it before busting the oil pan again off roading. Its right around 350k miles and not worth another $50 for the pan an 12 hours to get it in. Laying under a car ontop of engine puller legs sucks. Quote Selected
Low Oil Level Relay Reply #12 – June 07, 2017, 12:24:43 PM Quote from: Skunk;461200Softtouch Next time it's off I'm welding or silver soldering the fitting on. Besides you can't have a 5.0 that doesn't mark it's territory. JohnYou can have a 5.0 that doesn't leak, my old F150 has yet to drip a drop of oil, or anything else for that matter... It's a major surprise, not many vehicles 21 years old and almost 200K miles can claim that... Was no doubt all but dry of oil when I got it because it hadn't been checked or changed in probably 15K miles... Quote Selected
Low Oil Level Relay Reply #13 – June 07, 2017, 01:01:54 PM Lol....you can't leak if there's nothing to leak.IMine is actually pretty good depending on what oil I'm running. 10w30 seems to get past the rear main if I'm running hard WOT full boost. Engine was freshened a couple years ago but it didn't take long to start dripping. If I'm easy on it with the occasional smashed throttle..... Not a drop..... of course it's hard to tell when previous hard runs are rustproofing the underside. I really think if I could improve my current pan-evac PCV system I could stop blowing past the seal. Not an easy task with a blow through MAF arrangement.John Quote Selected
Low Oil Level Relay Reply #14 – June 07, 2017, 01:12:32 PM Quote from: Skunk;461204Lol....you can't leak if there's nothing to leak.JohnVery true but for the last five years it's never been below a qt low... Quote Selected
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