BlownCorona Posted March 4, 2015 Share Posted March 4, 2015 hello all i recently installed 3x gauges in my corona. volts, water temp and oil pressure. everything seems okay with them, except they read higher on the scale the more electrical load is drawn from the system. ie lights on,heater on, indicators,brakes,wipers etc. a small combonation can max out the water temp gauges aswell. now i have a pretty good understanding of this kinda stuff, but its not excellent, and this one has got me a bit confiused. at first thought it seems like the power source is fluctuating in voltage, changing the reference voltage. however these gauges work of measuring resistance, so im not really sure whats going on, or how to fix it. any insight would be great! Quote Link to comment Share on other sites More sharing options...
Nominal Posted March 4, 2015 Share Posted March 4, 2015 Instruments usually work off a regulated voltage. As the sensor is a resistance, the meter is probably indicating current, so as the car battery voltage changes (charging/load/engine rpm etc) the reading will fluctuate. No idea where you would get the correct voltage on a Corona. Are the gauges new and specced for 12V? Some work on 5V maybe? Something like this would get you a 12v supply (so long as the actual car voltage is >13v) http://www.jaycar.co.nz/productView.asp?ID=ZV1564 Quote Link to comment Share on other sites More sharing options...
BlownCorona Posted March 4, 2015 Author Share Posted March 4, 2015 They are brand new gauges, for cars. Not expensive ones, but they are trisco which have been around for years so they can't be too bad. Quote Link to comment Share on other sites More sharing options...
downtrail Posted March 4, 2015 Share Posted March 4, 2015 Bad ground connection to engine / senders if they are grounded sensors. If above ground check that where youve grounded them to is sufficient oe resistance from that ground to battery neg is below 1ohm 1 Quote Link to comment Share on other sites More sharing options...
Frosty Posted March 4, 2015 Share Posted March 4, 2015 I have one word. Earths. Have the gauges been out? The copper strips oxidise and never go back in just the right place. Give them scuff with some 320 grip sand paper then wipe down with thiners or petrol and reconnect. A film of grease on the newly cleaned contacts will keep them from oxidising again. 2 Quote Link to comment Share on other sites More sharing options...
BlownCorona Posted March 4, 2015 Author Share Posted March 4, 2015 Not factory gauges, but along the same point as down trail. I would have thought the water temp gauge would be earthed fine though. It's mounted with one of those alloy in hose blocks, and this has an earth wire directly to the battery neg terminal Quote Link to comment Share on other sites More sharing options...
downtrail Posted March 4, 2015 Share Posted March 4, 2015 Not factory gauges, but along the same point as down trail. I would have thought the water temp gauge would be earthed fine though. It's mounted with one of those alloy in hose blocks, and this has an earth wire directly to the battery neg terminal Is there copious amounts of thread tape on the sender? That will cause your issue. That or if its annodised they never make for great connections clean off around where youve lugged to. Check with meter from battery neg to the body of the sender if above 1ohm no good re do connections. I prefer to use loktite 567 for thread sealing over thread tape. Quote Link to comment Share on other sites More sharing options...
BlownCorona Posted March 4, 2015 Author Share Posted March 4, 2015 There is thread tape, and that's on the list to go as I did wonder. Oil pressure gauge has no tape and has same issue though. All gauges are wired in parallel from the same source, and earth to the same point. Also out of curiosity, the volt gauge should actually move with changes in draw yeah? (it does) Quote Link to comment Share on other sites More sharing options...
downtrail Posted March 4, 2015 Share Posted March 4, 2015 Shouldnt move much should see a difference from when ign on then running ie charging. Should see a small drop as you increse load but nothing dramatic. Quote Link to comment Share on other sites More sharing options...
BlownCorona Posted March 4, 2015 Author Share Posted March 4, 2015 Seems about right, it does get kinda low if I have everything on at once, but that's quite a lot of draw and a fairly big stereo. Quote Link to comment Share on other sites More sharing options...
h4nd Posted March 9, 2015 Share Posted March 9, 2015 Got a pic of where things are earthed? Are the guages / stereo sharing any wires? Quote Link to comment Share on other sites More sharing options...
BlownCorona Posted March 9, 2015 Author Share Posted March 9, 2015 gauges and stereo are sharing both power and earth. this be an issue? Quote Link to comment Share on other sites More sharing options...
AllTorque Posted March 10, 2015 Share Posted March 10, 2015 Probably Quote Link to comment Share on other sites More sharing options...
downtrail Posted March 10, 2015 Share Posted March 10, 2015 Run gauge earth to same spot as sender earth and report back Quote Link to comment Share on other sites More sharing options...
BlownCorona Posted March 10, 2015 Author Share Posted March 10, 2015 Will do. Quote Link to comment Share on other sites More sharing options...
ProZac Posted March 12, 2015 Share Posted March 12, 2015 Have you got a multimeter? With your extra electrical load turned on (lights and stuff), measure the voltage at the output stud of your alternator, and the positive terminal of your battery, interested to see what they are. Sounds like an earthing issue though. Make sure your main earths (battery to body, and engine block to body) are clean and tight. Quote Link to comment Share on other sites More sharing options...
Lump Posted March 14, 2015 Share Posted March 14, 2015 Have you got a multimeter? With your extra electrical load turned on (lights and stuff), measure the voltage at the output stud of your alternator, and the positive terminal of your battery, interested to see what they are. The voltage regulator on the alternator might be failing and overcharging - this happened on my motorbike and the temp gauge overread as its internal voltage regulator (12v down to 7v) couldn't handle the increased loads from the charging system. Do your gauges over read more when the engine is running faster? Quote Link to comment Share on other sites More sharing options...
BlownCorona Posted March 14, 2015 Author Share Posted March 14, 2015 I haven't noticed anything related to revs. But I did notice when I put the rebuilt engine in, the battery to body earth was left off. I haven't had a chance to make one up yet, but that can't be helping the situation Quote Link to comment Share on other sites More sharing options...
kempy Posted March 14, 2015 Share Posted March 14, 2015 I'd have to go with the earth's as well, especially since you haven't got a decent earth strap to the body as it will be creating a false ground reference point. I deal with this in amplifiers all the time as they're especially sensitive to ground loops, eddy currents etc.., to resolve this we star earth everything although that might not be so practical in a car. 1 Quote Link to comment Share on other sites More sharing options...
BlownCorona Posted March 14, 2015 Author Share Posted March 14, 2015 Yep I agree, hopefully that's the issue, no idea where that earth strap ended up in the rebuild! Quote Link to comment Share on other sites More sharing options...
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