I have been having issues with gauges under-reading on my track car, so yesterday, I hooked up the guages direct to the car battery (to eliminate any loom issues), and dropped the senders, wired up also, into a kettle, and boiled it. I have two VDO 52mm temp gauges which were used to do the tests with: 1) 50 - 150 degrees C (for oil) - "150 gauge" - OEM Mk1 GTI 2) 40-120 degrees C (for water) - "120 gauge" - bought new since non VW-supplied Here are my findings - every single sender I have was tested. There's no particular order - I dug them out, tested all. Some are marked identically & are grouped: Part no 150 gauge 120 gauge Sender volt Sender temp Other markings at boil at boil markings markings 049 919 563 A 105 88 24V180ELTH Not stated 05-92 049 919 563 A 107.5 88 24V180ELTH Not stated 05-92 049 919 563 A 102.5 84 6-24V 150 degrees C 11-86 801/16/2 049 919 563 A 105 87.5 6-24V 150 degrees C 3-86 801/16/2 Zip all :-s 100 82.5 12V 125 degrees C none 049 919 501 A 92.5 77.5 12V max 125 degrees C FKO DB 049 919 501 93 79 12V 120 degrees C 11-81 804/6/2 049 919 501 94 77.5 12V 120 degrees C 7 82 804/6/2 027 919 501 98 80.5 12V 120 degrees C 5 93 804/6/6 The only one that worked correctly is highlighted in red. This is now fitted to my oil temp gauge! There is no accurate reading for the 120 guage, with the best being 88 degrees! You can also see small variation between identical senders. The other markings are meaningless to me - dates I assume in column one though, but the others.... electronics gurus? Off the back of this, has anyone any suggestions as to what sender I should be using for my 120 degree guage?
Could it be that the water temp gauge is calibrated to deliberately under-read? People aren't very good at appreciating that engine coolant operates at higher than atmospheric pressure, and so doesn't boil at 100C. Intuitively, having your coolant temperature showing as 100C sounds too hot because of our familiarity with water boiling at this temperature at normal pressure. So they knock 10 or 20 degrees off the displayed temperature to make you feel better. No such perceptual worries about oil temp, because we don't visualise oil boiling? Is there any user-available calibration screw on the back of the gauge, at all?
I spoke to a VDO agent at they confirmed temps are actual temps so there is no offset for water pressure. Apparently the gauges/senders are reasonably accurate, but give or take a little. A 150 degrees sender suits a 150 degrees gauge A 120 degrees sender suits a 120 degrees gauge - all fairly predictable, yet not according to my testing results. I'm going to have the 120 gauge checked next. Some sender resistance data which may be useful to someone one day: Code: [B]40 - 120 degree gauge[/B] Temperature Resistance [COLOR="White"]......[/COLOR] ohms 40 287.4 60 134.0 70 95.2 80 69.0 90 51.2 100 38.5 110 29.4 120 22.7 Code: [B]50 - 150 degree gauge[/B] Temperature Resistance [COLOR="White"]......[/COLOR] ohms 50 322.8 65 173.5 80 122.5 100 62.2 110 48.1 120 36.5 130 29.9 140 23.1 150 18.6
049 919 563 A - oil temperature gauge sender, 1 pin white, 0-180C: MK1/2 Golf MFA oil temp sensor, also used on MK1 type VDO oil temp gauge 049 919 501 A and 027 919 501 are superceeded by 049 919 501 - temperature sender, 1 pin black, 0-125C: coolant temp gauge sender, MK1 Golf, MK2 2/3 Golf 16v 1H0 919 563 - oil temperature sender, 0-150 C: MK3 Golf GTI oil temp sender for MFA 049 919 563 B - oil temperature sender, 1 pin blue, 0-180C Audi VDO gauge temp sensor (not same rating as VW oil temp sender) From the haynes manual, resistance values for 049 919 501 A, 027 919 501 and 049 919 501: 20C - approximately 1000 ohms 60C - approximately 250 ohms 100C - approximately 75 ohms
Great -that makes sense of what's in the first 2 lines of the table in post 1: "24V180ELTH" I'll report back when I've had the 120 gauge tested. At the moment I've got an "049 919 563 A" sensor fitted to the water temp and have "red lined" the gauge at 88 degrees. Kinda rubbish and bodgy really!
Always been interested in how accurate these are, especially since there are so many slightly different senders and gauges around. Not sure if this will make a difference, depending on the cleverness of the electronics inside (probably not very) they may read differently if you have 12v or 14.5v supplying them - might be worth a try while you've got the kettle warm. Probably easiest to hook up a charger - they usually run at 14vish Have you corrected for your altitude too ?