I am looking for an oil temp gauge on eBay, and notice some are described as mechanical and others as electrical. Exactly what are the differences between these two types? Don't they all use electrical sender?
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Difference between mechanical and electrical oil temp gauge?
- Thread starter sifan
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sifan
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Please ignore this question. I have found out the differences.
A mechanical guage has permanantly attached sender (bulb) and line. The bulb and line conatain liquid, with the vast amount of liquid being in the bulb.
As the temperature increases, the fluid is evaporated (boiled) raising the presure in the gauge until it reacees the vapor pressure for that temperature.
The readout in you car is actually a mechanical pressure gauge marked in units of presure.
As the temperature increases, the fluid is evaporated (boiled) raising the presure in the gauge until it reacees the vapor pressure for that temperature.
The readout in you car is actually a mechanical pressure gauge marked in units of presure.
sifan
Thread starter
Does this mean the electrical gauge is more reliable then its mechancial counterpart?
If either type of senders becomes bad, does this mean the whole gauge replacement?
If either type of senders becomes bad, does this mean the whole gauge replacement?
Electrical, the snder can be replaced.quote:
Originally posted by sifan:
Does this mean the electrical gauge is more reliable then its mechancial counterpart?
If either type of senders becomes bad, does this mean the whole gauge replacement?
The mechanical gauge/tube/sender is one unit. It would cost more to replace the sender (if you can find an instrument shop to do it) than it would to buy a whole new gauge with sender. Another drawback to mechanical is that you need a hole in your firewall big enough to put the sender through. That is the biggest drawback to a mechanical gauge.
The biggest advantage to a mechanical gauge is thet you can get them with a needle that goes through a 250 to 270 degree turn instead of just a 90 degree turn like the vast majority of aftermarket electrical gauges. You can read them a lot more accurately.
For the same price, mechanical gauges also tend to be more accurate and more durable. The installation can be real PITA though.
I like electrical gauges but my experience has shown me that they often are not near as accurate as the mechanical ones.
The electrical type has two sources of error, the sender and the gauge itself.
Much easier to route through a firewall, and there are less risks of leakage developing with the electronic type, though.
Either can be accurate or not.
Just like a digital tire gauge - it may read to the 1/100 of a lb - whoopee - but it may be off in calibration.
Much easier to route through a firewall, and there are less risks of leakage developing with the electronic type, though.
Either can be accurate or not.
Just like a digital tire gauge - it may read to the 1/100 of a lb - whoopee - but it may be off in calibration.
sifan
Thread starter
The mechanical type sounds harder to install. But, how inaccurate is the electrical type?
Does Autometer make good electrical gauges? Any suggestions on other makers?
Does Autometer make good electrical gauges? Any suggestions on other makers?
No comment on Autometer, I haven't kept up with gauges lately.quote:
Originally posted by sifan:
The mechanical type sounds harder to install. But, how inaccurate is the electrical type?
Does Autometer make good electrical gauges? Any suggestions on other makers?
My semi-educated guess is that any guage that isn't a bottom of the line product will be accurate enoutgh for general pupose use. If a temperature gauge is off 5F degressa at 200F, it doesn't really matter as long as it is consistant, and most gauges are consistant.
I just pulled the 5F out of a smelly place, I don't know if that's the size error you can expect or not.
the problem with electrical gauges is that they are referenced to system power (i.e. nominal 12V). so if your system voltage varies (and it does) so will your gauge reading. a good example of this is to watch your factory gauges and flick your headlights on and off, on my '88 this will cause the oil pressure and water temp (both electrical gauges) to move.
nah... sit in any 88-92 chevy/GMC fullsize pickup and try it, they all do it. the autometer electrical trans gauge in the same truck doesn't.
The gauge should have a regulator built in [like a car's dash gauges].
The Mfrs. know about the vicissitudes of car voltages.
The Mfrs. know about the vicissitudes of car voltages.
Mechanical gauges are more accurate and more expensive. So for the average motorist on the BITOG forum, I think the electrical version is the way to go. Much cheaper and easier to install and the accuracy is sufficient. Pro racers use the mech versions. One trick is to 'tee in' to a existing sensor-say the stock oil pressure sensor location. Now you have the stock oil press warning light still functional and a new elec. oil temp gauge. If you have a auto trans ( heat build up is critical, esp when towing), you can install a trans oil temp gauge in the trans side inspection port and have matching engine oil and trans temp gauges. See egauges.com for some excellent buys on the popular gauges.
Mechanical guages may be more accurate (in some cases), but their accurracy is far too dependent on perfect conditions. They are more suscepible to damage, harder to dampen, etc and when any of this happens, you no longer have a more accurate guage.
in reality they are just for indication and reference, not for actual measurement. what I mean is they will tell you that your tempeture is high or low or there is a 15* difference in old oil and new oil. They aren't really very good at telling you that your actual oil temp is accurately 215*F. the guage would cost alot more than what autometer charges for it to be calibrated and accurate.
It costs approximately nothing to put the sender in boiling water and get an accurate calibration at 212F, or some lower but well known temperature if you are at a significant altitude.quote:
Originally posted by tom slick:
in reality they are just for indication and reference, not for actual measurement. what I mean is they will tell you that your tempeture is high or low or there is a 15* difference in old oil and new oil. They aren't really very good at telling you that your actual oil temp is accurately 215*F. the guage would cost alot more than what autometer charges for it to be calibrated and accurate.
That's funny, I was just looking at some gauges over at www.egauges.com: http://egauges.com/vdo_mult.asp?Type=Outside_Temp&Series=Cyber_Red&Cart=
I think I will be getting an outside temperature gauge for my Subaru - it's nice to know when it's below freezing.
I was looking at the Cyberdyne digital gauges since it's easier to read an LED display in the DIN slot next to the gear shift than a needle...
I may also add a trans temp & oil pressure gauge next summer.
I think I will be getting an outside temperature gauge for my Subaru - it's nice to know when it's below freezing.
I was looking at the Cyberdyne digital gauges since it's easier to read an LED display in the DIN slot next to the gear shift than a needle...
I may also add a trans temp & oil pressure gauge next summer.
Kestas
Staff member
I once had a mechanical gauge (original equipment) on the dash of my 66 Corvette. It plumbed oil directly to the dash. One day the line broke at the gauge, spilling dirty oil on my feet!
oh, yeah, and add to my list "safety issues"quote:
Originally posted by Kestas:
I once had a mechanical gauge (original equipment) on the dash of my 66 Corvette. It plumbed oil directly to the dash. One day the line broke at the gauge, spilling dirty oil on my feet!
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