temp gauge reads low

[David Anderson]

My VDO temp gauge which is oringinal to the coach reads 20 degrees low.  At normal operating temps it reads 160 when the engine room gauge is 180.  My t-stats are 180, so the engine gauge is correct.  I really like the gauge because it has the Eagle silouette on it which looks cool.  Maybe at one time the sender was changed and it is not correct.   What could I do to fix this?  What info is needed to find the correct parts?

David
1985 Houston Metro Eagle 10
6V92

[Sojourner]

By pass a hot wire from battery to gage's positive stud...if it improve...need to improve the dash's power source.

If not improve...grounded the gage's ground or sender stud It should read to the high limit. If it not...replace gage (be sure it the same voltage as your bus)

If it does...check all for corroded connection from gage to sender unit.

Or replace the sender unit and be sure it installed as per OEM location to receive the proper temperature tap.

FWIW

Sojourn for Christ, Gerald

[WEC4104]

Is the gauge in the engine room the same style as the one in the dash? If so, you could swap them and see if the problem follows the gauge, or stays with the location.

[Len Silva]

Disconnect the gauge from the sender and measure the resistance from the sender to ground. 

Find your gauge on the chart below.  If it's the gauge I think it is at 180 degrees the resistance should be 62 ohms.

Use the attached chart for trouble shooting all VDO gauges.  You can check the resistance of the sender and/or substitute a known resistance to test the gauge.

[luvrbus]

David,look for a resistance loop on the wiring I don't know the location for sure on a Metro 10 but most are on the left corner by the manual gauge or on the back of the gauge find it unroll a couples of loop and see if that will bring it up if not call our good friends Norris or Dan and get a new sending unit   good luck

[David Anderson]

Len,
The chart may not be applicable since this is a 1985 gauge.   According to this site:

http://www.egauges.com/vdo_send.asp?Sender=ATM_94_Temp

Only 2 senders are available.  I cannot remember if I replaced the sender back during the conversion process.  I wasn't keeping good maintenance records in the beginning and replaced a lot of little odds and ends parts.  If I did I may have bought whatever the NAPA guy had to thread into the hole.  There are no markings on the sender. 

The engine room gauge is mechanical, so no swap.  The engine room gauge matches temps shot from a temp gun at the sender block, so I assume it is correct. 

I redid the grounds to the dash a couple of years ago to eliminate some quirky needle readings.  It shouldn't be there.  However, I've never looked at the 12v+ side.   There might be something there.

David

[Sojourner]

David...yes, electric water gage need a good voltage source to read correctly along with good negative wiring/connection to the sender.

Phone me if you will, I can walk you through the step by step quickly.

Eight-six-three-six-three-three-eight-nine-seven-nine.

FWIW

Sojourn for Christ, Gerald

[Len Silva]

It appears that you may have the wrong sender.  I would go with the VDO brand rather than generic.

Try this:  Connect a 100 ohm resistor from the sender terminal on the gauge to ground and check the gauge reading.  Use the chart to figure exactly what sender you need.

Also, just in case you were not aware, don't use any kind of thread sealant on the sender.

Len

[David Anderson]

Got her fixed.  Went to a hot rod shop and bought a VDO323-419 sender.  Installed in the block and she is reading like she should.  It is amazing how I just kind of put up with the low reading all these years.  It's kind of like the cob webs hanging from the chandelier over the dining table.  You know they are there, but you never do anything about it.  Thanks for all your help.

Merry Christmas.
David

[JohnEd]

David,

I think BoboftheNorth's recent experience has sent a lot of us out to verify the performance of our safety equipment.  Remember now, his temp gauge WAS WORKING FINE when it read OVERTEMP.  So who has ever been looking at the temp gauge when it started to spike?  Oil pressure either.  Those gauges are good for assessing the performance and spotting a problem on the horizon but the shutdown stuff was put there at considerable expense by DD and you know how they are.

John