ongoing temp gauge headache
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
That's what he said he did so now what does he (or I) do next. So far as I understand at this point, new gauge is working, sender may or may not be working but if it is working it's not compatible with the resistor on the back of the new gauge. I hate to sound like a broken record and helpless but....what next. I am going to talk to my mechanic monday with all of my new found knowledge.
Find out if in fact he changed the resistor that goes on the back of the gauge.
Find out which sender he put in the car.
Find out if he added anything into the green wire circuit.
Depending on what he says I would recommend putting the original resistor back on the gauge.
Install your new little tester in the green wire and confirm a reading of aprox 210 on the gauge.
If the gauge reads 210 , buy a BWD WT203 sender from Advanced Auto or Orileys , bring that sender home and test it in boiling water to confirm that it reads aprox 80 ohms while boiling. (not confirming will only add to the confusion)
If the WT203 does read 80 while boiling install and test,you should be good.
(hopefully you can get a good reading sender and wont have to resort to altering the back of gauge resistor.If you continue to have problems I'm sure Ernie can find and match a sender to your gauge for you.(pretty sure he offers that service) I would offer to do it for you but I wont be back home for 2-3 weeks.)
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,851
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
That's what he said he did so now what does he (or I) do next. So far as I understand at this point, new gauge is working, sender may or may not be working but if it is working it's not compatible with the resistor on the back of the new gauge. I hate to sound like a broken record and helpless but....what next. I am going to talk to my mechanic monday with all of my new found knowledge.
I think you should follow Rogers advice as far as going back to him. Knowing for sure will help figure out the issue.
If you find the wt203 to read 80 ohms boiling, (and I hope you do) then with the original resistor the gauge should read correctly.
If you install a known good sender knowing that it will go to 80 ohms boiling.. and the gauge fails to read correctly then pull an ohm reading on the resistor. I'm going to verify this, but I believe the original value should be 90-91 ohms.
I stock the WT203 and show it being tested in our prior test in 2009. Roger the lowest value we could get out of one was 95 ohms. We show testing three coming in at 95-105-103. This is not to say that they have not changed something since we did this either. This was over two years ago. Today I just sent two more out to the shop to re-test. I'm kind of excited to see what I get!
Ernie
Thread Starter
Instructor
Joined: Feb 2008
Posts: 211
Likes: 2
You could be right,it might be inline on the green wire. But from sharks OP I gathered that "changing" the resistor "not adding" meant the mech was at the gauge.
Sharks quote from OP:
[ Replaced the sending unit which he said didn't match temp gauge. Changed the resistor 'cause he said wasn't measuring the engine temp correctly.]
Ernie,as you know (but others might not) adding ANY resistor in the green wire can ONLY make the gauge read COLDER,never hotter.
Going from past experience this mech was fighting what we all fight and that is senders that already read TOO cold.
Sharks quote from OP:
[ Replaced the sending unit which he said didn't match temp gauge. Changed the resistor 'cause he said wasn't measuring the engine temp correctly.]
Ernie,as you know (but others might not) adding ANY resistor in the green wire can ONLY make the gauge read COLDER,never hotter.
Going from past experience this mech was fighting what we all fight and that is senders that already read TOO cold.
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
Got your PM Matt,lets see if we can get you on track. You have 2 things going on.
You need to get this corrected ,with the tester in place your dash unit should have read around 210. The dash gauge needs the resistor across the back of the gauge changed. (as I remember you did confirm the resistor change was made at the gauge and not in the green wire input)I would recommend the mechanic put the original resistor back on the gauge. Then retest with the little tester. Hopefully you will end up with aprox 210.
As Noonie says if your engine is running 160 with a 180 thermostat the 180 thermostat is NO good. A good 180 will keep your engine above 180.
I would work on the gauge first,this 160/180 thing is not effecting the gauge accuracy.
OK so the gauge situation is still not resolved. The mechanic checked the entire engine with his laser temp gun and found that it never gets above 160#. Thought it might be his gun so he installed a mechanical gauge set up in place of the factory set up. I have been driving the car around and the mechanical gauge never gets above 160#. I have a small block with a big block De Witts radiator and a stock fan, 180# thermostat. My mechanic has never seen a vette run as cool as mine. He thinks he might block off a portion of the radiator with something to see if it has an effect. Info only the new temp gauge literature sais it is of better quality than the stock and does not need any resistors. Any thoughts?
I would work on the gauge first,this 160/180 thing is not effecting the gauge accuracy.
Last edited by ...Roger...; May 30, 2011 at 05:39 PM.
Thread Starter
Instructor
Joined: Feb 2008
Posts: 211
Likes: 2
Got your PM Matt,lets see if we can get you on track. You have 2 things going on.
You need to get this corrected ,with the tester in place your dash unit should have read around 210. The dash gauge needs the resistor across the back of the gauge changed. (as I remember you did confirm the resistor change was made at the gauge and not in the green wire input)I would recommend the mechanic put the original resistor back on the gauge. Then retest with the little tester. Hopefully you will end up with aprox 210.
As Noonie says if your engine is running 160 with a 180 thermostat the 180 thermostat is NO good. A good 180 will keep your engine above 180.
I would work on the gauge first,this 160/180 thing is not effecting the gauge accuracy.
You need to get this corrected ,with the tester in place your dash unit should have read around 210. The dash gauge needs the resistor across the back of the gauge changed. (as I remember you did confirm the resistor change was made at the gauge and not in the green wire input)I would recommend the mechanic put the original resistor back on the gauge. Then retest with the little tester. Hopefully you will end up with aprox 210.
As Noonie says if your engine is running 160 with a 180 thermostat the 180 thermostat is NO good. A good 180 will keep your engine above 180.
I would work on the gauge first,this 160/180 thing is not effecting the gauge accuracy.
Burning Brakes
Joined: Jul 2009
Posts: 935
Likes: 20
From: Indianapolis Indiana
I seem to have the opposite problem of everyone else.
I have a 69 427 that worked fine when I got it than out of the blue, it started showing a lower reading.
I have done the prior tests.
When I remove the connector- It pegs to the left (even it it was reading before)
If I ground the wire on the engine block, I get max reading.
I just put in a new temp sending unit (GP Sorensen WT203Z TSU5)
It appears to give me a higher reading at around 160 where before I was getting 130.
Any suggestions for when you get a low reading?
thanks
I have a 69 427 that worked fine when I got it than out of the blue, it started showing a lower reading.
I have done the prior tests.
When I remove the connector- It pegs to the left (even it it was reading before)
If I ground the wire on the engine block, I get max reading.
I just put in a new temp sending unit (GP Sorensen WT203Z TSU5)
It appears to give me a higher reading at around 160 where before I was getting 130.
Any suggestions for when you get a low reading?
thanks
