UA-65274002-1

Jump to content


Photo
- - - - -

Instrument Cluster Temp Gauge reading cold after obd2 swap


  • Please log in to reply
15 replies to this topic

#1 Dark Ride

Dark Ride

    Senior Member

  • Members
  • PipPipPipPip
  • 1,291 posts

Posted 17 October 2017 - 12:49 AM

I am officially stumped on this. Ever since I did the OBD2 swap on my 90 grand prix I can't get the temp gauge to read properly. Once the car is warmed up, the pcm sees 180f, but the gauge on the instrument panel on shows roughly 130-140. I understand these work by resistance, with decreasing ohms as the sensor gets hotter. i confirmed there is almost no resistance from the sensor to the cluster and cluster to engine block. The sensor is giving roughly 340 ohms at 180, which seems in line but maybe I'm wrong. Please help, it's making me insane because I think the car is running cold.
-Mitch Reed 1998 Grand Prix GTP Supercharged A Few Mods 1990 Turbo Grand Prix Project Car 1995 Chevy Lumina Winter Beater, Complete with no OD mod

#2 White93z34

White93z34

    Grand Potato

  • Administrators
  • 11,444 posts
  • LocationPittsburgh, PA

Posted 17 October 2017 - 12:56 AM

As I recall it uses a different sensor for the gauge then the ECT that the computer uses.


-Chris D.

chrissig.jpg

1992 Chevrolet Lumina Z34 3.4L TDC v6 Getrag 284
1990 Pontiac Turbo Grand Prix 3.1L v6 Hydramatic 4T60 Qty:2
2001 Cadillac Seville STS 4.6L DOHC v8 Hydramatic 4T80
1987 Chevrolet Camaro Z28/IROC-Z 5.0L v8, Hydramatic 700R4
2007 Ford Ranger 2.3 i4 Automatic


#3 Dark Ride

Dark Ride

    Senior Member

  • Members
  • PipPipPipPip
  • 1,291 posts

Posted 17 October 2017 - 01:17 AM

Originally it did, however the 99 harness that's in it now has a single sensor that feeds both.
-Mitch Reed 1998 Grand Prix GTP Supercharged A Few Mods 1990 Turbo Grand Prix Project Car 1995 Chevy Lumina Winter Beater, Complete with no OD mod

#4 Imp558

Imp558

    Proud TransCelestialsexual

  • Contributing Member
  • 3,628 posts
  • LocationErie PA.

Posted 17 October 2017 - 01:33 AM

the circuit for the temp gauge sending unit on a 3-wire sensor uses the case as a ground. I wonder if you have a bunch of sealant or Teflon tape on it or something that is not allowing it to make a ground

Banner.jpg

"If everything seems under control, you're not going fast enough"  - Mario Andretti

 

1996 Regal L67/4T65E-HD swapped - 1995 Buick Regal GS - 1980 Dodge Sno-Commander - 1968 Empi Imp on '67 Pan - 2001 Chevrolet Express 3500


#5 Dark Ride

Dark Ride

    Senior Member

  • Members
  • PipPipPipPip
  • 1,291 posts

Posted 17 October 2017 - 01:57 AM

the circuit for the temp gauge sending unit on a 3-wire sensor uses the case as a ground. I wonder if you have a bunch of sealant or Teflon tape on it or something that is not allowing it to make a ground

That's possible, checking for resistance between the exposed brass on the sensor and the block/housing should confirm that correct?
-Mitch Reed 1998 Grand Prix GTP Supercharged A Few Mods 1990 Turbo Grand Prix Project Car 1995 Chevy Lumina Winter Beater, Complete with no OD mod

#6 Imp558

Imp558

    Proud TransCelestialsexual

  • Contributing Member
  • 3,628 posts
  • LocationErie PA.

Posted 17 October 2017 - 03:42 AM

Yes, also resistance between ground and the single pin on the bottom row willtest the sensor. You can't rule out that the scaling may simply be wrong on that year of sensor for that year of gauge.

Banner.jpg

"If everything seems under control, you're not going fast enough"  - Mario Andretti

 

1996 Regal L67/4T65E-HD swapped - 1995 Buick Regal GS - 1980 Dodge Sno-Commander - 1968 Empi Imp on '67 Pan - 2001 Chevrolet Express 3500


#7 Dark Ride

Dark Ride

    Senior Member

  • Members
  • PipPipPipPip
  • 1,291 posts

Posted 17 October 2017 - 03:51 AM

I'll test the resistances tomorrow and let you know. I'm going to check the shop manuals on the 90 & 99 as well to compare the scaling like you mentioned. I feel like there were close when I initially did this, but maybe not close enough.
-Mitch Reed 1998 Grand Prix GTP Supercharged A Few Mods 1990 Turbo Grand Prix Project Car 1995 Chevy Lumina Winter Beater, Complete with no OD mod

#8 Imp558

Imp558

    Proud TransCelestialsexual

  • Contributing Member
  • 3,628 posts
  • LocationErie PA.

Posted 17 October 2017 - 04:01 AM

If you jump that wire to ground and everything is good from there to the gauge it should jump.

Banner.jpg

"If everything seems under control, you're not going fast enough"  - Mario Andretti

 

1996 Regal L67/4T65E-HD swapped - 1995 Buick Regal GS - 1980 Dodge Sno-Commander - 1968 Empi Imp on '67 Pan - 2001 Chevrolet Express 3500


#9 vipmiller803

vipmiller803

    Advanced Member

  • Contributing Member
  • 304 posts
  • LocationDetroit, MI

Posted 17 October 2017 - 02:00 PM

Perhaps retest at 180 for the 340 ohms, but connect one of your leads to the block instead of the sensor body to rule out the sensor grounding issue. Sometimes testing for resistance can be inaccurate if the absolute value is small (ie engine block to sensor body) due to instrument error.


Edited by vipmiller803, 17 October 2017 - 02:02 PM.

1995 Buick Regal Custom 2DR - 3.8L - DD - 4th Engine, 3rd Transmission, and counting...

2001 Dodge Ram 2500 4x4 - 5.9L Gas

1993 Jeep GC LTD - 4.0L - Snow Days Ride


#10 Dark Ride

Dark Ride

    Senior Member

  • Members
  • PipPipPipPip
  • 1,291 posts

Posted 17 October 2017 - 05:48 PM

Confirmed only 0.1 ohms between sensor body and block. Jumping the wire feeding the gauge caused it to jump to 280 (as expected since there would be no resistance) also confirmed roughly 340 ohms at 180 again. I checked the electrical diagrams and the range between what the cluster expects and what the sender provides is slightly different. The cluster looks for 1400 ohms at 100f and 60 ohms at 280f. The sending unit provides 1365 ohms at 100f and 44 ohms at 280f. If anything it should read higher then right? Thoughts?
-Mitch Reed 1998 Grand Prix GTP Supercharged A Few Mods 1990 Turbo Grand Prix Project Car 1995 Chevy Lumina Winter Beater, Complete with no OD mod

#11 vipmiller803

vipmiller803

    Advanced Member

  • Contributing Member
  • 304 posts
  • LocationDetroit, MI

Posted 17 October 2017 - 08:12 PM

You could try a potentiometer to dial in exactly what resistance the gauge wants to see at the right temp. The CTS is changing resistance but obviously 340 is on the cold side for the gauge. You could place the cts but those are unreturnable once installed.


Edited by vipmiller803, 17 October 2017 - 08:13 PM.

1995 Buick Regal Custom 2DR - 3.8L - DD - 4th Engine, 3rd Transmission, and counting...

2001 Dodge Ram 2500 4x4 - 5.9L Gas

1993 Jeep GC LTD - 4.0L - Snow Days Ride


#12 Dark Ride

Dark Ride

    Senior Member

  • Members
  • PipPipPipPip
  • 1,291 posts

Posted 17 October 2017 - 09:28 PM

I'm beginning to think it must have to be the "curve" of the resistance changes. That the new sensor is more gradual and the old one was steeper after say 130f, so that when it was 180f, resistance was only 150 or something. Either that or I have a lazy gauge...
-Mitch Reed 1998 Grand Prix GTP Supercharged A Few Mods 1990 Turbo Grand Prix Project Car 1995 Chevy Lumina Winter Beater, Complete with no OD mod

#13 Dark Ride

Dark Ride

    Senior Member

  • Members
  • PipPipPipPip
  • 1,291 posts

Posted 17 October 2017 - 11:30 PM

So I had some really old resistors laying around and i confirmed that I need roughly 150 ohms for the gauge to read 180. So... is there a way to reduce the resistance without messing up the lower end? I could wire a resistor in parallel but that would reduce the resistance too much when it's cold.
-Mitch Reed 1998 Grand Prix GTP Supercharged A Few Mods 1990 Turbo Grand Prix Project Car 1995 Chevy Lumina Winter Beater, Complete with no OD mod

#14 Dark Ride

Dark Ride

    Senior Member

  • Members
  • PipPipPipPip
  • 1,291 posts

Posted 22 October 2017 - 01:03 AM

After eliminating everything else, it seems I don't have a choice but to install the old sensor if i want this to read correctly, so that's what I'll end up doing. I'll let you know how it goes, thanks for the suggestions guys.
-Mitch Reed 1998 Grand Prix GTP Supercharged A Few Mods 1990 Turbo Grand Prix Project Car 1995 Chevy Lumina Winter Beater, Complete with no OD mod

#15 vipmiller803

vipmiller803

    Advanced Member

  • Contributing Member
  • 304 posts
  • LocationDetroit, MI

Posted 23 October 2017 - 02:36 PM

Good plan. Are you thinking just plum it in somewhere?


1995 Buick Regal Custom 2DR - 3.8L - DD - 4th Engine, 3rd Transmission, and counting...

2001 Dodge Ram 2500 4x4 - 5.9L Gas

1993 Jeep GC LTD - 4.0L - Snow Days Ride


#16 Dark Ride

Dark Ride

    Senior Member

  • Members
  • PipPipPipPip
  • 1,291 posts

Posted 23 October 2017 - 04:48 PM

Yeah, this is on an L36 so I'm thinking I'll drill and tap right above the stock one. I'm installing my turbo kit so I had it half pulled apart anyway so I popped the thermostat housing off and it looks like the thickness should be sufficient and it won't impend coolant flow or hit the thermostat.
-Mitch Reed 1998 Grand Prix GTP Supercharged A Few Mods 1990 Turbo Grand Prix Project Car 1995 Chevy Lumina Winter Beater, Complete with no OD mod




0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users