temp. gauge problem

[roper]

Hey guys its been a long time since my last visit. I'm having a little trouble with my temp gauge and need some help. I noticed that my car seemed to be running hot. I changed the thermostat and still running up against the red mark, the car really didnt seem hot though, so I put a thermomater in the radiator and it read 190 so I dont think I am really overheating. anyway, long and short of it I bought a new gauge from ricks camaro's and started trying to put it in. It fits in alright but on the old one there is a little resistor looking board that wasn't supplied with the new one and the bakelite board that the connector plugs plug into are slightly different and the contactor prongs wont fit on it right for the plug. What do I need to do? When I hooked it up and turned on the key it goes all the way over to the cold side and wont move even when the car is at running temp. I then tried to hook the old one up and it now does the same stinkin thing. I must be hooking it up wrong so could one of you guys help me out and describe how it is supposed to be hooked up? I would greatly apprieciate it. its a 69 with console gauges. Thanks in advance. Steve

[rich69rs]

Gage reading constantly at the C or cold (pegged hard to the left) is an indication of high resistance (open circuit).  Low resistance causes the gage to move right toward hot (H).  As temp sending unit senses increasing temp, its internal resistance decreases which causes the temp gage to move from left (C) to right (H).

Attached pic is a schematic of the connections on the back of a 68/69 console gage package.  Bakelite/resistor "boards" as originally supplied should be there.

Next two posts have the general instructions for installing gages in a non gage car.  These may help you trouble shoot your issue.  I apologize for the poor resolution, but I had to reduce it to that level in order to post them.  Enlarge them and although blurry, I think they will still be readable.

Good luck

Richard

[rich69rs]

Page 1 of installation instructions.

[rich69rs]

Page 2 of installation instructions.

[roper]

Richard, Thanks for the pictcure that is exactley how I'm connecting my gauge. So If it is pegging out on the cold side its working, I just need to give it more time to heat up to operating temp. I do have the thermostat out so that may make a difference, Now on the posts that are verticle there is a small square board that looks like some sort of resistance board and had a cardboard insulating washer behind it on the top post only, is this correct?  Will it need to be on the new one also? The bakelite board that ricks camaros sent looks more like the one in the picture that goes to the fuel gauge, it lines up the connectors straight across from each other. I appologise for posting in two spots but wasnt sure where this post should be. Thanks for your input I am going to print out the instructions you sent and put them with my paperwork on the 69. Steve

[roper]

Rich, I ment to say they line up across from each other like the amp gauge, not the fuel sorry. If the car is at operating temp and I plug the guage in, will it take a while then to heat up and register the correct temp? Steve

[tom]

Steve, Just a thought, if you have removed the thermostat, it is possible but not likely that the motor is not getting enough heat to register on the gauge. The temp is meant to be read at or near operating temp and above. since we are not in summer it is possible your motor is not getting over say 150 degrees and therefore may not be hot enough to register on your gauge. Do you have access to an infrared? You may want to find out just how hot you are running.

Tom

[roper]

Yeah you may be right, I'm going to reconnect everything and drive it around awhile and see what happens, I will let you know.  Steve

[rich69rs]

I believe the wound resistor on the bakelite board on the back of the temp gage is for "calibration" purposes and, at least for the original gages, needs to be there.

[roper]

Ok, I must have something wrong here. I drove the car around town today for around an hour or so and the guage will not move from full cold. as soon as the key is turned on it goes to left as far as it can up against the stop. it stayed there for I know an hour while I drove around. I will have to pull it back out. heres the way its connected. The top and bottom have the square wound resistor board on them with one cardboard washer under the top lug. the bottom doesnt have one on it. On the two to the right and left is the bakelite board with the two connections on them. Im quite sure that the plug that goes on it is upside down from the way I took it off but when connected the other way as soon as the key is turned on it goes to full hot all the way against the stop in that direction. What gives? I dont have much hair left to pull out! Steve

[sdkar]

For starters...did you get an OER gauge or Classic Headquarters brand?  This does make a difference as you do NOT use an external resistor with the OER but if you got a Classic Headquarters brand you do have to use an external resistor.  Check out Rick's latest catalog on page 114 for instructions on both brands.

[roper]

sdkar, you are correct. I did in fact buy the classic headquarters brand and when I installed it with the resistor board it seems to be working fine, I thank you all for your help and comments. where I intionally messed up was hooking it up outside of the housing, which in fact was the ground, duh, it would peg all the way hot. Soooooo, me gets to thinkin that I hooked up the plug backwards and I switch them around, anyways......it works now, Thank You.  Steve

[GaryL]

I have a related question if I may.  When I turn my headlights on my factory temp gauge goes higher. What could cause that?  Lower voltage? Regulator not keeping up?

[rich69rs]

Perhaps something to do with the temp gage ground?  See attachment in second post in this string.

The external wire references the temp gage to ground.  The actual circuit through the temp gage goes to ground through the gage, through the sending unit which is grounded by being screwed into the cylinder head.  If those two grounds aren't the same, could be part of the problem.  Possibly turning on the headlights brings everything to a common ground, at a little lower resistance value, which causes your temp gage to read slightly higher.

Just speculation without checking.

[JohnZ]

I have a related question if I may.  When I turn my headlights on my factory temp gauge goes higher. What could cause that?  Lower voltage? Regulator not keeping up?

The temp gauge circuit is calibrated based on a steady 12V reference supply; if other vehicle loads draw down the reference voltage (like idling with the headlights on), it will affect the gauge reading.