?Weird temps from gauge?

[smokinshogun]

So all USED to be fine, until I connected the alternator input cable to the case via screwdriver .....so replaced all the battery cables with 2 gauge. Everything was fine for a while meaning the temperature gauge was reading in middle of normal, then it started reading really low like barely getting past bottom line. So figured the pretty new fail safe thermostat went south. Or the 16 lb vented cap was no good. Decided to replace the thermostat and cap since didnt feel much pressure or heat from top radiator hose. Also while the gauge read low the fans still seemed to cycle normally. Both temp sensors had been replaced lately. So driving back from checker I was just turning around in a parking lot and noticed the temp gauge stayed Exactly with the amount of force of right turns. Meaning if I turned a sharp right the gauge would go to the middle then back down when I straightened it out. So installed a aftermarket electric gauge and after getting as many bubbles out as I could took a short drive after I was sure the thermostat opened at 180 and system was pretty pressurized. Meaning the gauge works right? So went around the block and temps went to 230 so I turned on the a/c because no fans were spinning. It cooled it down to 210. So I shut it off and watched it slowly crawl to 190 after 30 minutes.


Soooo heres where I am now? So why did the temp gauge before only read while turning right? Why did the fans not turn on when temp climbed? This all started around the beginning of my story so im at this point its pretty annoying knowing it started because of my mistake.


On an totally related un-related topic If found they knock sensor that I replaced was hissing it seemed? So went to tighten it a little and snap ......so just kinda left the connector empty and snapped peice inside block. How could I solve this one too?

Thanks for the help!!

 

[SHOZ123]

The gauge temp sender is a grounding resistive load device. If the signal is fluctuating then the ground resistance is changing or the gauge itself is FUBARED.

The cooling fan situation runs off the two wire 5V sender that is supplied the 5v by the PCM and the variable ground signal returns back to the PCM. This controls the low speed fan on earlier SHOs and high speed too on later SHOs (>1994 IIRC).

When you turn on the A/C that is the high speed fan and depending on year is the only time it will come on. It may be that either the two wire temp sender is bad or the low speed fan relay in the CCRM is bad or the dropping resistor is bad if the low speed fan is not coming on at ~220F.

 

[smokinshogun]

what could cause the ground resistance to fluxuate to fluxuate? Would it happen to be related to when I ran the battery ground it was kinda short so its routed kinda tightly?

Also tried moving the aftermarket gauge into dash and it started reading 230 at cold. Then started it went to 280+. So all I did was shorten the power wire and the sender wire. Or is something with my gauge wrong.

Well the fans used to turn on right when they were supposed to. And both do come on pretty fast when ac is on max. Both temp sensors were replaced about 2,000 miles ago. The ect with a brass one. Could this possibly be a ground problem? and as the engine flexed it changed the amount of resistance.

 

[SASHO91]

When you turn on the A/C that is the high speed fan and depending on year is the only time it will come on. It may be that either the two wire temp sender is bad or the low speed fan relay in the CCRM is bad or the dropping resistor is bad if the low speed fan is not coming on at ~220F.

could you elaborate on that one Paul. I use my flr. Def. as a fan control(A/C Deleted) is that not the high setting?

 

[SHOZ123]

I guess I should have said any A/C mode, or anything but floor or vent.

 

[SASHO91]

I was refering to the year comment....

 

[SHOZ123]

It appears as if the mtx cars up to '93 only had low speed fan. The '94 mtx as well as all atx V6 SHOs have both a low speed and high speed fan. Some had two fans some had one?

For the +94



Cooling Fan, Electric

The fan control system consists of:

A two-speed radiator electric motor on all 3.0L/3.0L FF, 3.2L SHO and 3.8L engines with ATX.

Two one-speed engine cooling fan motors attached to a fan shroud located behind the radiator on vehicles equipped with 3.0L SHO engines and MTX.

The radiator electric motor is wired to operate only when the ignition switch (11572) is in the RUN position, thereby preventing radiator electric motor operation after the ignition switch is turned to the OFF position.

WARNING:
DISCONNECT THE RADIATOR ELECTRIC MOTOR PRIOR TO PERFORMING ANY UNDERHOOD SERVICE SINCE THE RADIATOR ELECTRIC MOTOR COULD CYCLE IF THE IGNITION SWITCH IS LEFT IN THE ON POSITION EVEN THOUGH THE ENGINE IS NOT RUNNING.

The cooling fan system is controlled during vehicle operation by the Constant Control Relay Module (CCRM) and Powertrain Control Module (PCM) 12A650 which will energize the radiator electric motor under the following conditions:

Radiator electric motor is turned on with reduced current for the 3.0L SHO and on at low speed for 3.0L, 3.2L SHO and 3.8L if:

a. Engine temperature is higher than normal. Radiator electric motor starts running at 102°C (215°F) and stops running at 99°C (210°F).

b. A/C clutch is engaged.

Cooling fan will run at high speed if:

a. Engine temperature is higher than desirable and radiator electric motor has been operating at low speed. Radiator electric motor starts running at high speed at 110°C (230°F) and stops running at 107°C (224°F).

On 3.2L SHO engines, low speed radiator electric motor operation is achieved by using a dropping resistor in series with the motors.

The 3.0L/3.0L FF, 3.0L SHO and 3.8L use a dual winding radiator electric motor in which low speed fan control is achieved through the low fan control winding circuit (no dropping resistor).

The normal operation and cycling of the radiator electric motor causes the temperature gauge indicator to read between the mid-point and upper portion of the temperature gauge scale.

The slightly higher indicator reading returns to mid-point when radiator electric motor operation begins.

=<93
Cooling Fan

The fan control system consists of a two-speed fan on all 3.0L, 3.2L SHO and 3.8L engines with ATX or a one-speed fan on 3.0L SHO engines with an MTX, attached to a fan shroud located behind the radiator. The cooling fan is wired to operate only when the ignition switch is in the RUN position, thereby preventing cooling fan operation after the ignition switch is turned to the OFF position.

WARNING:
DISCONNECT THE COOLING FAN PRIOR TO PERFORMING ANY UNDERHOOD SERVICE SINCE THE FAN COULD CYCLE IF THE IGNITION SWITCH IS LEFT IN THE ON POSITION EVEN THOUGH THE ENGINE IS NOT RUNNING.

The cooling fan is controlled during vehicle operation by the Constant Control Relay Module (CCRM) 12B577 and Powertrain Control Module (PCM) 12A650 which will energize the cooling fan under the following conditions:

Cooling fan is turned on for the 3.0L SHO and on at low speed for 3.0L, 3.2L SHO and 3.8L if:

a. Engine temperature is higher than normal. (Fan starts running at 102°C (215°F) and stops running at 99°C (210°F).

b. A/C is on and vehicle speed does not provide enough natural airflow. (Fan starts running at speeds at or below 69 km/h (43 mph) and stops running at 77 km/h (48 mph).

On 3.0L and 3.2L SHO engines with ATX, low speed cooling fan motor operation is achieved by using a dropping resistor in series with the motor/motors.

The 3.8L uses a dual winding fan motor in which low speed motor operation is achieved through the low speed motor winding circuit (no dropping resistor).

Normal operation and cycling of the engine cooling fan will cause the temperature gauge indicator to read between the mid-point and upper portion of the temperature gauge scale. The slightly higher indicator reading will return to mid-point when fan operation begins.