Electrical Gremlin Help!!!!!

[Bigsho2]

Ok, so here we go, I have looked through the forums as much as a week permits and so I'm asking for some advice on a couple of issues. the car is a 1991 SHO with automatic temp control first and for many of you the easiest I have an air bag light that flashes 4 over and over and over, my research shows this to be safing sensor, which I'm guessing is the rear airbag sensor located on the firewall some clarification/affirmation here would be very helpful. The second issue is a little more perplexing, when I bought the car it had a brand new ATC control unit (dash controls) installed (could be bad), the car was blowing at full speed only no matter the setting, turning it off would then change it to blow full speed from the defroster. 2 days after ownership everything went to normal and everything worked correctly. But then it would periodically make quick bursts of high speed notably each time I would touch the brakes, use the turn signals, headlights turned on or I accelerate hard. This lasts for just seconds and it then returns to the requested speeds. I believe this could be a headlight switch or dimmer switch if not a wire. (reading tonight is saw something regarding vacuum lines?) the braking /acceleration leads me here. and lastly the coolant light comes on occasionally, the car was 1/2 quart low when purchased topped off correctly and then days later the light came on although it had not previously came on when it was low. I shut off the car to check it and it was good and restarting it the light went out and stayed out. until this afternoon it came back on and went out on its own. I predict a possible grounding issue if anyone has a list of grounds to check I would be happy to clean them up I am not an electrical engineer, but am comfortable with circuits. Lastly if you are still reading this thank-you, I vow to research until I pass out several days straight before bothering anyone with my issues.

 

[Bryan]

The airbag sensors are in the bumper. Good luck finding them as I believe are discontinued. You can try a junk yard for another Taurus's sensors. They are all the same pretty much. I disconnected mine on my 90 SHO. As for the coolant light? It's the overflow bottle. In my 92 SHO (same motor as the 90), the little sensor thing is like a long stick that goes down into that bottle. Age and the coolant just ruins it. Do as I did and unplug the sensor and the light goes out forever!

 

[rubydist]

the fan blowing only at full speed is usually the blower speed control module being bad or sick.

the air only coming from the defroster is a vacuum issue to the auto temp control unit - somewhere a vacuum line has likely cracked or broken. that line runs from under the hood through the firewall to the control unit.

the coolant sensor can be disconnected as Bryan suggests, but I prefer to clean all the crud off the bottom of the sensing unit, which generally makes it work properly again.

 

[sperold]

The flashing air bag light is very common on the Gen 1 cars.
The "safer sensor" is located in the foot well area on the drivers side, behind the parking brake apparatus. And I have never seen it, just heard about it.

Generally speaking, shine up the sensor attachment fasteners that you can find, like the rad support, and the other front ones are at the tip of the fenders at the front and are hard to find. I think they are behind the marker lights and they have a connector that you can find under the hood. That is where they are on a 90 SHO, so be aware that the 91 could be different.

I have found that the code flashing does not always identify the fault, which makes matters much worse.
I have also found that experimenting with your start up procedure can turn off the light. One time, it was leave the key on until the solid light goes off, then start. Other times the light shuts off after about one hour of operation, for whatever reason.

This topic has been well presented on this forum. Here is one of my posts highlighting one of my ordeals

https://shoforum.com/index.php?posts/1444687/

I have another post that gave all the part numbers for the sensors. I found you can buy them new if you have the part numbers, on E-Bay, but they were around $50.00 each, so I did not exercise that option.

Only get parts for your airbag system from a 91. The 90 is different; and the 92 to 95 seem similar to each other but are different from your 91.
Any 91 Taurus model has your parts, it doenot have to be a SHO.

 

[Bryan]

the fan blowing only at full speed is usually the blower speed control module being bad or sick.

the air only coming from the defroster is a vacuum issue to the auto temp control unit - somewhere a vacuum line has likely cracked or broken. that line runs from under the hood through the firewall to the control unit.

the coolant sensor can be disconnected as Bryan suggests, but I prefer to clean all the crud off the bottom of the sensing unit, which generally makes it work properly again.

I was going to try that on my 92, but the stick separated from the sensor completely and now just lays in the bottom of the bottle. And honestly... It's just an idiot light. I was considering putting the digital display back in so that low coolant light needs to go anyway.

 

[sperold]

If you don't want to fiddle around and glue the apparatus back together, then it is better to disconnect the electrical connector. For some reason the idiot light does mess up other functions, and I cannot begin to explain why. It is the only thing that does not make any sense.

 

[Bryan]

If you don't want to fiddle around and glue the apparatus back together, then it is better to disconnect the electrical connector. For some reason the idiot light does mess up other functions, and I cannot begin to explain why. It is the only thing that does not make any sense.

It's a Taurus man. Everything makes sense. And by that I mean it makes no sense. But to make sense of it you need to be senseless. Heck my 92 is a totally different beast after the deer decided to pay the drivers side of the car some attention and "redesign" most of it.

 

[Bigsho2]

What a great bunch! Thank you all for the advice and for the link to chase things down. I have not had time to fiddle with the Gremlins yet and I will keep you posted as to what I find. This weeks project is a full front end rebuild on the car. If anyone else has any suggestions feel free to chime in. I will be pulling all bag sensors and modules to clean up grounds and apply dielectric grease this weekend also I found the positive battery terminal was broken causing a poor connection and that could be causing a lot of issues. I will be cleaning up the coolant level sensor as well. I’ll save the a/c for last provided the batt terminal doesn’t fix it. I attached a pic of the car. Needs some TLC but we are working on it.

 

[luigisho]

Bad battery and/or alternator can cause all kinds of problems and make you chase your tail.

 

[zoomlater]

Nice car.

 

[Bigsho2]

Yea I’m embarrassed I hadn’t seen it before. It was under the factory rubber cover and as it had not given any issues starting or charging I hadn’t had reason to look plus the battery was new when I got it. I noticed it when disabling the SRS system. Thank you zoomlater, I bought it for my daughter paid 1000.00 bucks for it. We feel very fortunate. Needs some paintwork on the roof, decklid, and grill as well as some front seat repairs. But otherwise it’s in great condition. He even had the timing belt serviced 4K miles ago.

 

[Bryan]

Pfft... A/C. I prefer the 455 A/C. Four windows down at 55 mph. Saves me a lot of hassles of fixing the aging A/C parts. Also make sure that sunroof isn't leaking. Those things are water and rust magnets.

 

[Bigsho2]

Ok I have waited a week to see how things go, I replaced the positive terminal, ensured the negative was tight, and cleaned up the body ground. Magically all three issues have gone away. Now I know this seemed simple, but again the car is new to me and still has never failed to start, show any form of charging issues, or battery corrosion this was just not an area of concern. In all the lesson was go back to basics no matter how simple it may sound. I will keep you all posted should the issues arise once again. Thank you all for your responses.

 

[Bigsho2]

Well darn my luck, it’s been back on for a week now. I just don’t get it, this weekend I unplugged the headlight switch, dimmer, auto headlight switch, and the ATC unit all at the same time. And yet still the blower puffs out shortly high speed and the air bag light blinks code 4 every time I touch the brakes or turn signals, or hazards I tested the battery and got 12.63v, tested the cables and pulled .2 millivolts on both the positive battery terminal to the positive terminal on the alternator, and .2mv from the negative batt term to the chassis ground .00mv to the engine. So cables are testing good. What gives?

 

[rubydist]

12.63 V with the engine on or off?

 

[Bigsho2]

This was engine off. Driving today the bag light was lit for the first few hours and now this afternoon it’s off again. I tried shaking wires around under dash when I was in there trying to find a short and the light stayed lit.

 

[rubydist]

4 = Safing Sensor - Diagnostic Circuit Open or Low Primary Crash Sensor Resistance

I would start by replacing the front crash sensor which is approximately at the center top of the radiator, mounted to the top radiator support.

 

[Bigsho2]

I will consult the manual to test and or replace the front center sensor, and this is the safing sensor? I was told that it was behind the drivers kick panel, initially I thought it was the sensor on the firewall. And the manual does not specify which sensor is officially the “safing” sensor.

 

[rubydist]

the one I refer to is the primary crash sensor. that code could mean that the primary crash sensor has too low of resistance, or that the safing sensor is bad. you are correct that the safing sensor is in the driver's kick panel. note that this sensor will be the same from any Taurus or Sable of the same vintage that has abs (which only the high trim levels had).

 

[Bigsho2]

Thank you for the clarification. Everyone’s assistance is greatly appreciated.