Temperature sending unit questions

[brett25]

hey guys i have a question re: 1987 944 n/a temperature sending unit. I believe that this year has two sensors at the head for determining the engine temperature. I suspected a problem with my temp guage so i went to clean the terminals and see if that helped. the thing is when i got at the sending unit there was only one. the place for the second one just showed threads. the only wires available were two wires that conected to the two terminal posts on the one sending unit. my question is do i need the second sending unit? what happened here? did a PO do something? does the temp sender check coolant temp or the tem of the metal at the head? can i hook up an after market sender to that second post? why are there two sending units anyway and will having only one affect the reading i am getting at the guage?

anyway, sorry for all the questions, but you prolly understand what i am asking.

Thanks for any assistance and happy holidays!!

[todwic]

You should have a sender for the DME and a sender for the gauge. There's another sensor in your AFM.

[brett25]

What is the DME and what is the AFM?
Thanks!

[todwic]

DME = Digital Motor Electronics = the guy that tells your injectors to inject, your spark plugs to spark, and such. AFM = Air Flow Meter = lets your DME know how much air is going in so it knows how much fuel to inject and when your spark should hit.

[turbohead7]

The sending unit is the smaller sensor in the head with one wire going to it. This sending unit is for the guage only, it affects nothing else. The larger sensor with the blue(?) connector is the CTS or coolant temperature sensor. The CTS is responsible for engine temperature signal to the engine computer or DME. This sensor will not affect guage readings. The car should start without it. But I find it hard to believe it's missing as it goes directly into the coolant passage in the front of the head next to the two 6mm hex bolts. I'am thinking the sending unit is missing but then how'd the guage work? Get back to us on this one.

[todwic]

Originally posted by turbohead7
The sending unit is the smaller sensor in the head with one wire going to it. This sending unit is for the guage only, it affects nothing else. The larger sensor with the blue(?) connector is the CTS or coolant temperature sensor. The CTS is responsible for engine temperature signal to the engine computer or DME. This sensor will not affect guage readings. The car should start without it. But I find it hard to believe it's missing as it goes directly into the coolant passage in the front of the head next to the two 6mm hex bolts. I'am thinking the sending unit is missing but then how'd the guage work? Get back to us on this one.

In the post 85/2 cars, the sensor for the gauge has two leads. One for the gauge and one for the idiot light. You're right about it affecting nothing else. You can use the new style gauges with the old engines, you just use the bigger prong. If you use the old style sensor with the newer cars, you won't be able to hook up the light sendor. resistance values remain somewhat the same. close enough for gov. work. The real name for the CTS (and I mention this not for the sake correction for correction's sake, but for the purpose that if he tries to order a CTS he may have some trouble.) is the NTC II.

I also find it hard to believe that either sensor is missing, as they both go into the water jacket.

To help you pinpoint your problem, turbo is right about the NTC II sensor has a blue connection much like the type on your fuel injectors, while your temp sender for your gauge is just the prong type. Yours should have two prongs. if not you have an early style sender.

[brett25]

hey guys, thanks for your replies. Basically I have a sensor which is connected via two wires. One is blue and the other has a yellow stripe on it. they are the push on type terminals. this sensor is closest to the front of the car. aprox. 4 inches down toward the rear of the car is a second "port" which is showing just threads, but looks identical to the "port" that the first sensor is screwed into. there is no leaking of coolant from this second port. when i looked up temperature sending units at pelican, they indicated two of them for this year (87) for $38. so i figured that the other one goes into the other hole in the block. the funny thing is that my temp gauge seems to work fairly well-if anything it may be too high in its readings (thats why i suspected a fault in the sensor). so i dont knoew what the second sensor is for and why i am not getting coolant coming from the hole, or what on earth my beloved PO did to the car. i thought maybe these temp sensors just measured the temp of the aluminum at the head rather than the water in the jacket.

let me know if this information helps at all

ps turbohead, i belive that according to your info i do, in fact, have the coolant temperature sending unit and am missing the gauge sending unit-although as i said, my gauge does seem to work.

[todwic]

I stand corrected. I went out and looked at my block (yeah, I have an extra one laying around) and the NTC II sensor doesn't go into the jacket. It's just a blind hole. You have the gauge sending unit with the blue wire and the striped wire. you are missing your NTC II sensor. This tells the DME the temperature of your engine. As your temp goes up, it leans the fuel mixture because a warm engine doesn't need as much fuel. You should get one.

[SoCal Driver]

There should be two temp sensors in the block under the number one intake runner. One in front of the other.

The early blocks have a blind hole for the single wire temp sender that goes to the temp gauge. The later blocks have a larger tapped hole that does go into the water jacket. A better design.

But both early and later blocks have the temp sensor for the engine electronics --- the DME. This is about three to four inches in front of the temp sender for the gauge. Has the same type connector on it as the injectors.

Take another look. You need the sensor for the DME for the car to run right. You don't need the one for the gauge but it does help for peace of mind. I wonder if you have an early block in your car.

[SoCal Driver]

Hey Todd! Looks like he may have an early block in a later car.

Wierd.

[todwic]

It appears to be so! Here's what I think: Who ever swaped engines in your car used an early block. since the late model sender gauge wouldn't fit into the blind hole where it is supposed to go, he/she put it in the hole that your NTC II sensor goes in.

What I THINK needs to happen (and anyone feel free to correct me if I'm wrong!) is you need to buy a temp sensor for an 83/84 model car, live without a warning light (which is very very small anyway) and put the gauge sender in the hole that doesn't have anything in it and buy a NTC II sensor and put it in the hole that your gauge sending sensor is in now. You now need to find the little blue clip that attaches to you NTC II sensor. it's probably under your intake plenum. Follow the wires that come out of your firewall that lead to your DME.

[todwic]

reason is that the early gauge sender is shorter than the later sender. early only has one prong, late uses two.

[SoCal Driver]

Interesting.

Here are the temp senders.

Early gauge.

Late gauge.




DME

[brett25]

hey guys thanks for the replies. here is what i see: i do have the sensor that looks like an injector in the front, next in line (aprox. 4 inches or so toward the rear of the vehicle) is a sensor with two wires ( the blue and yellow stripped one) a few inches down from that in the same plane (just a few inches toward the rear) is an identical looking hole for something (that is missing) it is a treaded hole not too large and doesnt apear to be leaking any fluids. so, since this year calls for two temperature sensors, i figure thats where the second ought to go. only thing is-whats it for? i have the DME and the gauge covered i believe.

[todwic]

Nope, that's all the sensors that you need. You're good.

[brett25]

ok thanx todwick-i figured maybe that second one is the idiot light? I dont care if i dont have that one as long as my temp guage is working ( im always looking at it anyway )
Brett

[todwic]

naw, idiot light is incorporated into the new sender. It's the smaller of the two prongs.