coolant temp sensor questions 3500-7730-fiero

[merlot566jka]

can the signal from a cts be shared?

here is the situation, ive put a 3500 into my fiero. the 3500 only has provisions for one coolant temp sensor, i need one for the ecm and one for the guages, can i use the one thats in the head of the 3500 for both the guage and the ecm? or will it half the signal?

if it cannot be shared, where else can i put a cts on the 3500?

[merlot566jka]

and to add, what is the purpose of the hose that goes under the fuel rails, leading from the thermostat housing back into the pump inlet? i didnt need the heater output hose that came from the other side of that, could i eliminate that entire junction and tap where the metal pipe leaves the thermostat housing?

[IsaacHayes]

It's a thermistor so it can't be shared. I've heard there is a coolant drain plug in the back of the block that you can put a single wire temp sender in on the 3400's. Maybe the 3500 is the same? You'd run this one to the gauge. Others have re-threaded a 3wire one to fit in the stock location but you can't turn it down much or far without it cutting through on a lathe. Maybe you could drill a hole in the thermostat housing and thread it and put a 3wire or single wire in there like the 3400's have?

That pipe returns hot coolant to the pump to go right back through the motor. Basically it helps the motor warm up faster. When the thermostat opens, it moves a plunger back and blocks that off, forcing coolant only through the thermostat (radiator) and heater core.

[zofo61]

The set of 3500 heads I have has a blank on the oposite head with an allen head...put it there....same thread as the CTS.

[ForcedFirebird]

The 3400/3.4 RWD hybrids are using the three wire temp sender in the block instead of the two wire. This way you can send signal to the guage and ECM, but I also noted the 3500 heads have a location for a sender. I was going to try to use the iron head sensor there, but haven't checked the threads - guess zofo61 has.

[merlot566jka]

ya threads are the same but there isnt any room inbetween the timing cover and head, plus thats the cold side of the coolant.

this 3 wire cts you speak of, got a part # or a veh i can get one off of?

[ForcedFirebird]

ya threads are the same but there isnt any room inbetween the timing cover and head, plus thats the cold side of the coolant.

this 3 wire cts you speak of, got a part # or a veh i can get one off of?

Three wire sensor GM part number: 10096181

[3100 MPFI]

if you go to a parts store, and they want to know a car that gets the 3 wire sensor, tell them 1996 Pontiac Grand Prix 3100 SFI. That is what I use to get mine.

[merlot566jka]

thanks, ill go to the yard and pick a couple up and give it a whirl....which wire is which?

[IsaacHayes]

Lots of 3100 1996 vehicles will have the 3 wire. L bodies too (beretta, corsica) probably N bodies too etc. I think even the old "4tech" "iron duke" 2.5l used a 3 wire.

Remember though the 3 wire won't fit in the head. So you'll have to stick it somewhere else. Not sure if it will fit in the block anywhere in a drain plug but you can try. If not like I said I've heard the single wire from like a 94-95 beretta/etc fits there. The single wire is in the back of the head.

Not sure on the pins or colors, but if they are these colors then this is what it is: Yellow/black ECM signal, green-gauge signal.

[merlot566jka]

i found a place to tap for the other sensor, on the thermo neck. now i just have to see if the cts used for guages and the ct for the ecm are the same

[3100 MPFI]

The 3 wire sensor goes in the same place as the 2 wire sensor (lower intake manifold. I also have the 3 wire sensor on my 1990 Grand Prix 3.1 MPFI.

As for the wires, the connector is the same as the TPS. There are 3 wires. 2 are side by side, and one is in the middle on top. The middle one on the top is the green wire which is the same wire for the single wire GAUGE sender.

The 2 side by side are the black and yellow, and they go in the same way as the stock connector.

[Superdave]

I would tap the LIM in the same place that the 3400 LIM is, tap it for the 3 wire sensor... This is what i have planned for next year.

I had these problems when i first installed my 3500, the 3500 CTS is the same P/N as the LS1 sensor. I had one in the front head and one in the rear, my temp sensor would always read way high. Caused all kinds of weird problems...

I ended up getting a 3 wire and having it turned down to fit in the head, took 2 tries by the machine shop but the final one worked great.

[IsaacHayes]

To those that went from the temp sender in the head for the gauge to the 3 wire, did it read differently? And if so does it read cooler or hotter than it used to?

[JMo60]

I did the switch when i did engine swap, i dont think it reads any different.. it reads right what my brothers stock '95 3100 cutlass reads