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I needed to replace my coolant temp sensor in my 84 Z28 305 HO. The one on the left is what came out of the car, but the one on the right is what the parts store and websites said I needed. I can't find one like the one I pulled out. Any suggestions?
That is not a sensor. It is a sending unit for the Temp gauge.
The "sen-sore" is for the ECM. The sending unit with the OEM connector is no longer made. The replacement works just fine, you just may have to put a female spade connector on the wire...
I screwed the sensor in, plugged it into the existing connector as it was already like a spade and fit pretty well. However, the gauge is staying bottomed out (not moving above 100) and the fan is not coming on. The fan came on fine before I overheated. When I use a IR thermometer it says the heater core hoses are around 200-210, and the radiator hoses are around 180-190
How can I check to see if the gauge is bad vs the wiring to the sending unit, etc? Could it be as simple as a fuse somewhere?
The gauge sensor has nothing whatsoever to do with the fan. All it does is work the gauge.
"Gauge is staying bottomed out" means, essentially, not connected. However, that said, there IS one other explanation... the sending unit for an idiot light is open (not connected) when it's in the "happy" range, and closes (shorts the connector pin to ground) when in "alarm". Sounds kinda like that's what you have.
Simple test is, stick a piece of wire such as an OBD1 code reader https://www.staples.com/staples-jumb...product_525949 in the connector on the wire, and short it to ground. The gauge should peg. If so, the wiring and gauge are good, and your new SU is the wrong one.
No it's not a fuse. Mere logic would tell you that: ONE fuse works ALL the gauges, so if ANY gauges work, the fuse is OK. It's even simpler than that.
Your IR temp readings sound completely fine to me. On the cool side if anything.
You could see the sending unit I purchased in the pictures above. It doesn't look at all like what came out of the car. But others told me that this should work. After this post, when I started the car, the gauge goes all the way hot, then all the way cold (showing that the gauge works, as I've read).
I will try the obd1 suggestion you made.
So what decides when to turn the fan on and off? And how would I check that?
That doesn't sound like a place I will be able to easily access, is it?
Is there a way to test before crawling under the car and trying to find that thing?
That doesn't sound like a place I will be able to easily access, is it?
Is there a way to test before crawling under the car and trying to find that thing?
Not really. If you can get your hand in there to disconnect the wire, grounding that should turn on the cooling fan.
If the fan does not come on, you have another problem...
It's the same hole in the head casting that the gauge SU is in, just, the other head. Not really that much of a problem to get to.
The wire going to it is green w white stripe, single-pin round Weatherpak connector, coming from a harness at the top of the engine. There's another thing nearby with the same style of connector, the knock sensor; but that's down at the bottom of the block, about an inch above the oil pan. Don't confuse the 2.
So here is where I am at:
I removed the fan, put jumper wires on it and touched the battery. The fan did not run. So I ordered a new fan from E-bay that came in today, so we later tonight we will see if that works
I used alligator clips to ground the green wire that goes to the coolant temp sending unit, and the gauge topped out, indicating that the gauge and the wiring are working. I just have to get a working coolant temp sending unit.
I also replaced the alternator, and the new one (which looks identical to the old one) is rubbing on the bracket. So I'm taking the bench grinder and grinding off a little bit of the metal of the bracket to make clearance for the alternator. I have no idea why this was not a problem before.
Sorry im having the same problem and want to confirm. So my gauge does not move when i ground it out from the green wire on driver side sensor to the negative battery. I do have 11.5 v going to the gauge cluster as i tested it by removing the gauge and the prongs on the right was where my 12 volts were at. the top and left side prongs had .005 volts. I also did a OHM out on many different variations on the gauge and was 83.1 OHMS from top to left, 110 OHMS from left to bottom, 62 from bottom to right, left to right is 49 ohms. I read i should have a OL reading. So my guess is my gauge is bad.
My question is since the gauge did not move when i ground it out is my gauge bad?
My understanding (and my experience) was grounding made the gauge go all the way up. If the gauge doesn't move, the gauge is bad. If you order from most places, I believe you should be able to return the gauge if it turns out the problem is deeper in the cluster. But you certainly need to double check first.
Even though mine works, I still don't think it works great. When driving at highway speeds, the temp stays around 140-150. When idling, the temp goes up to over 210, and only then does the fan come on. I think the thermostat is a185, and I thought the fan came on at 195, but could be wrong. I feel comfortable ignoring the temp at this point since I've seen it work correctly several times.
