AIR temperature sensor Mercury 260 HP

[A164]

Hi Mates,

I have been studying the AIR temperature sensor that is available today. And new one seams to be a bit off compared to the data available from the original.

The original part number is 13221A1.
The currently available sensor is 13221T01

I have put the figures in to excel and made curves for comparison.
The blue line is the original sensor curve. 13221A1
The purple line is the currently available sensor 13221T01
The yellow line is the modified line with a 100.000 Ohm resistance connected parallel to the currently available sensor 13221T01.

The thing is, when starting the engine on the cold days here in pre-spring where the Air temperature is 6-7 °C then it seams to be getting too rich. And when looking at the Ohm line for the current sensor then it makes sense if ECU is acting according to the original.
Just want to share my observation, and wondering if any of you has experience similar to this?
And if you have made any modification to the sensor to improve its curve.

				100000	Ohm
Ohm	Temp °C	Temp °F	Ohm meassured	Modified
3300	50	122,0	2000	1961
3440	49	120,2	2000	1961
3580	48	118,4	2000	1961
3720	47	116,6	2000	1961
3860	46	114,8	2000	1961
4000	45	113,0	2000	1961
4160	44	111,2	2000	1961
4320	43	109,4	2000	1961
4480	42	107,6	2000	1961
4640	41	105,8	2000	1961
4800	40	104,0	5150	4898
4960	39	102,2	5175	4920
5120	38	100,4	5200	4943
5280	37	98,6	5400	5123
5440	36	96,8	5500	5213
5600	35	95,0	5750	5437
5800	34	93,2	5950	5616
6000	33	91,4	6200	5838
6200	32	89,6	6450	6059
6400	31	87,8	6700	6279
6600	30	86,0	7000	6542
6780	29	84,2	7100	6629
6960	28	82,4	7450	6933
7140	27	80,6	7700	7149
7320	26	78,8	8080	7476
7500	25	77,0	8440	7783
7750	24	75,2	8640	7953
8000	23	73,4	8970	8232
8250	22	71,6	9300	8509
8500	21	69,8	9500	8676
8750	20	68,0	9800	8925
9070	19	66,2	10050	9132
9390	18	64,4	10425	9441
9710	17	62,6	10900	9829
10030	16	60,8	11400	10233
10350	15	59,0	11850	10595
10720	14	57,2	12250	10913
11090	13	55,4	12700	11269
11460	12	53,6	13000	11504
11830	11	51,8	13650	12011
12200	10	50,0	14300	12511
12600	9	48,2	15000	13043
13000	8	46,4	15500	13420
13400	7	44,6	16200	13941
13800	6	42,8	17200	14676
14200	5	41,0	17900	15182
	4	39,2
	3	37,4
	2	35,6
	1	33,8
	0	32,0

[A164]

I did this small video to illustrate my point,,,,.

https://www.youtube.com/watch?v=wJ5r...ature=youtu.be

[sdriche]

Did you every get a response on this? I'm trying to diagnose a similar issue. At 37 degrees F my sensor is reading 31k OHMs which seems way too high. At 65 degrees F I'm getting 14k OHMs which is close to the temp and reading you are getting on the new sensor in your video. I can't figure out if I have a bad sensor or not.

[A164]

Hi, No you are actually the first to comment this,
At 65°F it should meassure around 9350 OHM, and if you are getting 14000 OHM the sensor is telling your ecu that temperature is around 41°F which then result in giving more fuel.
If you want to be sure take the sensor out and you need at thermometer and a cup of water. And messure the reading when dipping the sensor tip into the water and holding the thermometer close to the sensor tip then take the readings.
And i would say if your current sensor is way off. At 65°F it should be around 10300 OHM. (10.3 KOhm) for a new sensor.
The first collum of OHM´s is data found for original sensor. Second collum of OHM´s is data found for new current awailable sensor.

I preferr to modify my one a bit and currently I actually need to hold the chocke function in the key some 5 seconds when started to keep it running when starting cold.

[sdriche]

What did you use to lower the resistance? I assume you wired a resistor in parallel ? I, trying to reduce my resistance by about 4K ohms. Thanks,

[A164]

Hi Sdriche,
4K Ohm will change your output too much. I used a 100K Ohm in parallel which will lower a rasitor at 7500Ohm to around 6000Ohm.
You can play with the values on this link.
https://www.allaboutcircuits.com/too...ce-calculator/

[H2Okie]

You could try using an appropriately rated potentiometer in place of a fixed resistor allowing you to vary the resistance at different engine temperatures for testing . I made up a low cost test set up for for air temp sensors using a 1/2 " thick piece of aluminum plate with holes drilled for the tip shape of the sensor and a 1/8" hole to accept the the temp probe for a digital cooking (meat )thermometer . I simply use a shop drop light with a 60 watt incandescent bulb to heat up the plate . This set up allows you to slowly heat up the sensor and record the temp / resistance reading and plot a curve on log paper much more accurately than dipping probe in a cup of water .

[sdriche]

i ordered a new sensor. I'll let you know if my readings are different than yours when I get it. Thanks for the help.

[sdriche]

New sensor reads 3k ohms lower than the old one. This is the new part number 13221T01.

I'm still reading about 1k higher than what the chart states so my new sensor is consistent with what you are experiencing. I may add the resistor as well to bring it down a bit but out of the box side by side with the old one (in the same air) I get a 3k lower reading. I've been running rich and never knew it.

[A164]

Hi Sdriche,
I have a Brucatto ACU where i can adjust different fuel parameters, and I newer felt that I could get it adjusted down in fuel when ideling. So therefore I now run with a 75000ohm resistor in parallel to the original. Which gives theese theoretical readings, a pracrical test would be good to do to verify this.

Ohm	Temp °C	Temp °F	Ohm meassured	Modified	75000 Ohm
4800	40	104,0	5150	4819
4960	39	102,2	5175	4841
5120	38	100,4	5200	4863
5280	37	98,6	5400	5037
5440	36	96,8	5500	5124
5600	35	95,0	5750	5341
5800	34	93,2	5950	5513
6000	33	91,4	6200	5727
6200	32	89,6	6450	5939
6400	31	87,8	6700	6151
6600	30	86,0	7000	6402
6780	29	84,2	7100	6486
6960	28	82,4	7450	6777
7140	27	80,6	7700	6983
7320	26	78,8	8080	7294
7500	25	77,0	8440	7586
7750	24	75,2	8640	7747
8000	23	73,4	8970	8012
8250	22	71,6	9300	8274
8500	21	69,8	9500	8432
8750	20	68,0	9800	8667
9070	19	66,2	10050	8862
9390	18	64,4	10425	9153
9710	17	62,6	10900	9517
10030	16	60,8	11400	9896
10350	15	59,0	11850	10233
10720	14	57,2	12250	10530
11090	13	55,4	12700	10861
11460	12	53,6	13000	11080
11830	11	51,8	13650	11548
12200	10	50,0	14300	12010
12600	9	48,2	15000	12500
13000	8	46,4	15500	12845
13400	7	44,6	16200	13322
13800	6	42,8	17200	13991
14200	5	41,0	17900	14451

Compare to first and last collum which need to be close to get it close to the original reading.

But I now need to keep pushing the choke which is in my key some seconds after motor starts.