Coolant Temp Sensor ?
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From: Vancouver WA
Coolant Temp Sensor ?
Since I've brought the car back on the road, the temp readout displays "low coolant" all the time. The primary fan doesn't come on but the aux fan does. I've been watching the oil temp which use to closely match the coolant and is reading no more than 210 F.
Today I checked almost everything...
1. the fan turns on when the ADL is grounded, so the fan works.
2. the fan switch on the passenger side head is brand new.
3. checked the relay switch by the brk booster, checks out good.
4. fuse is good
Looking through the Haynes manual I passed by something called the Coolant Temperature Sensor which is located at the front lower end of the intake manifold. So now I'm wondering if this could be the culprit or what. Any advice before I blow another brain cell would help?
OOPs the readout is "Low Temp" not "LOw Coolant". Sorry all, I read a post about low coolant and I guess it stuck in my head.
[Modified by 87Beast, 9:22 AM 8/1/2002]
[Modified by 87Beast, 9:28 AM 8/1/2002]
Today I checked almost everything...
1. the fan turns on when the ADL is grounded, so the fan works.
2. the fan switch on the passenger side head is brand new.
3. checked the relay switch by the brk booster, checks out good.
4. fuse is good
Looking through the Haynes manual I passed by something called the Coolant Temperature Sensor which is located at the front lower end of the intake manifold. So now I'm wondering if this could be the culprit or what. Any advice before I blow another brain cell would help?
OOPs the readout is "Low Temp" not "LOw Coolant". Sorry all, I read a post about low coolant and I guess it stuck in my head.
[Modified by 87Beast, 9:22 AM 8/1/2002]
[Modified by 87Beast, 9:28 AM 8/1/2002]
Team Owner
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2. the fan switch on the passenger side head is brand new.
You can see in that picture where the sensors (there are 2) screw into the intake manifold. They are in the accel one on the right.
Le Mans Master
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From: And on the fifth day, subpoenas were served to Obama senior staff
Re: (87Beast)
Drivers side head is the temp switch for the aux fan. Passenger side head is the sensor for the digi-dash temp guage. Temp sensor for ecm (which controls your main fan) is below the TB where Scorp shows in his pic.
I would suggest that you first make sure all the air is out of the system if you are getting a low coolant light (sensor in radaitor about half way down below cap on passenger side).
Usually loss of the ecm coolant temp sensor would cause driveability problems as well, but it's cheap and easy enough to replace.
Pete
I would suggest that you first make sure all the air is out of the system if you are getting a low coolant light (sensor in radaitor about half way down below cap on passenger side).
Usually loss of the ecm coolant temp sensor would cause driveability problems as well, but it's cheap and easy enough to replace.
Pete
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Re: Coolant Temp Sensor ? (87Beast)
The ECM turns on the main fan from temp info from the sensor under the TB. If your temp gauge always reads lo, then the connection to the sensor on the right side of the engine is open, or the sensor is defective. If you ground the green/white wire on the relay it should close and the fan come on. Also, if you turn on your a/c , the fan should come on.
Burning Brakes
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Re: (trupp)
Once you get the fans to come on right, you'll probably have the coolant light coming on even if the radiator and bottle is full.
I have had 3-C4's and all had the same problem. If you get into the cooling system in any way like draining the system or even installing a new fan switch (in the left head on my '87) an air bubble develops in the system and keeps the low coolant light coming on. In the case of my '84 and '85 (no low coolant light) it just overheated all the time. And doesn't go away until you do this.
You have to jack up the front of the car (one side is enough) so the radiator is higher than the engine. Take the radiator cap off and let it sit overnight. In the morning the air bubble has worked it's way out and you can top off the system and no more probs.
BIG JIM
I have had 3-C4's and all had the same problem. If you get into the cooling system in any way like draining the system or even installing a new fan switch (in the left head on my '87) an air bubble develops in the system and keeps the low coolant light coming on. In the case of my '84 and '85 (no low coolant light) it just overheated all the time. And doesn't go away until you do this.
You have to jack up the front of the car (one side is enough) so the radiator is higher than the engine. Take the radiator cap off and let it sit overnight. In the morning the air bubble has worked it's way out and you can top off the system and no more probs.
BIG JIM
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Re: Coolant Temp Sensor ? (hotwilzz)
My readout is displaying "low temp" not "low coolant" (reason is at the modified post at top".
So now it looks to be either the CTS or the pass. side sensor (which I just bought from Schucks 3 weeks ago). With this narrowed down I'll test both of them and see if anything happens.
So now it looks to be either the CTS or the pass. side sensor (which I just bought from Schucks 3 weeks ago). With this narrowed down I'll test both of them and see if anything happens.
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Re: Coolant Temp Sensor ? (87Beast)
Hey Beast, bring your ride out to end of River Road on Saturdays about 5 or so, lots of different hi-po machines and vette guys get together too. We'll help ya out if ya can't resolve it or if ya just want to meet the guys. :yesnod:
Le Mans Master
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From: And on the fifth day, subpoenas were served to Obama senior staff
Re: Coolant Temp Sensor ? (87Beast)
If you installed a temp "switch" in the passenger head, it would cause the digi-dash to read "low temp". You need a temp sensor in that position.
Still does not explain why the main fan does not turn on as they are not related.
I understand about the 85 cars now, but believe that the 87 is the same setup as my 89:
Passenger head above starter: Temp display sensor for digi-dash
Drivers head between #1 and #3: Temp switch for aux fan
Intake manifold below TB: ECM coolant temp sensor.
I also believe the sensors for the digi-dash and ecm are identical, but not sure. Two wire units.
The coolant temp switch for the aux fan relay is a single wire unit that simply grounds the relay above a certain temp.
Still does not explain why the main fan does not turn on as they are not related.
I understand about the 85 cars now, but believe that the 87 is the same setup as my 89:
Passenger head above starter: Temp display sensor for digi-dash
Drivers head between #1 and #3: Temp switch for aux fan
Intake manifold below TB: ECM coolant temp sensor.
I also believe the sensors for the digi-dash and ecm are identical, but not sure. Two wire units.
The coolant temp switch for the aux fan relay is a single wire unit that simply grounds the relay above a certain temp.
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From: Vancouver WA
Re: Coolant Temp Sensor ? (PeteL)
Mark84_L383 are these gatherings every Saturday? if so I'll try to make it there. And is the river road at the end of 4th Plain by the lake?
BT
PeteL, actually it could be a temp sensor, at least this is what the guy at the part store gave me. It has a blade type conn. I'm hoping that this isn't a broken pos.
[Modified by 87Beast, 10:04 AM 8/1/2002]
BT
PeteL, actually it could be a temp sensor, at least this is what the guy at the part store gave me. It has a blade type conn. I'm hoping that this isn't a broken pos.
[Modified by 87Beast, 10:04 AM 8/1/2002]
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Re: Coolant Temp Sensor ? (Mark84_L383)
got it thanks.
If anyone who has a shop manual could you let me know what the voltage and the resistance of the CTS is? I just tested it out at 2.3 V and resistance is not displaying. This could be the problem
If anyone who has a shop manual could you let me know what the voltage and the resistance of the CTS is? I just tested it out at 2.3 V and resistance is not displaying. This could be the problem
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From: And on the fifth day, subpoenas were served to Obama senior staff
Re: Coolant Temp Sensor ? (87Beast)
Remove wire.
Sensor resistance is dependant upon temperature:
210* = 185 ohms
160* = 450 ohms
100* = 1,800 ohms
70* = 3,400 ohms
40* = 7,500 ohms
20* = 13,500 ohms
This across the two pins on the sensor.
Sensor lead should provide +5V (to ground) and a return to the ecm. You can't measure anything on the return really.
[Modified by PeteL, 8:44 PM 8/1/2002]
Sensor resistance is dependant upon temperature:
210* = 185 ohms
160* = 450 ohms
100* = 1,800 ohms
70* = 3,400 ohms
40* = 7,500 ohms
20* = 13,500 ohms
This across the two pins on the sensor.
Sensor lead should provide +5V (to ground) and a return to the ecm. You can't measure anything on the return really.
[Modified by PeteL, 8:44 PM 8/1/2002]
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Re: Coolant Temp Sensor ? (PeteL)
Thanks
I'm using the diagnosis kit from mid america which plugs directly into the sensor and the connection and has a split that goes to the voltometer. When I tested this, I had the car on but not the engine running. I'll try and run it for a few minutes and take another reading.
Also I did a volt test to the conn. wire to both left and right side sensors and the one on the left side is @12 V the right side is @9.3 V. is it normal for this voltage drop?
I'm using the diagnosis kit from mid america which plugs directly into the sensor and the connection and has a split that goes to the voltometer. When I tested this, I had the car on but not the engine running. I'll try and run it for a few minutes and take another reading.
Also I did a volt test to the conn. wire to both left and right side sensors and the one on the left side is @12 V the right side is @9.3 V. is it normal for this voltage drop?
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Re: Coolant Temp Sensor ? (PeteL)
I also believe the sensors for the digi-dash and ecm are identical, but not sure. Two wire units.
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From: And on the fifth day, subpoenas were served to Obama senior staff
Re: Coolant Temp Sensor ? (87Beast)
I don't see much use for that adapter.
Use your ohm meter directly on the sensor. Do not try and read resistance with the adapter, it means nothing as you are looking back into the ecm power source and reference transistor.
5V is the supply voltage and ground, that is what you should read on an open connector. At operating temp of 200* you should find 1.5 to 2.0 volts on your MAD adapter.
The switch in the drivers side head simply grounds the relay, what you read with a volt meter will depend upon the internal resistance of your meter, the coil resistance of the relay and and internal resistance of the switch. This effects nothing but your aux fan, it is not connected to any other circuit.
Use your ohm meter directly on the sensor. Do not try and read resistance with the adapter, it means nothing as you are looking back into the ecm power source and reference transistor.
5V is the supply voltage and ground, that is what you should read on an open connector. At operating temp of 200* you should find 1.5 to 2.0 volts on your MAD adapter.
The switch in the drivers side head simply grounds the relay, what you read with a volt meter will depend upon the internal resistance of your meter, the coil resistance of the relay and and internal resistance of the switch. This effects nothing but your aux fan, it is not connected to any other circuit.
Le Mans Master
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From: And on the fifth day, subpoenas were served to Obama senior staff
Re: Coolant Temp Sensor ? (Ray Quayle)
Thanks Ray. Now I understand how folks get the switch and the dash sensor mixed up. Think the oil temp sensor is a single as well (and just had it apart 3 months ago). This is what happens when you get old!
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Re: Coolant Temp Sensor ? (PeteL)
After finding a code 14, 33, and 36(????) I went out and replaced the CST. As of now I'm not setting off any codes, BUT the temp gauge still displays "Low Temp". Unless there's a way to check if the temp sensor ( by teh passenger side heads) is good or bad, I'll replace it tomorrow.
By the by, the code 33 was set off because I forgot to reconnect the MAF - silly me :crazy:
And I don't know what the 36 is for?
By the by, the code 33 was set off because I forgot to reconnect the MAF - silly me :crazy:
And I don't know what the 36 is for?