changing coolant temperature sensor

[jhyman]

Hey guys. I have a 96 TA and the fans are not coming on when the temperature goes up. The fans will come on when I turn my AC on so its not the fuse for the fans. I already had that one happen and fixed that problem. Now I think that it is the sensor. Could it be a relay gone bad? The lady at Advanced told me that it was probably the sensor. She said that she probably sells a couple of them a day, and that it is common for my car. So I got the sensor. After all it was only 8 dollars. Now the big problem. The Haynes Repair Manual tells me that it is behind the left manifold, and in between two of the spark plugs. Is there any way that I can change it without taking the manifold off, and how? Also what kind of seelant should I use, and how much coolant should I be prepared for when I take the old one out? Just let me know all the things that I should be watching for please. Thanks guys.

[N20LT4Bird]

You're looking at the sensor for the guage. You want the sensor thats on the water pump, thats for the PCM. The sensor on the side of the block doesnt have anything to do with your fans. You may need to change the temp sensor for the PCM. Best bet is to have it scanned and watch coolant temp to see if its accurate.

The other thing to do is to see if you have power at the relay when the temp comes up. If there is power there, then check the other side of the relay, trace it until you find the culprit. Do you have 2 fans? One is deligated as strictly A/C duty, thats what you may hear kicking on. The first fan motor may be bad. there are many possiblities here. Do some investigation before you change the sensor.

[N20LT4Bird]

P.S. Try to avoid taking advise from parts store guys or gals Theres a lot of guys here who are real good (much better than I) that could help. If you need a step by step, let me know.

[jhyman]

how do I check the relays to see if they are ok?

[BAS]

From Helms Manual, 1995, 6e3-c12-1
low speed fans -
the cooling fans are controlled by the pcm based on inputs from the AC system, engine coolant temperature (ect) sensor and vehicle speed sensor (vss).

the pcm will command low speed fans ON when ect is above 226F. the pcm will tuns the fans OFF when the temp drops about 5F. the minimun ON time for low speed fans is 50 seconds.

HIgh speed fans-
the pcm will command high speed fans ON when any of the following conditions exist at idle.
-certain DTCs set (trouble codes)
-a/c head pressure above 248 psi
-ECT above 235F

If the high speed fans were turned on by the
ECT, the pcm will switch the fans back to low
speed when the temp drops about 5F. Minimun ON time for HI speed fans is 30 seconds.

It appears from the diagrams, that grounding
D2 of cooling fan relay #1 (to turn on fan 1),
and grounding F5 of relay #2 (to turn on fan 2).

grounding each of those should turn the fans on
low speed.
Ground J2 of relay #3 (in addition to relay #1 and #2) should set the fans in high speed mode.

pull the relays out (remember which waay they go), and get an eletrical wire, shove it in there, and ground it some where. (with the ignition on).

That'll test all the relays. the relays are under the hood.

Tell us how it goes.

Originally posted by jhyman
how do I check the relays to see if they are ok?

[N20LT4Bird]

BAS, when you say it kicks on high or low speed FANS, do you mean both? My fan wiring is modified from original, but when it was stock, I remember only 1 fan coming on, unless the A/C was on.

[BAS]

Originally posted by N20LT4Bird
BAS, when you say it kicks on high or low speed FANS, do you mean both? My fan wiring is modified from original, but when it was stock, I remember only 1 fan coming on, unless the A/C was on.

It says in the helm in 95 late production cars
that both fans operate together. I assume this
is the same for 96?

My 94 and early 95 are both high speed fans, with 2 relays.

if you have 2 relays and not 3, then you don't have
the low speed (both), high speed (both) at the same time.

Thats all I know. Your mileage may differ.
They might of changed it back in 96?

[N20LT4Bird]

I could be dillusional too.

[jhyman]

hey where do I shove the wire in at to test my relays?

[BAS]

Originally posted by jhyman
hey where do I shove the wire in at to test my relays?

In the eletrical connector under the hood.

Are they #'ed? You have to remove the relay.

[jhyman]

yes but when you take the relay out there is something like five plugs. Which one of those do I shove the wire in and do I need to put the relay back in while the wire is in it to test it. Just an update: I tested where the relays plug in with a voltmeter, and they tested out fine. The problem is that has nothing to do with the actual relay itself. Also I know that both the fans work because when the AC is on they both come on. So from what I understand that means that it could be one of two problems - Either the relays are bad, or the sensor in the water pump is bad. I am going to get the relays from a parts store and test them that way I think. Are the relays identical, or are all three different in some way. In other words, can I just buy one relay and test each area out with the good relay, or do I have to buy all three? If I figure out how to test with the wire then I will do that instead. Thanks.