Hi,

I have a 95 z28. Pretty much stock. The fans won't come on. I am wanting to trouble shoot on my own. What is the quick and easy way for me to by-pass the coolant fan relay to see if the relay is the problem or if it may be something else.

What guage wire is suitable. Will I need to run a ground wire as well...simple questions but I want to make sure I am doing it right.

Do I simply pull out the specified relay, run a wire from the positive terminal on the battery to one of the points which the relay was plugged into, and a ground as well...and if so which points do I use to plug the wire from the + terminal into...

Thanks.

 

http://web.camaross.com/forums/showt...t=hotwire+fans

 

i can tell you now...it's the ECT or engine coolant temp.

look on the water pump for a wire, in the front, driver's side. pull the wire off. if the fans come on, replace that sensor...it's 20 bucks. if the fans do not come on, replace all 3 relays for fan control. if you still have a problem, look into wiring...and finally replace or re-flash the PCM.

 

sorry....to answer the original question. i'd use either a 12 or 10g wire with a spade terminal. look at the relays, they're all going to be facing the same direction except one. take the lead from that one and go DIRECTLY across all the way to the opposite connection. that will take direct power from bat to the source.

 

Hi,

I disconnected the ECT plug. Both fans came on as well as the "check engine light". I drove the car to work (about 20 minutes) and the temperature guage ran up to the same zone it had before the ECT plug was pulled and the fans weren't coming on...

I was thinking that if the fans were on all the time for the 20 minute ride to work it would keep the engine cool. However this didn't happen...was I wrong to think this...will everything work fine once the ECT is changed?

Thank you,

Peter

 

I would look into finding out if your gauge is wrong. Plug the sensor on the water pump back in and monitor engine temp through the PCM with a scanner. Compare that to the dash gauge. Perhaps the fans are not coming on because they don't really need to (engine actually not getting hot).
You also need to state just where the needle is getting to on the gauge when you thing it is hot.

 

Hi Shoebox,

The guage is in celsius so it reaches 115c (or approx 225F) and the fans still are not coming on. I don't have a scanner( I have a 95 z28 with the OBDII but with the OBDI connector...I believe that is what I remember the last time I went to buy a scanner...but did not know which brand...price doesn't really matter as I will be keeping this car indefinitely and want a good one...any suggestions on type?)

Is my reasoning that with the fans runnning all the time for that 20 minute ride that the engine shouldn't have been running at 225F...I could tell as the engine was sucking for power as well when it is that high.

Thank you,

Peter

 

115c is closer to 239f than 225f, stock the fans dont turn on till the temp hits 225f so that wouldn't be abnormal, however 239f is a problem by that temperature both fans should be on.

For a scanner i'd prolly get a cable from akmcables.com and either buy datamaster or download freescan.

 

The PCM sensor and the temp gauge might not read exactly the same. They could be several or more degrees different. So, if your gauge reads ~225° and the PCM sees it a little lower, the fans won't come on. You may be chasing a problem that does not exist.

Anyone that works on modern cars has to have a scanner. Autoxray, Actron and others make scanners with the right cable that will work on your car (OBD-I with OBD-II shaped connector). A cable, PC and software, as already mentioned, are options, too.

 

Sorry I forgot to mention a critical point. I replaced the stock thermostat 3 years ago for a 160F (?) one....the one that comes on at a lower temp than the stock one...

 

A lower temp thermostat, alone, will not keep the engine cooler when there is no air flow across the radiator (like stopped or sitting in traffic).

 

Hi Shoebox,

Removing the ECT and the fans coming on...would this mean the ECT needs replacing such as Severous01 mentioned? It made sense until the engine still went greater than 225F even with the fans running. This temperature problem only started in the last two weeks...

Also I value your opinion and I am wondering what scanner you use?

Thanks.

Peter

 

Unplugging the sensor does not prove anything about the sensor. If you unplugged a good sensor, the same thing would happen. You can test the sensor and it's wiring with info from my Tech Page.
I use TTS Datamaster for OBD-I on my computer and also have a hand held older AutoXray scanner that does OBD-I and II.

 

i told you how to test it. if you remove it and put it in hot water, measured with any cooking thermometer, you can set the temp up and match to specified temps. 225*f should read around 100 or so ohms. room temps should yield thousands of ohms...around 6 or 8k

 

Ok.

Here is what I know so far (without a scanner):
1. The relays all work when I place them individually in the fog light relay spot.
2. I checked the ohms for the temp indicator sensor. The DVM read 232ohms when the temp guage read approx. 90c on the dash.
3. I checked the ohms for the water pump sensor. The DVM read 246ohms when the temp guage on the dash read approx. 90c.
4. The harness of the temperature indicator sensor read 11.86 volts which is normal (12Volts).
5. The harness of the water pump sensor read 5 volts which is also normal.
6. I jumpered relay #2 from F4 to F1 and the RH fan came on at high.
7. I jumpered relay #1 from D4 to D1 and the LH fan came on at low.
8. I disconnected the C100 harness connection and grounded the H connector (dark blue wire from C100 cavity) AND NOTHING HAPPENED...the fan or fans never came on.
9. Then I grounded the J prong on the other side of the C100 harness (closer to the fans) AND NOTHING HAPPENED...as well the H prong grounded never turned the fans on.

SO...what should we consider now?