HELP PLEASE, 02 GTS fan not opperating

[dave6666]

My 97 GTS is doing the exact same thing. I added coolant to the system and let it idle in the garage. I had the heater on and everything was fine. It never got over the third mark. I then turned the a/c on to see if that would make it get hotter. It got about 5 degrees warmer, and I turned the a/c off to see if it would cool back down. When I turned the a/c off the fans quit running. I swapped the relays for the starter and the high speed fan. Nothing changed. I assumed the relay on the left back was the high speed, and swapped it with the starter on the back right. I did not check the front left, and the front right is open.

Contrary to some saying that with the AC on the car runs cooler (because the fan is forced on), my car does not. That is because the AC condenser is 150 to 175 F (checked with an IR) so it preheats the 90 to 100 deg ambient air to something hotter.

If your car is running at the third center mark it may not be hot enough to run the fan without the AC.

 

[Rock Morgan]

When I turned the a/c off the temp guage moved between the third mark and 250. I then turned the a/c back on and the fans came back on and it cooled down to the third mark. I know relays can test good when they are actually bad. I was told by a mechanic a bad relay can still support a load, just not the full load they are designed for causing them to heat up and fail. Do you think I should buy new relays just to be sure? This did not start happening until the car had run about 20 mins. idling in the garage and the heat had built up.

 

[dave6666]

From my '01 manual...

Same outputs from PCM for normal fan operation.

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[Rock Morgan]

I'll check the on/off relay. I have not checked it and now that I think of it the fan comes on when I turn the key on.

 

[dave6666]

A couple of things for you guys troubleshooting these fan problems.

COMMON ITEMS BETWEEN AC FAN MODE AND NORMAL FAN MODE:

Fuses, Relays, PCM outputs, wiring from relays to fan. All of that can be seen on the manual pic above.

NON COMMON ITEMS:

PCM inputs. The input to the PCM from the AC system and the thermostat for engine cooling control are not the same. The thermostat for engine cooling actually has 3 circuits in it; one for the idiot light in your message center, one for the gauge, and then the input to the PCM for engine management including fan control. Then of course the wiring to these different inputs is not common to each other.





Point of that is, if the fan comes on with the AC but not when the engine gets hot, it does not seem to make sense to look at the common items. If the relays were bad, why would the fan come on when the AC tells it to? But not when the PCM says the engine is hot and needs cooling?

I would get a hold of a Powertrain Diagnostics Manual on the year car you have for further troubleshooting info.

 

[Rock Morgan]

Well, I've checked everything I can check and still no fans. I made an appointment with the doctor (Viper tech) on Friday morning. I'll let you know what he finds.

 

[bumblebee]

When I turned the a/c off the temp guage moved between the third mark and 250. I then turned the a/c back on and the fans came back on and it cooled down to the third mark. I know relays can test good when they are actually bad. I was told by a mechanic a bad relay can still support a load, just not the full load they are designed for causing them to heat up and fail. Do you think I should buy new relays just to be sure? This did not start happening until the car had run about 20 mins. idling in the garage and the heat had built up.

thats exactly what my car does....the fans worked fine..then hour later I tried 20-30 min. on a 85 degree muggy day trying to get my car out of driveway and thats when the fan quite working and not worked since. i swapped the relays around but no luck

 

[bumblebee]

I'll check the on/off relay. I have not checked it and now that I think of it the fan comes on when I turn the key on.

my fan does not come on with key on...only if i turn ac on or disconnect plug from temp gauge sensor sending unit

 

[bumblebee]

Well, I've checked everything I can check and still no fans. I made an appointment with the doctor (Viper tech) on Friday morning. I'll let you know what he finds.

sweeet! because i garrenty its the same problem as mine!

 

[bumblebee]

From my '01 manual...

Same outputs from PCM for normal fan operation.

You must be registered for see images

thanks for the help

 

[Sweet Ride]

Hey all:

Pull the relay box apart and check the wiring that goes to the relays. From time to time the wiring gets hot and burns up. You could have intermittent wiring issues that could cause the problem.

I had this same issue for while and it turned out to be a broken wire in my Roe fan control kit (my fault). My car was always running hot but once I fixed the wire the problem was solved.

You could also have a bad fan motor. Check the wiring connector from the harness to the fan module as well.

You could always resort to the infamous "wiggle test." Turn the car on and start wiggling any and all wires that run to the fan module. This a quick/easy way to check for wiring shorts and has saved me tons of time diagnosing problems over the years.

 

[dave6666]

my fan does not come on with key on...only if i turn ac on or disconnect plug from temp gauge sensor sending unit

Um. Key on does not turn the fan on unless the coolant sending unit tells the PCM that the coolant is hot. I think it's like 210 degrees or so. Are you expecting the fan to come on every time you turn the key to on, regardless of engine temp?

 

[Rock Morgan]

With the a/c on the fan comes on as soon as I start the car, but it only operates on the low speed. This whole thing makes my head hurt. I'll let everyone know what I find out Friday.

 

[dave6666]

With the a/c on the fan comes on as soon as I start the car, but it only operates on the low speed.

That is operating correctly then.

 

[bumblebee]

With the a/c on the fan comes on as soon as I start the car, but it only operates on the low speed. This whole thing makes my head hurt. I'll let everyone know what I find out Friday.

cannot wait until you get yours checked out!

 

[bumblebee]

By the time your gauge gets to that last mark before "the end...," your fan should come on. Mine comes on between the last of the 3 center marks and the 220/225 mark. Whatever that damn mark is. Shuts off about halfway between center marks 2 and 3. I'd let it go smidgen higher just to check things. Once it fully crests that last mark before d-day then yes shut it down and have a floor fan ready to give the beast comfort.

took car out today and maybe the sending unit was bad...I'm getting avout the same readings as you..sweet

 

[Rock Morgan]

Problem found. The Temperature guage is 30 degrees off, everything else is working fine. The temp guage was registering 230-235 when the actual coolant temperature was 202. They told me they have seen this happen on several Dodge vehicles. They are checking to see if there is anything they can do to recalibrate the guage now.

 

[dave6666]

They are checking to see if there is anything they can do to recalibrate the guage now.

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[Rock Morgan]

That's exactly right. They gave me the diagnostic read out and said the guages cannot be recalibrated. Just know that the guage is 30 degrees cooler than it's reading.

 

[Sweet Ride]

That's exactly right. They gave me the diagnostic read out and said the guages cannot be recalibrated. Just know that the guage is 30 degrees cooler than it's reading.

You could always ditch the stock gauge for a Mechanical Autometer gauge...

 

[dave6666]

You could always ditch the stock gauge for a Mechanical Autometer gauge...

Someone inquired about that a while back - pulling the stock gauges and installing better ones in the factory location. Is that possible?

 

[Sweet Ride]

Someone inquired about that a while back - pulling the stock gauges and installing better ones in the factory location. Is that possible?

I don't see why not. I know I have seen pics of a car on this site with aftermarket gauges. I would imagine if you stick with electric gauges it's a pretty easy swap. Going to mechanical (real) gauges would require some work as far as keeping the factory sending units in place. You would have to run a T-block from the head in order to keep the factory coolant sensor in place for PCM input and have the mechanical gauge sensor in place as well. I would imagine this could be done with Oil PSI as well. I did this on a car (non-Viper) that I previously owned and didn't have any issues.

The main problem would be from a looks standpoint as the aftermarket gauges won't have that cool night effect that the stock gauges do. I have considered doing this as the stock coolant gauge leaves alot to be desired from an accuracy standpoint.