1999 V6 Cooling fan issues.

Any help would be appreciated. I searched previous post but no clear answer.

Fans are not coming on with or without A/C on, gauge sitting at or higher then the mid point on gauge. I can jump them at the relays and get them to come on but in normal mode I get nothing. I took a test light to all the relay points and get power where I'm supposed to. I've swapped relay between A/C blower and fan and A/C blower motor work so I assume the relay is good. They were working a few months ago when I replaced the fan assembly.

What should I look at next?

Thanks Roy

anybody???

hows the thermostat look???

What are your indicators? How do you know they don't come on? Is engine temp guage in the red? Do you boil over at drive-throughs? Is a/c not working?

Cooling fan(s) are not commanded on by engine computer until engine temp hits 227 degf. which can only be had by an extended idle (perhaps 30 min) at 80 deg ambient. Fans typically don't run while driving.

Cooling fans do not come on until a/c head pressure hits 175 psi. is your a/c up to that?

To test, let the car idle with a rug over the front end- watch temp guage and see where fans do come on-- I do it with an engine scanner, and wait for fan(s) and monitor digital engine temp the whole time- primary fan comes on near 227degf, and secondary at around 237degf- seems hot- you bet, but that is how cars are designed now days fuel economy is first priority, keep fans off, less load on alternator, less load on engine, greater fuel economy.

This is all done so as to improve fuel economy, why have fans on when you don't need them.

You have already tested the fans by jumpering the relays--

I get this same question at least a dozen times this time of year. People go through winter with noticing temp guage is at midpoint - then all of a sudden it gets a tad warmer, but not warm enough to run a/c (fans would come on when a/c pressures rises) then they see the guage rise a smidge- get concerned. Summer comes along and they start using a/c everyday, (fans are on) and temp guage stays at midpoint again. So it is only when a/c is off and ambients are mild (Springtime) that these "no cooling fans" concerns crop up. But indeed, not a thing is wrong, just their interpretation of it is. This comes only from folks who have a temp guage-- never from those who have only idiot lights. Some are looking for things that are not an issue and spend lots of time and money trying to fix a problem that does not exist.

The reply by bccid is probably very accurate.

However, when i could not get my fans to turn on, i replace the thermostat and temp sensor, and that solved the problem. Not hard, but more time consuming than other cars I've tinkered with (must remove throttle body).

Although I could have released trapped air when doing this service, and I did replace old coolant with new 50-50 solution, I could be wrong. But I think the temp sensor was erratic.

Todd

97 malibu v6 137k

Only indication I can verify was that all was working fine when fans were replaced. I replaced the assy due to cooling issues, (weak motors).

Fan assembly was replaced a few months, at that time I let it sit at idle and fans came on after temp came up. Both primary and secondary fans kicked in. Now neither fan comes on, no other maintenance has been done to car. A/C does need to be serviced, low on freon but I assume that would not be cause for either fan to kick in. If temp is rising I would think one fan would kick in wether A/C was on or off?

I'm going to try to some new relays and temp sensor(already replaced once), and go from there again.

Thanks for replies.....

You can test to see if your ECM wants the fan on byt probing the ecm leg of the fan relay, does it switch to ground when fans are commanded on? If so, and fans are not on, your issue is downstream towards the fans. If not, then ECM has not commanded them on, or an input hasn't been interpreted correctly by ECM.

The whole trick to this analysis, is to know when the ECM commands fans on,,,it is a whole lot hotter than you can imagine.

Only thing I noticed was that the fans kicked on when the temp sensor was disconnected. After a few minutes they turned back off and gauge climbed but fans never came back on. Should I just try a temp sensor and go from there?

Only thing I noticed was that the fans kicked on when the temp sensor was disconnected. After a few minutes they turned back off and gauge climbed but fans never came back on. Should I just try a temp sensor and go from there?

Seems to me, you have just proven the system is working fine- unplugging the temp sensor is the fan test...ECM will turn on fans if it can't determine engine temp- this is a safety device so that engine doe not overheat if a failed temp sensor circuit.

So, does your car overheat, boil over? Why do you think it is not working properly? Temp gauge climbing is a normal response- does it go into the red zone? A scan tool will prove the engine is not overheating, even though gauge climbs.