[bobjob]

1999 olds shiloutte van ,3400 V-6. new water pump,thermostat, belt, &pulleys. 3 relays seem ok.fan won't come on. cant find switch to check.
every thing goes thru ecm. what can i do now??
too broke to just start changing parts!!
help please...

[cobalt327]

Well, I would start by seeing if the fan motor is good. Jump the (disconnected) terminal from the fan to the battery and see if it motors good and strong. Try it from several different places that it stops, to rule out a bad segment.

If it runs good, start tracing wiring. It will have a temp switch (usually near the water neck or sometimes into a water jacket or the radiator itself, occasionally, depending on the make/model) as well as a relay- plus all the connections, terminals and wire runs to hook it all together.

Worst case scenario- if you have to drive it and can't afford to properly fix it (although it shouldn't be a total budget-breaker)- and the fan motor's good- wire a relay and toggle switch to manually operate it. Not an ideal solution, but it'll keep you going until you can fix it properly.

[joe_padavano]

Originally Posted by cobalt327

If it runs good, start tracing wiring. It will have a temp switch (usually near the water neck or sometimes into a water jacket or the radiator itself, occasionally, depending on the make/model) as well as a relay- plus all the connections, terminals and wire runs to hook it all together.

Not necessarily. Newer GMs use the computer (via the coolant temp sensor) to operate the electric fan(s). My 1999 crewcab dually is set up that way. You really need a factory service manual and wiring diagrams to properly chase the wiring on something that new.

[rtyauch301]

first things first go out side start the van turn the ac on max and see if the fans come on they should. let me know if they do then i can help because like said earlier the fans on your van are run through the computer.

[cobalt327]

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[bobjob]

fans not coming on with a/c on...ran out to casa grande (45 miles one way) and back in 100 deg. weather..(90 miles total). guage went past 1/2 way point.. checked fans...not running..a/c was on...relays seem good.. what next???

[T-bucket23]

Coolant temperature switch is in front of and below the throttle body.
I would test the fan by jumping it at the relay.
I have attached a couple pictures for you. Hopefully they will help.
I would take a hard look at the ground that is listed on the diagram and the 2 control signals and work out from there. I am assuming you checked the maxifuses.

[rtyauch301]

Originally Posted by bobjob

fans not coming on with a/c on...ran out to casa grande (45 miles one way) and back in 100 deg. weather..(90 miles total). guage went past 1/2 way point.. checked fans...not running..a/c was on...relays seem good.. what next???

although your fans aren't coming on your temp shouldn't rise when your driving. so first things first lets check those fans if u cant figure out how to do it the way t-bucket said the 2 electric fans shoud come off as a unit the entire shroud. its simple just hook them up 2 a battery now if they work then you need 2 trace down your problem. check the connection at the relay with a volt meter do it with the ac on so you can make sure the the wire that throws the relay works if not you need to trace that wire down make sure its not broken if its working then your relay is bad. now for the rest it appears as though your temp is coming up when driving and not just when sitting still. i had this very same problem the temp would come up over the half way mark n just above that next line in my case and this is often over looked the radiator cap was bad it was opening to soon and letting water out not alot but just enough these cooling systems on these 3400's don't work well without pressure so replace that cap their only about $2. also did you bleed your water system often over looked on these motors air pockets will make these motors seem hot its a screw off of a black pipe just over the water pump loosen it with the motor running and the radiator cap on and the engine running when a stream of water comes out without any air. remove the radiator cap when you get the steady stream add water tighten the bolt then install your cap then you can turn the engine off hope this helps an dgood luck

[T-bucket23]

Its unlikely that both fans went bad at the same time. The most likely cause is that ground is rotted off or the fuse for the whole system is blown. Going down the road most vehicles dont rely much on the fans as a good amount of air gets forced through the radiator. Of course a lot of this depends on grill design and that all the plastics are still in place. On a 90+ day with the a/c on the fans will probably still be needed.

Again my bet is on the ground or the fuse. If the fuse is blown it could be due to a bad fan or a shorted wire. I have worked on a few of the GM vans and the wiring leaves a lot to be desired.

[bobjob]

thank you for all the info... i'll check it out ..i'll let you know what i find out....
already bled system,,replaced cap,, and all the usual stuff... i know electrical,, but nothing on newer vehicles..guess it's time to learn...
i really appreciate the quick crash course in computer controlled auto -101-...

[rtyauch301]

Originally Posted by bobjob

thank you for all the info... i'll check it out ..i'll let you know what i find out....
already bled system,,replaced cap,, and all the usual stuff... i know electrical,, but nothing on newer vehicles..guess it's time to learn...
i really appreciate the quick crash course in computer controlled auto -101-...

hahah and i do better with newer ones with my old one i feel like im poking around with a stick trying 2 find the problem.

[bobjob]

everything has electrical glitches !!!
now all of a sudden,, fans magically start working... same day,, computer takes a crap...and now it's a working.. may be due to over 30+ days of 110+ degree weather..
van still too hot for me,,just under 1/2 way with a/c on..haven't tried shutting it off yet.. need to replace both front power window motors..they quit during cold spell-- around Christmas, it gets almost to freezing,,35-40 in morning..i know,, but in AZ. that's cold..
I read in posts here that mixing orange and green coolant is not good,,gums up or something.. I used orange when i replaced heads 1&1/2 years ago,,and i used green later.. PROBLEM??? should i use a flush and just use green?? orange costs too much,, had to replace heads because of erosion on aluminum heads were leaking ,worn and pitted at water jackets.. at every place it flowed.. right out motor.. had to buy new heads..
SO,,, flush and add green or orange?? REMOVE radiator then flush?? flush with clean water,, run it for 100 miles,, flush with water again 2-3 times till clear,than add coolant?? looking for opinionon what to do next.. whew,, do i ever hate these newer cars.. if i spent this much time on my toys,, i'd be almost done by now..my '63 chevy carryall,,drove for 15 years with no trouble...stopped it for upgrades,and bought this van for trouble free driving..HA HA.....

[302 Z28]

Flush and remove all traces of coolant then go with either green or orange, not both. The green stuff is now available in extended life versions, so that is what I have been using. Use distilled water to thin the coolant or buy the already thinned stuff. It is very important that you do not use tap water.

The above comments about the computer controlling the operation of the fans is "dead on". If the computer is not seeing the engine temperature as high the fans will never come on. Correct that problem first if that is what is happening.

Vince

[T-bucket23]

Just under half way is perfect. Did the fans start working after you replaced the computer?
As far as the anti freeze, if you don't knock out a freeze plug or at least open a block drain you will never get it all out. I agree with Vince, buy pre mixed green style and be done with it. The Orange (Dex-Cool) is nothing but problems.

[Bryan59EC]

I had an electrical spike in my old 88 Bonneville.
Anything that was turned on when it spiked was pretty much destroyed.
All lamps
stereo
instrument panel
ignition system.

Everything got real bright---then the car quit---in the middle of Wyoming in febuary.

Got everything working again except the engine cooling fans----they never did work on their own again.
Drove it over a year in Salt Lake without fans at all----just kept the car moving.
When I finally decided to do something about them, I just ran a jumper across a connector that had something to do with the AC.
Fans now on all the time the key is on.

Sold that car over 5 years ago------still running around SanAntonio.