'90 Plymouth Grand Voyager; no radiator fan

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  #1  
Old 05-07-10, 03:50 PM
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'90 Plymouth Grand Voyager; no radiator fan

New coolant temp senders (2), new radiator fan relay, ground relay to battery negative and fan roars to life. Computer only shows 12v when it grounds, apparently not enough to close the relay. Two computers under the hood; one on firewall, one on left fender. Which is the engine computer? Anyone ever seen this before? Thinking maybe corrosion at connections or a poor computer ground. Any other direction? Thanks in advance - Chris
 
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Old 05-07-10, 06:46 PM
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If your head gasket is starting to go, in the early stages, or for whatever else reason you are losing coolant through the engine or heater core leak, and your radiator system has lost the ability to draw coolant back out of the reservoir when it cools backdown, an air bubble can form behind the stat. And this causes the sending unit to not sense hot coolant, and the fan may not come on.

Make sure you do not have that issue I speak of. Make sure coolant level not slowly disappearing over time. Since you have an old Chrysler product, your vehicle is ripe for this scenario. This is why I now drill a hole in my stat to allow passage of trapped air.
 
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Old 05-07-10, 07:01 PM
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Ok...ok... SLOW DOWN.........



There are two styles of relay used in those years....One is a 1x1 inch little black cube, the other has a metal "CAN" and looks like an upside down "Baking Pan"....Which do you have????

Second..... The fan relay gets "Grounded" by "SMEC"( What Mother Mopar has named your engine computer). So 12v at the ground terminal of the relay is NOT what you want to see......

Real simple ....Unplug the coolant temp sensor while the engine is running....The fan should come to life in about 10 seconds.....That will test the relay, fan and power supplies all in one shot. Post back with the results.
 
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Old 05-07-10, 07:04 PM
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oops.....Almost forgot....Left fender is SMEC, firewall is EATX...(Trans Control)

Is this a 3.0L?
 
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Old 05-07-10, 08:12 PM
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Okay, I need to clarify a little. The blue/red wire that goes to the ground (control) terminal on the relay - when I set my multimeter on 20vdc, poke the red lead into the battery POS post and and the black lead into the connector on the blue/red wire, I read 12v, rather than battery voltage (13.2vdc or better), indicating (to me, at least) a weak ground. This is done with key on, engine hot. And if I ground that same relay terminal straight to battery NEG, the relay closes and the fan turns as smoothly and quietly as anyone could ask for. And radiator stays full on coolant.
Unclediezel - When you mention unplugging the temp sender, do you mean the single-wire sender on the right side of the forward head, or the two-wire unit by the thermostat? Thanks again for the help - Chris
 

Last edited by CMil; 05-07-10 at 08:14 PM. Reason: Information left out.
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Old 05-07-10, 08:14 PM
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oops.....Almost forgot....Left fender is SMEC, firewall is EATX...(Trans Control)
 
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Old 05-07-10, 08:22 PM
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two wire at T/stat.

*** Toss the Multimeter****

A plain old "TEST LAMP" is what you need here. Under load, it is very Normal to show a voltage drop.

Just for giggles, Swap that relay into the position marked "ASD" or "Auto Shutdown". If the van doesnt start after the relay has been moved....Replace the relay.
 
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Old 05-08-10, 05:34 AM
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I've never been able to get a straight answer on the order of the relays on the fender. There's one of the black "box"-bodied relays furthest in back, by the diagnostic connector, then four "can"-type relays in a row going forward. Noone has ever been able to clearly identify the function (in any sequence) of all these relays. Any input here? Thanks aagain - Chris
 
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Old 05-08-10, 06:16 AM
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Quick update - the relay that shares its mounting bolt with the radiator fan relay has a different terminal "footprint" than the fan relay. Voltage at two of the terminals on the "hot" side of the fan relay connector when disconnected is 12.5 engine off, 14.4 engine running. Voltage at the ground terminal when disconnected is 12.5 engine off, 14.4 engine running (again, checking the terminal as a ground). And when I disconnected the 2-wire temp sender, I never got fan. Now, what I found a little strange is that the SBEC is calling for radiator fan even when cold. Also, when I unplug and reconnect the ground connector at the relay, the relay can be heard to click and the fan starts to turn, but the relay never stays closed. Does this use a special-purpose, dealer-only relay, rather than something sold by such-and-such auto parts store? If I can find a relay to stay closed, I guess I'd rather see fan all the time than never at all. Where to go from here? Wire in a toggle switch, monitor temp and manually control the fan? Add a controller just for the fan relay? Replace relay and SBEC? Thanks for help so far - Chris
 
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Old 05-08-10, 03:13 PM
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I wired in such a switch on my old Dodge.

Bought 30 amp, 10 gauge fuse holder with 6 inches of wire on each each end, at one of the biggest national chain auto parts stores.

Then wired it direct to battery by spreading battery clamp, inserting the wire, then retightened clamp.

Then on the other side of the fuse holder, I wire nutted a few feet of 10 gauge wire to it and ran it through an existing firewall hole to a house switch under the dash (you could use a 20 amp one).

Then ran another 10 gauge wire from the other terminal on the switch out through same hole and down to the fan.

I also had bought from auto parts store a jack connector that has two jacks on each end of a shared wire - one male version , one female version. Why? Because then I could unplug my existing OEM jack from my fan, plug in the one jack-end of that double jack I bought, and then plugged the jack wire from my harness into the other end of the double jack.

Then I cut that shared double-jack wire in half. That is where I then tied the 10 gauge wire returning from the switch (so that be 3 wires in a wire nut). This joinery created a system in parallel with the automatic fan system, so that either the fan would still be able to come on automatically, or I could choose at any time, to turn it on. Because basic wiring is easy for me, once I had the parts in hand that I said I bought (the 30 amp fuse holder with short wires attached to it, and that double jack on each end of a shared wire, and a small spool of stranded 10 gauge wire(red), and the light switch) I did the job in 20 minutes, tops!

Then I experimented with fuses in my fuse holder. I started with 10A. But after the fan ran a bit, it blew. So then I went up to a 20A (remember the fuse holder wire and the wire I ran is good for 30 amp), and that never blew, even with the fan running constantly for 20 miles straight. I did longer and longer trial runs, making sure the fan motor would not overheat. It never did. Pretty nifty little back up system that could save you an engine! (But that is only as good as your thermostat being able to open. If you have an air bubble behind the stat, the stat may not open unless you bleed it out, or you drill a hole in it!)
 
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Old 05-09-10, 06:07 PM
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Thanks, ecman51. Sorry, Unclediezel, I just now caught your engine question. No, not a 3.0, but a 3.3. Difference in diagnosis/prognosis? Thanks again - Chris
 
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Old 05-10-10, 04:24 PM
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No, not really........

What I do remember Clearly was "Z1-Feed" which is unique to the ASD relay I discussed. It is a dark green wire with a black tracer. it feeds Injectors , fuel pump and Ignition coil with 12 volts.

Im not sure of the order, but A/C, Starter, ASD, and Cooling fan, for the cans.
 
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Old 05-10-10, 07:48 PM
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Dark green, black tracer. Is that the power wire coming back out of the relay to the devices it powers, or the control ground? Not really critical at this point, as the van runs fine, just doesn't call for cooling fan. Is there a place on the engine where I can screw in a temp switch to throw a ground for the fan relay?
 
  #14  
Old 05-23-10, 10:35 AM
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I installed a universal fan controller from autozone. Comes with fuse and relay, temp switch, easy install. Cheaper then replace computer.
 
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Old 05-23-10, 04:54 PM
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Originally Posted by allen1 View Post
I installed a universal fan controller from autozone. Comes with fuse and relay, temp switch, easy install. Cheaper then replace computer.
Why would such a set-up be needed or prefered over say the already existing factory system? If say the sending unit is bad, or the relay is bad....why not just replace the thing that is bad? Why get an entire new kit?
 
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Old 05-24-10, 12:50 PM
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Well in my case the computer was not turning on fan when it was suppost to. Relay, temp switch, all were replaced. computer was at fault. So a $12 kit is cheaper then a computer
 
  #17  
Old 05-24-10, 06:19 PM
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Similar situation - ECM is calling for fan all the time, but the ground it sends is too weak to pull the relay in and keep it in. Think the fan controller is going to be the way to go. Right now the manual switch is working fine.
 
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