View Full Version : Radiator fan low speed issue?

08-18-2017, 09:34 PM
I've been trying to figure out if I have a radiator fan problem with my 95 SC. It seems to me that when the fan kicks in, it goes straight to high speed. It doesn't seem to match the specs in the service manual. Using an infrared temp gauge on the radiator by the upper hose nipple, the temp gets to 239F when the fan finally kicks in. It sounds like what I would expect to be high speed. It does drop the temp 10 degrees before it turns off. That cycle continues as long as it idles. I never see any other speed. The fan is supposed to kick into low speed at about 210F (if I remember right), and hit high speed if the temp gets to around 230F I have replaced the IRCM, feeling certain that would solve the problem, but no. Interestingly, though the fan does the same thing whether the AC is on or off, the temp gauge on the dash is less than 1/4 of the way up with the AC on, but with the AC off, the temp gauge keeps climbing. I get that the AC fan would likely help cool the coolant as well, but I don't get why the gauge temp doesn't react the same as the radiator temp.
Has anyone ever had the low speed fail because of a bad cooling fan motor? Can the motor lose just one speed while still working otherwise?
Note: I have also replaced the temp switch and gauge temp sender.

Any ideas??


08-19-2017, 07:20 AM
The motor can lose one winding, yes.

You can also lose one connector inside the power connector, which could cause one winding to quit.

I'd suggest monitoring the voltages on the power connector - are you getting power at about the 210F mark? If so, and low speed doesn't kick on, I'd say bad fan. If not, then back track using the wiring diagrams in the EVTM and find out where it's NOT coming from (could be a bad IRCM still; could be a bad IRCM connector; could be a bad ECU; could be almost anything. I'll bet the fan motor and/or the power connector first, though, without testing.)


XR7 Dave
08-19-2017, 07:31 AM
As Ralph said, fan motor is #1 suspect. You can check for power at the plug though because it's also possible to lose a relay in the IRCM. The 95's don't usually have connector issues because the plug goes directly into the fan motor rather than having a midstream connector like the 89-93's do.

08-19-2017, 02:16 PM
Thanks guys. I'm going to a local cruise night tonight, so I'll check it out after.

Btw, does anyone have any idea how many cylinders the SC engine has so I can post some messages. lol

08-19-2017, 03:17 PM
I was just shopping around in case I have to buy a fan motor and found it interesting that this item, VDO PM9003, is listed as a direct replacement to match all OEM functions, but in O'Reilly's description for that exact same part number, it specifies that it's only 1 speed. hmmm I realize many descriptions are wrong, but it doesn't exactly instill extra confidence.

08-19-2017, 03:26 PM

Recent discussion about that here:


08-19-2017, 03:56 PM
Thanks for the link. The most positive thing I saw was that rickbtbird said that all circuits worked as expected, but I wan't sure if that confirmed that the motor was actually running at 2 different speeds or if both wires each ran the motor on high. I'm nowhere close to overheating, so I have plenty of time to figure this out.
I certainly welcome any more input.


08-20-2017, 05:47 PM
I made an extension harness that allowed easy access to tap for reading voltage. I started it with the AC on. The fan was running and I got 9.8v on the bottom terminal at the fan, 13.3v at the middle terminal, nothing on the top one.
Turned off the AC and after a minute or so, fan off and no voltage. I let it get to temp. At 242 degrees, the fan kicked in (seemingly in high speed) and the voltages were essentially the same as before. At 220 degrees, the fan turned off. The cycle continued like that. I turned the AC back on, the fan came on and the temp dropped down to 190 and settled there with the fan never turning off until a minute after the AC was turned off again. I also noticed that the pusher fan never came on...another issue I didn't know about.

Can anyone make out any useful info out of that? Any ideas where to go next? Are the voltages correct or is that what would be expected for a motor with a dead winding?...or maybe a replacement motor with only one speed?

I'd appreciate any help I can get.


sam jones
08-20-2017, 07:34 PM
Good afternoon

I would check the temperatures with the IR and a live feed scanner. What does the EEC see? What is the rating of the thermostat are you using? Is the thermostat working correctly? See attachments below.





Check for corrosion and or damage in the connectors also.

Next I would pressure test the cooling system. Is the radiator cap seal cracked? How old? A problem I discovered is coolant leaks at the water pump 6 o'clock postion to the oil cooler "J" hose and the top inlet hose fitting at the radiator. The radiator inlet fitting can become misshapen over the years (from tighten the worm clamp) that leakage is highly probable. Tighten to correct only makes it worse. I used GATES 32954 {#42954} Thermoplastic - Size SB54 (Nominal Hose I.D. 1-3/4", Fits Hose O.D. 2" to 2-1/4") Info
clamp to correct my leaking/ overheating issue. See attachment below.


For the oil cooler hose I had to cut the factory J hose crimps and remove the hose. The replacement hoses was double clamped to prevent future leaking.

Hope this helps and Good Luck.

08-20-2017, 11:25 PM
Thanks for all that info.

After taking care of a couple of minor leaks between the timing chain cover and engine block this winter, the cooling system is holding pressure perfectly. It's a brand new 180 degree thermostat. Both temp sensors and the water pump are new. The IRCM is new and made no difference in the fan function. Under normal driving conditions or idling with the AC on, the temp never gets as high as the "O" of "NORM" on the gauge. I'm convinced that if the low speed would kick in, the temp would likely never get above the intended 222 degrees. I think it reaches 240 degrees only because it has to wait for the high speed parameter to be reached. Nothing has any level of corrosion and all connections seem solid. I'll have to double check, but when I looked, the harness showed no sign of wear, chafing, pinches, or any other sort of damage.

I'm really interested to know what voltage I should be reading on each of the terminals in the connector that plugs into the fan when the low speed kicks in and when the high speed kicks in. Should any of the terminals ever read less than battery voltage as one of mine does when the fan kicks in, while another shows full voltage? I would have thought that with the low speed active, one terminal would show 12v and in high speed, the other would have 12v. Or, in low speed, one would have 12v and in high speed 2 of them would have 12v. What confuses me is that every time the fan is on, the center terminal has over 12v and the bottom terminal has under 10v. Should the third (top) terminal ever see any voltage. Mine never does. I assumed it was the ground.

I am going to borrow the infrared gauge from work tomorrow to make sure my gauge's calibration isn't off. If the terminals' voltages are normal and my infrared gauge is off, then maybe the low speed is working fine and my temp has never gotten high enough for high speed. I guess that's possible. I really need to know what those terminals should be reading in a fully functioning system.

08-21-2017, 12:46 AM
It's a brand new 180 degree thermostat

Sorry if I missed it - you have a chip that includes reprogramming the fans to go along with that stat? Why did you use a 180 instead of the stock, say, 192?

BTW, that 3rd wire is ground. I don't know the volts for the other two (and only have working knowledge of early systems), but I've always assumed they are both 12v out of their respective relays in the IRCM. If you're seeing much less in either example, perhaps the IRCM has a fault and/or is the wrong one and/or there is something else on the lower volt circuit that is draining the load and/or a faulty ground is restricting full 12v.

The IRCM diagrams I checked (early and late) don't show anything other than inverters path'd to the EEC - they only show straight thru each relay to the fan circuits.

08-21-2017, 05:45 PM
First, to answer your question, I changed the thermostat while I had the cooling system open this winter and chose the 180 because my plan is to use a chip that recommends that rating. I didn't want to have to get into the cooling system again.

As for the fan...I solved the problem by realizing I couldn't trust my infrared gauge. I compared it to the one we use at work and it turns out mine read 20-25 degrees hotter than it really was. Factoring in that little detail, it turns out the fan WAS kicking into low speed, at the correct temp. It never got hot enough for high speed. I've gotta say, low does push a lot of air.
There is nothing wrong with the fan. I spent my time and some money and wasted other people's time here because of a low quality tool. I do appreciate everybody's input. It's good to know you guys are so willing to help.

I feel a bit foolish. I should have known better. But I'll live. :-)

On to my next fun project.

08-21-2017, 05:56 PM
Good that you got it sorted in any case - thanks for the follow up an enjoy your ride ;)


08-22-2017, 01:21 AM
Now that I'm thinking about it, if the circuit doesn't have any diodes, it's entirely possible that the 9.8v I was reading was a back feed of voltage being created by the high speed windings in the motor. When I first installed the intercooler fan, I had an LED to show the fan was on, with no diode in the circuit. When I turned the fan switch off, the LED would fade slowly as the backfeed from the fan motor dropped off as the fan slowed down.
Just a thought.