Temp. getting hot?

[bobinkski]

Hello, My new problem is the coolant temp. Did some searches on this and may have helped. What happens is the temp. goes up when stopped and idling. AC works OK, Drive at 60-70 mph temp is normal, at idle temp goes up and both low and hi fans turn on until temp goes down. The searches I did mention the Temp. sensor, the dropping resistor and the CCRM. The van is a 96 with 3.8. Any help would be great. Thanks.

[Selectron]

As a starting point, with the engine running but before it reaches normal operating temperature, I'd check to see if the fans operate when you switch the A/C on.

[Ed_Strong]

Check for proper level of antifreeze...

On a side note, I had a Chevy Cavalier that did the same thing and it turned out to be the fan motor wearing out. The fan would actually function as normal, but the motor was too weak and couldn't move enough air to keep the engine cool. At plain sight it would look like it was spinning the fan at normal speed!

[bobinkski]

Coolant level is OK, both fans run at the same time and run good. Noticed the dropping resistor wire leads are corroded, I may think it is that do to only the temp goes up when AC is on.

[Selectron]

If the fans switch on when the A/C is switched on, but with the engine not yet up to normal operating temperature, then that indicates that the low speed cooling fan circuit is working. Doesn't guarantee that it's working within spec., but it is at least working. I'd be wary of disturbing that resistor if it's an old one, because they become brittle and the ceramic casing cracks, and it's liable to crack further when handled. If your fans are running at a good speed then chances are the resistor is still ok but it's difficult to say because we don't know the resistor value. All we do know is that it's very low (less than one ohm), but it can't be measured accurately with a conventional digital multimeter - there was discussion of it and some photos in this thread, which you've probably seen.

The two fans are wired in parallel, so if one fan operates then they both do - they always operate together. I believe the fans are triggered under three conditions:

1. When A/C is switched on, and vehicle is running below a certain speed.
2. When engine temperature exceeds a certain threshold, the low speed cooling fan circuit is activated (by the PCM).
3. If engine temperature continues to rise above another, higher threshold, the high speed cooling fan circuit will be activated by the PCM.

The low speed circuit feeds the two fans via a resistor, so a portion of the system voltage is dropped across the resistor, the fans receive a reduced voltage, and hence operate at a lower speed.

The high speed circuit feeds full system voltage directly to the fans (no resistor) and hence they operate at full speed.

I'm not convinced that your problem is electrical in nature - if it is then it would almost certainly be the dropping resistor, but it could be so many other things - blocked radiator fins, poor coolant flow, etc.

On Searcherrr's mammoth thread he will have measured voltage at the fans when the low speed circuit was active, so I'll go and dig out the voltage reading. We don't know the resistor value and even if we did, it can't be measured accurately, but checking voltage at the fans is a way of indirectly determining if the resistor is too high in value - if it is then the voltage at the fans will be low. That's a '95 by the way - not sure what year yours is.

[Selectron]

No, the voltage at the fans appears to be the one measurement which is missing from that thread. If you have a multimeter you could try measuring the dropping resistor's value - the result won't be accurate but you could check and see if you get a reading which is broadly in line with Searcherrr's reading of around 0.3 ohms or less.

If you do that, then before measuring the resistor, touch the meter's probes to each other and note the value - typically around 0.3 ohms. Then measure the resistor, and subtract the probes' resistance from the obtained reading.

[bobinkski]

Well I was going to check the ohms across the resistor and the wire lead broke off. I did mention that they looked corrroded and they sure where. All I did was to touch it and they broke. I ordered a new resistor from www.forddirectonline.com/parts for $60. Ford dealer wants $80.

[bobinkski]

Took out dropping resistor and ceramic cassing is cracked and broken at the 2 leads wires. The one that fell off shows signs of sparking from breaking off during driving the van. There is no continuity at all and the 2 leads are badly corroded.

[Selectron]

If the leads were so very fragile then there's a good chance their resistance had increased, regardless of whether the resistor itself was still within specification or not. That would have the effect of reducing current to the fans and causing them to run slower than intended. Hopefully a new resistor with new leads will restore correct operation and fix your overheating problem.

[Selectron]

If you want to use the van before the new resistor arrives, it will overheat to some extent for sure, because when the first (lower) temperature threshold is reached and the PCM instructs the fans to switch on at low speed, nothing will happen. Same if you switch on the A/C - the low speed cooling fan circuit should activate but nothing will happen.

In both cases, no cooling will happen until the second (higher) threshold is reached, upon which the high speed cooling fan circuit will be activated and the fans will indeed run at that point.

So I'm going to suggest that you fit a bypass wire in place of the resistor for a few days, just until the resistor arrives, and that way your fans will still operate. I want to have a look at the wiring diagram first though so I'll go and make a cup of tea and check the diagram, and I'll post again later.

[Selectron]

Ok I had a look at the diagram, and fitting a bypass wire shouldn't be a problem. The low speed relay and high speed relay (located within the CCRM on your '96) are both rated at 40 amps, so they can both carry the current for full-speed operation. (I wouldn't recommend this for later models without the CCRM because when they made the change to external relays, they used different relays for low and high speed, and so the low speed relay likely won't be rated to carry the full current).

So, you've unplugged and removed the resistor, with its damaged leads and connector attached. In the van, that leaves you with a connector with two terminals, which is not connected to anything. I'd take a short piece of wire and bridge those terminals to each other. Make a secure connection - must be secure to avoid sparking and resultant heat damage - and then wrap it in insulating tape so it can't short to anything else.

When the engine temperature reaches the first (lower) threshold, the fans will switch on, but will run at full speed instead of reduced speed. This will quickly reduce the temperature and after a while the fans will switch off. Or when using the A/C, the fans will run continuously at full speed for as long as the A/C remains on - this might lead to the engine overcooling somewhat, but I'd always choose that in preference to allowing it to overheat.

The only fly in the ointment is that the low speed cooling fan fuse (fuse H, engine compartment fuse box) is rated at 40 amps, whilst the high speed cooling fan fuse (fuse B, also in the engine compartment fuse box) is rated at 60 amps, so there's a chance that fuse H might blow if asked to carry the full fan current. If it did then I'd temporarily fit a 60 amp fuse in its place, and then when the resistor has been fitted, put the correct 40 amp fuse back in there.

If you don't need to use the van for the next few days then no problem, but if it was my van and I was going to use it then that's what I'd do. It's only a suggestion though, which you can follow up on or not.

[bobinkski]

Selectron, thanks for the help. I wondered if I can drive the van wiyh the resistor removed. I have 3 cars and the van can sit while I wait for the new resistor. I will update when it comes and I install it.

[bobinkski]

Well, I installed the new dropping resistor and took the van for a test drive. Opened up the hood and looking at everything as the engine is running and all of sudden there was smoke coming up from the firewall area. I turn the van off. Restarted it up and ran for about 5 minutes and then more smoke came up from the firewall area. Great now what? The resistor is mounted behind the head light, not at the fire wall. Did the new resistor burn up something else? Never a dull moment around my Windstar!

[wiswind]

"firewall area", which side?
If driver side......check out the brake pressure switch on the bottom of the master cylinder for leakage......on my "cheap and easy list".

If elsewhere......track down the source of the smoke......something dripping onto the catalytic converter? or other hot exhaust part (including the rear exhaust manifold)?

Best of luck in tracking it down.......and I know you will.


As far as the temperature at idle.......(I thought I posted a response earlier, but I don't see one now),
When stopped......or in stop and go traffic, particularly in HOT weather, I set the climate control controls to a setting that activates the A/C.
What this does is turn the radiator fans ON.....and KEEPS them on whenever the vehicle is not moving at something like 45mph or so.
This keeps the coolant temperature (and motor) at a cooler, more constant temperature.....and VERY IMPORTANT, helps to keep the transmission fluid cooler (particularly if you have a auxillary transmission cooler).

[bobinkski]

I should of said it smelled more like electrical smell, not oil or antifreeze. Nothing is leaking, and the smoke was on the passenger side.