HAVC System - Temperature Sensor Values

[Fresh Air Inspector]

Hello All,

Searched the threads but couldn't find any related to this issue (?).

Don't know if this is indicative of the Scorpio HVAC system; if I set the temperature at 20C (68F), as the engine warms up the air temperature coming out of the ducts is quite warm. However, once the interior warms up the opposite happens and the air becomes quite cool leading one to up the temperature display to 23C (~73F), or more. This has little if any effect on the vent discharge temperature.

The 'air distribution' doors all appear to be functioning properly. When I use the AC in warmer weather it appears to function correctly as the temperature does not fluctuate as it does in heat mode. I should point out that I have removed the 'flaps' in the centre vents (wood grain covered section), although this shouldn't affect the interior temperature versus the HVAC temperature setting.

I've checked the heater valve vacuum solenoid and it functions correctly. The heater valve appears to be functioning correctly. The ambient temperature sensor under the hood, on top of the HVAC housing appears to be functioning correctly (value changes with temperature changes). I haven't checked the interior discharge air sensor (lower housing, passenger side), or the interior temperature sensor (roof console).

The reason I stopped after the ambient air sensor is I couldn't find any information in the service literature on how to test these three sensors or any form of 'resistance value vs. temperature' table.

Questions;
1. Is this heat setting temperature issue 'normal' for the Scorpio?
2. If not, where should I be looking to solve the problem?
3. Does anyone have a 'resistance value vs. temperature value' table, or where to find it in the service literature?

[Ed Lijewski]

In my experience (an '88 and an '89) it's typical. "Normal"? I never owned a Scorpio from "new" so I can't say. But I have owned my '88 since 1995, so...typical.

I'm not a fan of the Scorpio automatic climate control system. The manual climate control system, as on the Euro Granada/Scorpio of the '80s and on the Sierras and the Merkur XR4Ti, is super easy to control and to finely modulate fresh/recirc air and heat and/or a/c as desired. And the effect of whatever change to those one makes is almost instantaneous. Not so for the Scorpio system where a short or long delay is normal.

The Scorpio system was SOTA in its day. That's all I can say for it.

YMMV

[brokencase]

You did not indicate what ambient was. Behavior of the EATC varies drastically with ambient when set to AUTO.

Naturally we would expect on cold start that the system will blow hot air until the cabin gets close to desired target.

It's a PID control loop, and it would not be a surprise if there was some amount of overshoot and the system response time is a bit slow.

If the EATC thinks it is really cold out it may go into defrost mode for a period of time before adjusting to target.

You should also notice that after a cold start the EATC waits a bit to allow the engine to warm up before turning the fan up to high speed. Not sure if this is a fixed time delay or if it is monitoring the exit air flow temp.

FWIW - I seldom run in AUTO.
If it is the Summer I will manually set to recirculate A/C and will set temp to 00F and fan on HI - this, because the Scorpio A/C never seems to put out enough to counteract the hot leather.

In the winter it is the opposite. I either need defrost so I will set temp to 99F and defrost on. Otherwise it is set to ECON and fan LO and temp 72F. As for the cold leather seats I now have uprated to heated seats.

All other cases - EATC is turned OFF. Moonroof is open and maybe the side windows down a bit - Radio is playing some late 80's music - Scorpio bliss.

I would not expect a failed thermistor (or out of spec). They are very reliable. Although a bad connector may be culprit. But if this were the case then you might have gotten an error code on the EATC.

In fact, if you don't see an error code and you know your vents are working, then I would say there is nothing wrong.

[Fresh Air Inspector]

Hello Ed, Brokencase,

Appreciate the feedback. Pity that this 'feature' is standard.

I always run the HVAC system in manual mode (ECON if AC is not needed), as I find auto has the fan on high more often than not. I find the fan noise on high, annoying to say the least.

Pity there isn't a solution to the temperature cycling as its a pain having to change the temperature setting every 15 minutes or so. Fortunately we don't drive the vehicle in the winter, they salt / spray brine on the roads here. So the car goes into the garage from early December until late April / early May.

Does anyone know exactly how the system functions? For example, is the vacuum solenoid for the heater valve on the passenger inner fender an on / off device or is it modulated / pulsed to control the flow of coolant? Also, is there a blend door that controls the amount of outside air that is directed through the heater core versus directly into the interior? Just trying to get my head around why the broad temperature swings with the factory set-up.

[Ed Lijewski]

I have no proof but I believe the HCV solenoid is either off or full on. Cabin vent air temp is modulated by controlled adjustments of the fresh/recIrc blend door.

Note: the Owner's Handbook says to only change the EATC setting by a single digit (e.g., 70* to 71*).

B.S.: If/When a driver or passenger feels the temp is off, they feel it in the order of 3-4-5 degrees. So moving the setting up/down a single degree and waiting for the EATC to adjust to that, then up/down a single degree again, and repeat, is sadistic.

YMMV

[brokencase]

Fresh Air Inspector -

I must admit that even though I do not set AUTO often I have never found it to be the case where I get wide cycling such that I need to adjust temp as you describe.

So it still may be possible that you have an issue somewhere.

I'm wondering if your Scorpio has had the "Air Discharge Temperature Sensor Relocation" TSB performed as part of the "M57 Rework". See attached. Notice item "H" - Reposition air discharge temperature sensor Provides improved in-car
temperature modulation. I have the full TSB regarding re-positioning the air discharge sensor. It is involved - a multi- page procedure. Let me know if you want it. I thought I provided all the Merkur TSB's and other files for Brad to post in the resource section. Not sure he got around to it.

Also notice item "F" Scorpios had bad speed sensors out of the gate. Ford eventually figured it out but many cars did not get them replaced. Not sure that the replacements that were installed were any better. Which is why I devised the Ford Ranger Speed sensor conversion circuit.

m57_changes.jpg (120.5 KiB) Viewed 2783 times

Also here is a useful TSB regarding EATC error codes...

eatc_codes_tsb.jpg (206.06 KiB) Viewed 2783 times

[brokencase]

Fresh Air Inspector et. al. -

PDF of the TSBs can be found here:
https://www.mediafire.com/file/1o9z21or ... s.pdf/file

It is text searchable.

[Fresh Air Inspector]

Hello Ed,

Appreciate the feedback. Did a quick check on the heater control valve using a vacuum gauge. It receives a vacuum signal until the AC is engaged then the signal drops to zero. I suspect the HVAC must restore the vacuum signal at regular intervals to ensure the set temperature is met.

Hello Brokencase,

Appreciate the 'library' of information. Amazing that Ford issued over 450 pages of TSBs for the Scorpio. I've downloaded the file and when the snow starts to fly come January I'll sit down and read through the documents.

Moving the air discharge temperature sensor is a bit of a challenge according to the TSB. The compete passenger lower dash panel needs to be removed to gain access to the sensor and drill the hole for the new location. Maybe in a week or two I'll pull the lower dash and perform the upgrade. I'll take lots of pictures and maybe do a write up on the process.

Thanks again to both of you.

[Ed Lijewski]

Vacuum gauge test on control of the HCV should be done sepsrately with EATC setting at Fresh Air and RECIRC mode, I think.

YMMV

[andyofcolumbusmerkur]

Just 450 pages? I thought it would be more.

[brokencase]

Fresh Air Inspector -
I would not assume off the bat that you have to re-locate the sensor. I am only mentioning it may be a possibility.

I would first try to determine where the sensor is presently. A good way to do that is to use one of those inexpensive borescopes that you can get for around $10 (on ebay) that plugs into your cell phone/tablet/PC usb port.

Like this...
https://www.ebay.com/itm/394267696258

You will find that these borescopes are very handy. You can peak into your spark plug holes and see what your cylinder walls look like. You can inspect the motorized vents. I actually connected a hose to the borescope that went to an aerosol teflon spray lube and I lubricated the Scorpio's blower motor bushings with it.

When I use it with my Windows laptop I used the free software from Oasis Scientific:
https://www.oasisscientific.com/downloads.html

I have an .ipk file for android called "USB camera 2.0" that I just email to the device and install.

These borescopes come with different cable lengths. I bought another real long one in case I need to inspect inside walls of a house or into pipes. I've never used it but a buddy of mine borrowed it to look into a drainage pipe.

[Ed Lijewski]

Vacuum gauge test on control of the HCV should be done sepsrately with EATC setting at Fresh Air and RECIRC mode, I think.

YMMV

I forgot to add this. On the XR (and likely also Sierra) the HVAC control for the HCV is an on/off valve on a vacuum line to the HCV (white valve in pic) which actuated On only at the full bottom position of the slider into the blue section; full bottom position is for maximum cool air. That position cuts vacuum to the HCV = best a/c cooling effect. Cabin temp modulation is by increasing/decreasing air flow through the heater core and/or opening/closing the fresh outside air controls via adjusting the slider positions or activating RECIRC.

Scorpios use a solenoid which appears to also be on/off only.

P1010223.jpg (64.82 KiB) Viewed 2693 times

YMMV

[Fresh Air Inspector]

Hello Ed,

My vacuum gauge testing was a 'quick test' to verify that the heater valve control valve solenoid was at least functioning. The plan is to run more in depth tests in the future. Would love to replace the HVAC control with a simple manual set up. I had a fully automatic system in my '81 Mercedes - a royal PITA.

Hello Brokencase,

I have an inspection scope with a 1cm (3/8") diameter camera combined with an 11cm (4.3") LCD colour screen. I'll have to see if it can get into the area behind the lower passenger dash panel area. Maybe I can get in there via the glove box. I find inspection scopes have limited use as it is often difficult to ascertain exactly what you are looking it. Especially if one is looking around in an unknown area - one struggles to find a known point of reference to help locate exactly what you want to see.

I had a quick look through the shop manual as to how much effort is required to access the discharge air temperature sensor. Isn't as bad as I expected, probably around 2 hours. Will update this thread as soon as I have news to share.

Thanks again to both of you.

[brokencase]

Just 450 pages? I thought it would be more.

The generally accepted story of the demise of the Merkur brand was that it was poor marketing and low sales.
I disagree. I think that the dealers just got to the point where they told Ford "Enough is enough, these reworks are killing us.". Just look at all the changes in that M57 rework above.

If you have a reliable car and sales are low, marketing can eventually fix that. But when the dealers turn on you it is over. The Xr4ti may not have had so many issues and was just a case of "throwing the baby out with the bathwater".

The only reliable electrics on the Scorpio was the EECIV, which was made in the USA. All the Euro electrics are fault ridden. The speed sensor, the melting defrost switch, the blower motor that cooks the transistor. The gauge cluster issues like the fuel gauge anti-slosh board, the open frame potentiometers in the tach failing. The a/c diode issue. The cycling door lock issue. The list goes on...

The Scorpio was just one of those first generation of vehicles with highly sophisticated electronics and had a lot of growing pains. So it was not a case so much of bad engineering as it was a case of engineers being overwhelmed. There is the flip side where they did a lot of nice things on the Scorpio as well.

The result of all this today is we have an orphaned and rare vehicle, at least on this side of the pond. It also means that an original vehicle becomes somewhat nebulous. Some Scorpios were re-worked and some were not. Modifications are often mandatory to overcome original shortfalls. Eventually you will have to replace the speed sensor with something else.

Collectable? Beauty is in the eye of the beholder and rarity does not always equate to value.

For me it is the styling and ergonomics. I have a hunch that the Scorpio stylists were heavily influenced by Syd Mead.

[brokencase]

Appreciate the 'library' of information. Amazing that Ford issued over 450 pages of TSBs for the Scorpio. I've downloaded the file and when the snow starts to fly come January I'll sit down and read through the documents.

More stuff to read through this winter...
https://www.mediafire.com/file/sivr5rgc ... s.pdf/file
https://www.mediafire.com/file/gasxo39q ... V.pdf/file
https://www.mediafire.com/file/mry1h46u ... V.pdf/file
https://www.mediafire.com/file/9z39ot7c ... V.pdf/file
https://www.mediafire.com/file/cguozqpj ... 1.pdf/file
https://www.mediafire.com/file/t9gjm5ur ... 2.pdf/file
https://www.mediafire.com/file/dma94oh2 ... 3.pdf/file
https://www.mediafire.com/file/luurozy9 ... f.zip/file