88R 12-16V Thermistors

The temperature gauge in the NB Fairlane has been over-reading. After confirming it was not overheating. checking the wiring, improving ground connection and changing the sender I found that it was the gauge (i.e. when the sender read 70 ohm the gauge was over normal near the red when it should have been exactly in middle of normal - if I read the resistance at the sender or the plug on the back of the gauge). I have the factory manual that gives gauge positions and resistance readings.

Some times the gauge reads OK and accurate but when the cabin temperature gets warm it plays up - annoying as I was usually working on the car in the evenings and the fault wouldn't show so I started taking my Multimeter with me and checking the sender's resistance whenever the gauge said the engine was hot and tracked it down that way.

I dismantled the VDO digital gauge set tonight have found the fault. There is a brown linear resistor type component on both the fuel and temp gauges marked 88R the one on the fuel gauge has 88 ohm resistance while the one on the temperature gauge reads 56ohms at a room temp of 22 degrees C. I suspect these brown linear components are protective thermistors and the one on the temp gauge is no longer stable. Can anyone confirm they are thermistors (or advise otherwise) and tell me a source for a replacement (tried RSComponents, Farnell, Jaycar, Altronics and Worldwide Electronics sites so far with no luck).

Can I join lower R rated thermistors in series or put a resistor in series with a suitable lower R rated thermistor? Other than voltage and ohms I will be sort of guessing the specs for a thermistor anyway.

If not I suspect I will have to buy a whole new gauge if Ford still have stocks or more likely go looking for a whole new gauge set with a working temp gauge.

For car nuts that think they know Ford model series; yes there is just one NB model Fairlane. see

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It's an ex Ford prototype so it also had a gauge set and sender unit from a later model just to confuse things further.

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aussiblu
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I'm starting to think it might just be just a 88R wire wound resistor.

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On Sat, 07 Mar 2009 15:47:53 GMT, "aussiblu" put finger to keyboard and composed:

Some dashboards have a 10V regulator for the instrument cluster while others use unregulated battery/alternator voltage. Maybe your 10V regulator fails intermittently and delivers the full 12V or 14V to the cluster ??? Some gauges incorporate a 5.1V zener. Does yours?

Could you post the "gauge positions and resistance readings" as stated in your factory manual?

FWIW, I have a Ford Registered Technician Technical Training Bulletin # 112 which describes the Electronic Instrumentation for the XF Falcon and Fairmont. This model series used a capacitive fuel sender and a resistive temperature sender.

The specs for the cross coil moving magnet temperature gauge are:

ohms reading

--------------- 220 cold 70 midscale 39 hot

If it helps, I could scan the relevant pages for you.

- Franc Zabkar

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The specs are the same as the XF temp sender.

i.e: ohms reading

--------------- 220 cold 70 midscale 39 hot

"Some dashboards have a 10V regulator for the instrument cluster while others use unregulated battery/alternator voltage. Maybe your

10V regulator fails intermittently and delivers the full 12V or 14V to the cluster ??? Some gauges incorporate a 5.1V zener. Does yours?"

Sounds possible although nothing is show in the circuit in the factory manual - every think seems controlled by a chip in the gauge set simply called the "electronic control module". I don't recall seeing any regulator but I I will dismantle it again when I have a chance and have a look (needed to put it back together so the missus could drive it).

The fuel sender is resistance based in the NB.

It would be very much appreciated if you could scan the relevant pages of the XF tech training bulletin for me as it might help me sort it out. Thanks

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Sorry I should wake up before posting that should read:

"Sounds possible although nothing is shown in the circuit in the factory manual - everything seems controlled by a chip in the gauge set simply called the "electronic control module". I don't recall seeing any regulator but I will dismantle it again when I have a chance and have a look (needed to put it back together so the missus could drive it).

The fuel sender is resistance based in the NB.

It would be very much appreciated if you could scan the relevant pages of the XF tech training bulletin for me as it might help me sort it out. Thanks"

PS the fuel gauge which is in the same assembly as the temp gauge works fine as does the tacho and digital speedo.

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On Sat, 07 Mar 2009 23:00:49 GMT, "aussiblu" put finger to keyboard and composed:

The gauge incorporates a trimpot. Maybe its wiper is intermittent?

Anyway, here is a scan of the relevant pages:

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- Franc Zabkar

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On Sun, 08 Mar 2009 10:28:56 +1100, Franc Zabkar put finger to keyboard and composed:

Here is another diagram of a water temperature gauge:

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I'd measure the resistances between the V+ terminal and the ground and sender terminals.

- Franc Zabkar

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Thanks for those scans Frank. While the fuel gauge has a trimpot the temperature gauge doesn't.. I've replaced and repaired the fuel sender before and its the old fashioned resistance based wiping pot type. The pics you sent I think shows the 68 ohm resistor where the 88R labelled item is. - it might just be a badly printed "68" that looks like a "88" but the one on the fuel gauge reads 90 ohms while the one on the temp gauge reads 57 ohms. In any event I will look for a tenor diode as well now.

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Thanks again Frank

Re: '' I'd measure the resistances between the V+ terminal and the ground and sender terminals." I've done that and essentially confirmed that the problem is in gauge somewhere. I guess if I remove and replace the resistors and any zener diode that's as much as I can try. I hope if there is a zener it's labelled.

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I hope I can get this working as my problem if I can get a new gauge from Ford or ebay will be which one do I need. I have a parts manual on CD that shows five different part numbers that vary by production date. I have already confirmed some years ago when the gauge was working correctly that the gauge set in there isn't the one prior to 9/89 (although the car was made in

8/89) which used a different sender (midrange on the gauge for the earlier one was 56 ohms) .

There are no numbers on gauge set that match part numbers but the whole cluster is labelled in black felt pen on the white plastic surround something like "MV-1 Test Inst 68K" which I assume suggests it was a prototype or new type instrument cluster fitted at 68 km or perhaps even 68,000 km. I will 1st be trying the one that goes from 9/89 to 6/91 although Ford New Products Engineering owned the car to 1992 so it could also be the 6/91 to 2/92 set or even the 2/92 onwards set. Most things on the car including the even original plastic centre caps on the mags are labelled in beige paint or black felt pen "MV-1".

The joys of owning an ex prototype. Though with luck Titan Ford's parts guys might find an NB annotation on their online parts catalogue as they occasionally have.

The car is essentially mostly a mix of NA and NC Fairlane parts with a few bits from other model Oz and US models thrown in. The original ECU computer (since died and replaced by me) in self diagnostics mode identified it as a 6 cylinder Thunderbird so I suspect the multipoint Electronic Fuel Injections was a modified version of that on the 6 cylinder T bird and they just copied and modified the ROM software in the ECU. It appears at one time it had front as well as rear self levelling suspension (disconnected air lines were still in place running to the top of the front shockies). The only other odds parts that as I can remember that aren't NA or NC parts have been tie rods ends, bypass hose, and some of the auto gearbox internals (some solenoids in vertical rather than horizontal positions - it appears to be the first 4 speed auto fitted to an oz made Ford). When I had to rebuild the motor I also found that although the head was stamped 3.9 L, the engine bearings and the crankshaft were different and it apparently was stroked by Ford from 3.9 L to 4 L. Luckily ACL also knew about it and had several sets of bearings to fit. In fact many aftermarket makers recognise and list NB parts (some even list an NB II suggesting there might be another although more likely the just assumed there was an NB model equivalent to the EB Series II Falcon). However, Ford refuse to acknowledge the model exists.

According to Ford despite what's on the compliance plate, I simply have a mislabelled NA (they have even offered to change the compliance plate for me - an offer I politely declined) . It might be because when I asked DOTARS (who issue compliance plates) that Department advised that it was illegal plate had never been authorised by them for use on a production vehicle for sale to the public. I also chased up its rego history and it was always registered as an NB model by Ford. Ford do acknowledge the car is one of their ex prototypes and say hat it should have been scrapped rather than sold. There are two reason why it might have been sold: a) it appears to have been abandoned at a Ford dealer in Geraldton while on an around OZ test drive and the dealer simply got tired of it taking up space (the evidence is it blew a head gaskets that was replaced just before it was sold but it also has 1992 upholstery and carpets fitted so perhaps it got caught in a flood or something) and b) it was sold at the when Ford were claiming they were at risk of closing the OZ operations and they were selling off all sorts of surplus assets.

Titan Ford parts staff have been very supportive though. They have taken an interest in the car and been very helpful in ID ing parts as required. As far as they can ascertain my car is also the only NB, or mislabelled NA, that escaped into the public domain.

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On Sun, 08 Mar 2009 04:31:31 GMT, "aussiblu" put finger to keyboard and composed:

MV = Motor Vehicle ????

68K = Motorola 68000 CPU ???

Is this the EEC-IV ECU? If so, I have lots of info on this box, including my own reverse engineered hardware info. There is also a US forum that has reverse engineered the firmware.

- Franc Zabkar

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Re "Is this the EEC-IV ECU? If so, I have lots of info on this box, including my own reverse engineered hardware info. There is also a US forum that has reverse engineered the firmware."

Yes and I also subscribe to the EECTuner Forum Digest etc but my time constraints due to work and family commitments no longer allow me to play as once I would (pre children). Unfortunately the reason I had to replace this ECU was a corrupted ROM so that unique bit of history is probably lost forever.

"MV-1" is written in beige paint or black texta on virtually everything on the car including even the inside of the plastic hubcaps on the mag wheels. Other frequently cryptic notes, numbers and dates sometimes accompany it. I suspect "MV-1" stands for "Motor Vehicle 1" referring either to the 1st (and as it turns out probably the last) NB model or the first Oz ford fitted with a BTR 4 speed automatic.

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And I guess you have these sites bookmarked:

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and this

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and

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On Mon, 09 Mar 2009 02:17:42 GMT, "aussiblu" put finger to keyboard and composed:

I'm not a Ford fan, but I had a bunch of EEC-IV boxes to look at many years ago. I anticipated continuing work, so I invested some time in getting to know the product.

- Franc Zabkar

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PS it's the zener and I am patiently waiting for RS Components to mail me some suitable replacements I have ordered. While 4 of the 6 cars in this household that I look after are Fords I'm not sure if I am a Ford fan either. It's just that they are generally cheaper than Holdens (I do have and EH Van I inherited from my father as well) and I have built an inventory of special tools and knowledge on how Fords work or more to the point sometimes don't work so I am encouraged to stay with the known technology. Thanks again for your help.

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