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how strict are Temp II's spec resistances?
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Bambus
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PostPosted: Sat Jun 23, 2007 7:31 pm    Post subject: how strict are Temp II's spec resistances? Reply with quote

Yo asylum: the silver bus runs again! New pressure regulator got it sorted (well i imagine the new batt made a huge diff too, digress...)(more digression: it's night right now and a few mins ago i had it idling and turned all my shop lights off and watched into the inky black motor room to see if i could see leaking sparks-- shonuff: there was a consistent spark where the coil lead passes over the hoseclamp of the large topside hose. Was also sparking where #3's lead was making the *slightest* contact with the woven ground strap. Fascinating-- i'll be doing some slight re-routing of the new wireset to keep from passing over possible grounds)

Anyway, just tested Temp II and need to know how specific to regard it's operating-temp resistance vs spec values. After idling the bus long enough for the fan to go through stage 1 and then 2 briefly, i took Temp II's temperature w/ a laser thermometer: at 80C i read a R of 220 Ohms across the terminals. I looked up the values in the Temp II graph in Bentley-- at that 80C temp, manual says i should be seeing apprx 290-380 Ohms. So mine is some 70 Ohms south of minimum spec. Is that variance enough to matter?

BTW: stone-cold values were similarly low (about 1050 Ohms at 20C) vs spec--

The hot variance from spec does'nt seem like a huge gap-- thoughts?
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Randy in Maine
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PostPosted: Sat Jun 23, 2007 7:48 pm    Post subject: Reply with quote

Try it without using a laser thermometer. Not suitable for what you are trying to do.
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Lanval
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PostPosted: Sat Jun 23, 2007 10:27 pm    Post subject: Reply with quote

Randy,

out of curiosity, are you saying that the laser thermometer is insufficiently accurate for the procedure? I know mine claims a +/- of 4 degrees or 2%, which would seem pretty accurate for most engine diagnostics, but now I'm wondering if that's not always the case...?

Thanks for your enlightenment,

Lanval
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Randy in Maine
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PostPosted: Sun Jun 24, 2007 4:21 am    Post subject: Reply with quote

I say no.

If you are an air cooler, I know that beeping the area by the #3 cyclinder head does not give you an accurate reading for what the temp of the TS II is let alone the CHT.

If you are pumping water, verify your reading with another means to measure temperature and see what you get.
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Bambus
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PostPosted: Sun Jun 24, 2007 9:43 am    Post subject: Reply with quote

the point about verifying measurement instruments against others is valid, but the main thrust of my question has been bypassed here.

For argument's sake let's say i repeat my tests w/ a hot engine and a mercury thermometer and get the same results (see above-- my Temp II resistance at 80C (176F) was some 70 Ohm below the minimum specified in the relevant Bentley graph (p 24.32 in mine))

So the original question is still open: is the variance i'm seeing too small to matter?
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Dogpilot
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PostPosted: Sun Jun 24, 2007 12:46 pm    Post subject: Reply with quote

There is some misconception about the Temp II. It works with the ECU more like a set point. When the engine gets to a pre-determined temp it goes to normal running mixture control. If your resistance is off (the variation allowance gets much smaller the higher the temp), then the point where your ECU goes from warmup to normal may vary making your engine run too rich, or poorly for a while until it heats up. In some of the literature it is referred to the "Thermotime Switch".

They are a very cheap part, like under $20 with shipping and available from most auto parts outlets. If it varies, replace the stupid thing. If you want to be empirical, put it in boiling water with an accurate thermometer and check it that way. A couple of degree at boiling makes quite a resistance difference.

The thermistor that makes a difference in normal mode is the one in the AFM. The ECU varies its program due to outside air temp (air density) as read in the AFM.
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Bambus
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PostPosted: Sun Jun 24, 2007 10:30 pm    Post subject: Reply with quote

Dogpilot wrote:
They are a very cheap part, like under $20 with shipping and available from most auto parts outlets. If it varies, replace the stupid thing. If you want to be empirical, put it in boiling water with an accurate thermometer and check it that way. A couple of degree at boiling makes quite a resistance difference.


true enough on these pts, Dog. These resonably-priced individual parts add up though, when one is into the resurrection ops. You know how it works: you start into refreshing a previously neglected van, and the "may as well do that too" shopping list grows beyond pocket-money.
PLUS-- i've compiled the sass to use a meter and published data, i'd like to employ that as a hedge against "well this part is pretty cheap, go ahead." I'm anal, and i like to measure (fire for effect with the puns, lads)

You have given me a nudge toward answering my own question, though, which is always rewarding: when Temp II resistance is high (cold engine) = "send more fuel for enrichment, please." When op temp is high (warmed/hot motor), resistance at Temp II lowers considerably = "no more enrichment fuel needed here." My Temp II is reading _lower_ resistance than pub'd data when hot, so i can now place a guess that my hot Temp II is not asking for more gas when warmed/hot. If my resistance readings when hot were *higher* than spec, then i could logically expect a rich condition. My call is Temp II is off the suspect list.

Thanks for loaning me a crutch up the wbx learning curve.
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Dogpilot
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PostPosted: Sun Jun 24, 2007 11:09 pm    Post subject: Reply with quote

Oh I defiantly see the throwing parts at it monetary bit. My son pointed out, while we were driving out to the airport in the Van today. "Dad, wouldn't it have been easier to have just started with a shell of the van and built it up with new parts, rather than replacing them one at a time."

Wisdom from the mouth of babes.
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98 Disco I
08 Range Rover SC
08 VW Rabbit S
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Bambus
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PostPosted: Sun Jun 24, 2007 11:23 pm    Post subject: Reply with quote

Dogpilot wrote:
"Dad, wouldn't it have been easier to have just started with a shell of the van and built it up with new parts, rather than replacing them one at a time."

Wisdom from the mouth of babes.


pray tell how you answered that insightful/leading-the-witness question!
(and is not the result the same anyway? Seems that way with the ones i've had. By the time they're mech bullet-proof the rust that i've ignored for years starts looking at me...)


MRP
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