Ohm's on a WUR 090

[joe912/62]

What ohm reading should I be getting on 090 WUR? Can't find it on my Bentley service manual. It an 82 SC

[Dpmulvan]

33 ohm.

[boyt911sc]

Originally Posted by Dpmulvan

33 ohm.

Much lower than 33 Ohms.

Tony

[joe912/62]

I get 26.9 ohms. Would that be correct?

['78 SC]

It depends on the temperature...

The 090 WUR has two resistance heaters, a primary heater with 26 ohm resistance and a secondary 16 ohm heater. There is an internal switch operated by a bimetal strip (not the same one that affects the control pressure pressure) that closes around 50F to activate the secondary heater. The two resistance heaters are wired in parallel, so their combined resistance is about 10 ohms. So at room temperature the resistance should be about 10 ohms.


Details per the great Jim Williams here.

[Dpmulvan]

Originally Posted by boyt911sc

Much lower than 33 Ohms.

Tony

I got 33 ohm out of the factory workshop manuals, sorry didn’t mean to give out bad info.

[boyt911sc]

Originally Posted by '78 SC

It depends on the temperature...

The 090 WUR has two resistance heaters, a primary heater with 26 ohm resistance and a secondary 16 ohm heater. There is an internal switch operated by a bimetal strip (not the same one that affects the control pressure pressure) that closes around 50F to activate the secondary heater. The two resistance heaters are wired in parallel, so their combined resistance is about 10 ohms. So at room temperature the resistance should be about 10 ohms.


Details per the great Jim Williams here.

‘78 SC,

Jim Williams did a very good job making a data base for CIS. But it has some flawed section/s and nobody seemed to notice it. And the misinformation is carried over the years until his retirement.

The switching temp. @ 50°F is not even near the actual switching temperature. And at room temp., a reading of 10 Ohms means the WUR is out specification. And the motor will always have erratic cold idle.

This is not a typo. If you have 10 Ohms reading at room temp. for WUR-072/-090, the WUR is out spec. I have hundred of hours of tests and actual rebuilding experience to contradict the above myth.

I will be 80 years old next week and healthy. But don’t want to keep this trade secret to my grave. I have enough work to keep me busy for a long time. The least I could do, is share some critical information to keep CIS troubleshooters on the right direction. Keeping my silence and allowing the myth to perpetuate is unforgivable.

Tony

[AndrewCologne]

'78 is correct regarding the two resistance heaters on a -090 WUR. On a -090 WUR : with cold ambient temp you get a 10 ohms reading and above this will be 26-32 ohms.

EDIT: Did read '78 post too fast ... with cold ambient temp 26-32 ohms reading and non cold ambient temp 10 ohms

[boyt911sc]

Originally Posted by AndrewCologne

'78 is correct regarding the two resistance heaters on a -090 WUR. On a -090 WUR I have the specs: with cold ambient temp you get a 10 ohms reading and above this will be 26-32 ohms.

Andrew,

You are not the only expert in CIS that believes in this 10-Ohms at room temp. myth and that’s the reason I have so many people sending their WUR’s to me to be fixed. The two (2) heaters at RT are 26 and 16 Ohms and the resulting resistance with the switch closed is 10 Ohms.

The switch should not be closed at 50°F and give you a 10 Ohms reading. Have you rebuilt a WUR-072/-090? I have done over a hundreds of these WUR’s and counting for fellow Pelicanparts members with amazing success. BTW, I have a specially built instrument by someone (mechanical, electrical, and instrumentation engineer) and a successful scientist to monitor the actual switching temp. The result is very accurate and reproducible. And the transition temp. is not 50°F.

Tony

[boyt911sc]

Originally Posted by AndrewCologne

'78 is correct regarding the two resistance heaters on a -090 WUR. On a -090 WUR I have the specs: with cold ambient temp you get a 10 ohms reading and above this will be 26-32 ohms.

Andrew,

You got your spec totally wrong. I will give you the benefit of the doubt that you are correct for the sake discussion:

• When the engine is cold and you have 10-Ohms reading, the switch has already closed.
• No amount of heating could close the switch because it is already closed. Heat will only close the switch more.
• So additional heat no matter how long will not change the 10 Ohms to increase to 26 Ohms. NEVER.
• For it to register to 26 Ohms, the switch has to open. The switch needs to cool down. This is where your understanding is flawed.

I could give you more facts about WUR-072/-090, but if you don’t understand the above information, there is no point to continue this discussion because you have no idea how the system works. BTW, your WUR is out spec and needs some work.

Tony

[ahh911]

There was one poster with a brand new old stock 090 wur, he monitored the crossover from 26 to 10 Ohms and it was above 10C/50F, can't find the post and it's only one data point. Anyhow, I set my 090 to ~20 DegC, 68F, but in my notes there is an entry that mentions increasing the cross over point to 30C, 85F. I don't think I bothered increasing it because the drive off at all temperatures (-41F to 90F, -5C to 85C cold starts) is "perfect" right after start, or if you let it idle it's very sweet in terms of rpm, smell etc..



Phil

[AndrewCologne]

Originally Posted by boyt911sc

Andrew,

You are not the only expert in CIS that believes in this 10-Ohms at room temp. myth and that’s the reason I have so many people sending their WUR’s to me to be fixed. The two (2) heaters at RT are 26 and 16 Ohms and the resulting resistance with the switch closed is 10 Ohms.

The switch should not be closed at 50°F and give you a 10 Ohms reading. Have you rebuilt a WUR-072/-090? I have done over a hundreds of these WUR’s and counting for fellow Pelicanparts members with amazing success. BTW, I have a specially built instrument by someone (mechanical, electrical, and instrumentation engineer) and a successful scientist to monitor the actual switching temp. The result is very accurate and reproducible. And the transition temp. is not 50°F.

Tony

Hi Tony,

thanks for your kind words.
a) I mixed up the cold/warm states and their ohm values in my post above, so here keep cool! That simply happens.
b) Yes I did rebuild WURs, dont know why you directly are in doubt (maybe cause of my written typo means mixed up warm/cold states, but still no reason to be in doubt in such a way), And you dont need to count your rebuilds to me to proof your experience, as -honestly- Im not the one in doubt here with your knowledge.
c) I did nowhere mention that 50°F value in my posts, just cold and warm, so no specific values named from my side

You got your spec totally wrong. I will give you the benefit of the doubt that you are correct for the sake discussion:

When the engine is cold and you have 10-Ohms reading, the switch has already closed.
No amount of heating could close the switch because it is already closed. Heat will only close the switch more.
So additional heat no matter how long will not change the 10 Ohms to increase to 26 Ohms. NEVER.
For it to register to 26 Ohms, the switch has to open. The switch needs to cool down. This is where your understanding is flawed.

I could give you more facts about WUR-072/-090, but if you don’t understand the above information, there is no point to continue this discussion because you have no idea how the system works. BTW, your WUR is out spec and needs some work.

Thanks for your additional post and and thanks again for the direct speech or better said for that kind (of) response. See the explaining above where I "mixed up" the states of the WUR at warm cold – period.
So my WUR works fawlessly with a correct non irratic idle at cold and warm ambient temps as it corresponds to the specs you mention further above.

And my understanding is not "flawed" and I have the idea how the system works, thanks for pointing me to your doubt in such a way you do above. Here a misunderdstandiung based on a typo was the case, so no need for such a repmirand! If you would know me, you would react different and not with such a presumtion regarding my knowledge.


Cheers from Cologne and .... have a beer

[boyt911sc]

Originally Posted by AndrewCologne

'78 is correct regarding the two resistance heaters on a -090 WUR. On a -090 WUR : with cold ambient temp you get a 10 ohms reading and above this will be 26-32 ohms.

EDIT: Did read '78 post too fast ... with cold ambient temp 26-32 ohms reading and non cold ambient temp 10 ohms

Andrew,

If there is someone in this community that knows CIS very well, it would be you. And I follow your posts with much interest because I could learn something from them. It was a total surprise to me when I read your above post. It was something I never expected to come from you. I have a very high expectation for your knowledge and experience.

I made a lot of mistakes too. But what impresses me most is your willingness to admit committing a mistake. It takes courage and determination to acknowledge making a mistake.

I take off my hat and bow my head to you. You are a gentleman and a scholar.

Tony

[AndrewCologne]

Hi Tony,

all ok! Thanks for your last post and clearification.

And all the best!

[ahh911]

Originally Posted by AndrewCologne

Cheers from Cologne and .... have a beer

Maybe too many beers going around to begin with

Tony I guess at 80, five beers is the limit?

[boyt911sc]

Originally Posted by ahh911

Maybe too many beers going around to begin with

Tony I guess at 80, five beers is the limit?

Phil,

When I was in college 60 years ago, I could only drink 3 bottles of beer (San Miguel). I could not remember the 4th bottle went anymore. Today, even the wedding champagne drinks make me drowsy already. So no more alcohol intake for me.

Tony

[Charles Freeborn]

I've got a '74 with WUR 0 438 140 008. It is the non-vacuum model, which I understand is non-rebuildable. I have no interest in buying another one as I plan to go MFI with a rebuild next winter.
So, 2 part question:
Correct Ohms, cold, hot or otherwise?
Can I throw the stupid thing in the trash and somehow convert it to manual, as in an old fashioned choke lever. I have an AFR gauge, so I can pretty easily monitor the warm up mixture.
Thx.

[PeteKz]

A choke would not work, but you could rig up a valve that bleeds off control pressure along with a gauge that you can see and operate from inside the car. It would have to act like the WUR. As the car warms up, you will need to increase the control pressure. The bonus is that you can fine tune the mixture on the fly, to get either max power at WOT or max economy at cruise.

[Charles Freeborn]

This is the idea I've got in mind. Doesn't need to be operable from inside the car. I don't mind standing at the engine compartment as it warms up and adjust until it's warm enough to drive.

[PeteKz]

Charles, you won't be able to put much load on the engine standing behind it. At some point you will want to put the adjustment valve where you can reach it while driving, and see the resulting AFR.