Purple ring temperature sensor

Post by **jkxr4ti** » Wed Jul 25, 2007 12:23 pm

Ford has used the same temperature sensor on many domestics for years. I looked on advanced auto 's website and the same sensor is listed for:

87 tempo 2.3
87 mustang 5.0
87 mustang 2.3
87 t-bird 5.0
95 mustang
96 mustang

All are delco part # F1855

Should I go on?

If your sensor is from an 87 tempo add the 33 ohm resistor in series and drive.

Good Luck

xr4man · Post by **xr4man** » Wed Jul 25, 2007 7:17 pm

yeah i already tried a sender from a 87 tempo. it doesn't move the gauge at all let alone read high. so adding in a 34 ohm resistor to it doesn't do snot. it just sits at the bottom of the gauge. the gauge operates at 19 ohms on the hot side and 240 ohms on the cold side. when i check the resistance of the sender at approximately 210* (which is when my fans kick on) i am reading 200k ohms. it doesn't even start to get to the point where the gauge can begin reading it. i measured the resistance from the center conductor to the base of the sender then to the upper intake then to the round on the upper intake then to a nice ground on the fender. all spots read the same resistance so it's not a ground problem.

we'll see what happens with the cossie sender in a few days.

xr4man · Post by **xr4man** » Tue Aug 14, 2007 9:37 am

ok, so i installed my brand new cosworth temp sender last night. it worked and it didn't. the temp gauge actually moves now, but still reads really low. i got it up to temperature this morning and tooka resistance check on the sender and i was reading 135 ohms. which is right between the 19-240 ohm range. so i think now there may be a problem with my gauge even though it tested ok according to the manual. so, i believe that the cosworth sender will work perfect once i get the gauge sorted. and with shipping it came to a grand total of $11.60. the cosworth sender is a smaller diameter,but a $1.50 for an adapter at home depot took care of that.

Post by **Ed Lijewski** » Tue Aug 14, 2007 12:16 pm

Remind us where you got the Coswroth temp sender, please.

YMMV

Post by **jkxr4ti** » Tue Aug 14, 2007 12:39 pm

I really wish we could get a side by side comparison of the temp vs. resistance values of both the purple ring sensor and a standard ford unit. If this happens we can make a proper determination of exactly which thermistor is in each case and come up with a solution. Maybe this has already been done and its in the IMON archives somewhere.

I can tell you that with the mustang sensor listed above and the 33 ohm resistor my gauge operates in the normal ranges that you would expect. Fan comes on at approximately gauge position 3:00 and off at around 3:30.

xr4man · Post by **xr4man** » Tue Aug 14, 2007 12:55 pm

Ed Lijewski wrote:Remind us where you got the Coswroth temp sender, please.

YMMV

sure ed,

it's part number yb0201 from .....

cosworth.

xr4man · Post by **xr4man** » Tue Aug 14, 2007 1:32 pm

jkxr4ti wrote:I really wish we could get a side by side comparison of the temp vs. resistance values of both the purple ring sensor and a standard ford unit. If this happens we can make a proper determination of exactly which thermistor is in each case and come up with a solution. Maybe this has already been done and its in the IMON archives somewhere.

I can tell you that with the mustang sensor listed above and the 33 ohm resistor my gauge operates in the normal ranges that you would expect. Fan comes on at approximately gauge position 3:00 and off at around 3:30.

the gauge operates between 240 ohms and 19 ohms. what i don't under stand is how can you get a mustang sender and add in 34 ohms in parallel and it work right.

i guess if it operated at 0 ohms on the hot side then it could conceivably put the gauge right in the middle with a 34 ohm resistor, but the gauge would never be able to read overheating. the hottest the sender would let the gauge read would be whatever teh 34 ohm reading is. it would never get to 19 ohms.

Post by **jkxr4ti** » Tue Aug 14, 2007 4:47 pm

FYI the resistor is in series with the mustang sender so i would assume that the purple ring sensor is of a lower resistance value than the mustang unit. Ive got several NTC thermistor curves and data sheets on my desk. I'll take a few readings of the mustang unit tonight and see what it matches up to. Then all i need is the values from the purple ring sensor to give you the whole story.

xr4man · Post by **xr4man** » Tue Aug 14, 2007 7:43 pm

forget that mustang sender. i have the solution.

ok, so some of you have been following this for a couple weeks. i finally got my cosworth temperature sender. i installed it last night and still it was reading low. this morning i got to work and left the car running. i got a multimeter and came back out and disconnected the temp sender. then i took a resistance check. i read 134 ohms, which should be just right for a mid gauge reading, so it looked like the sender was working. i just got home and swapped out the gauge for the one from my black 88 and suddenly it worked.

so, it looks like the cosworth sender is a proper replacement for the xr's.

the part number is yb0201. you can get them new from cosworth. the total price with shipping was $11.60.

the only thing i had to do was get an adapter because the cossie sender is much smaller than the xr's. then cut the connector off the wire and crimp on a female spade connector.

works like a champ now.

hope this helps some of you who want to keep the interior stock.

xr4man · Post by **xr4man** » Sun Sep 09, 2007 3:55 pm

i just got back from some real world testing and here are the results.

under normal cruising the temp gauge reads about half way between the mid-range and the second cold hash mark. when sitting at a light it gets to the mid way point and my fans come on.

this is good enough for me, so i am declaring using the cosworth sending unit a success for my purposes.

Post by **jkxr4ti** » Tue Sep 11, 2007 10:06 pm

XR4man I agree with you on the point you mentioned above with the sensor having to go to zero to bring the gauge to the top of the range so i checked it the other night. With the 33 ohm resistor in series with the gauge lead and the other side grounded the gauge reads just shy of the top of the normal range. I think i'm going to order the cossie unit and do some side by side resistance tests. I have a K type thermometer here so i can get some pretty accurate comparisons of resistance at a given temperature.

If the cossie unit is really the purple ring sensor in a different package lets get this moved to the FAQ section once we get the details down.

Anyone else have any more info on this?

Post by **DPDISXR4Ti** » Fri Sep 14, 2007 1:54 pm

I may have some interesting news to add to this thread. I took a junkyard detour yesterday and found my head under a early 90's Escort with the 1.9L SPI motor. First, I notice a dual-bung 3/8" NPT in-line fitting on the coolant line to the heater core. Conveniently, the in/outlets are 5/8" rather than the 3/4" fittings we often grab from Mustangs, Rangers, etc, and then stretch out our 5/8" hose to fit.

So I get after it, cutting the hoses off, since there's a semi-permanent band fitting that secures the hose (which I'll cut off later). As I'm doing that, I notice the gauge sender a little closer - and I notice that the insulater ring is PURPLE!

At an ambient temp of about 70 degrees, I'm getting a reading of about 3.25 Ohms. Does anyone have a comparable data-point from "the XR spec" purple ring sender? Obviously, I'm wondering if indeed they are the same part!

Post by **Ed Lijewski** » Fri Sep 14, 2007 2:15 pm

I took and posted readings from a spare used purple ring sensor and a new one (from OPMD) several months or a year ago. Could be I posted them here and on IMON. But I typically find only a portion of things I'm looking for using the Search function here, so...be my guest; your skill or luck may be better.

YMMV

Post by **DPDISXR4Ti** » Fri Sep 14, 2007 2:32 pm

Found it...

http://forum.merkurclub.com/forum/viewt ... urple+ring

Looks like it should be 4-500 Ohms at room temp - so much for thinking the Escort sender might work...

Post by **Ed Lijewski** » Tue Jun 10, 2008 4:58 pm

Well, maybe we need to look at that Escort "purple ring" temp sender again.

Here's why: Last Friday, prior to leaving for Carlisle, I decided to install that new temp sender I noted I bought earlier from OPMD, as the one in the car I would drive seemed to be reading lower than I thought it should given the recent heat wave. Turned out that the "new" one, with the engine at normal operating temp under idle (and in the shade) read over 2/3rds of the way to the upper limit; and during operation under typical but light traffic tended to increase slightly more to the upper register. The radiator in this XR is a double pass with few thousand miles on it, engine is full rebuild, water pump is new, etc. so overheating wasn't likely. I confirmed that with readings from a digital pyrometer that showed temp rises to around 205+ before the fan kicked on and ~190 by the time it kicked off.

So, I removed the "new" one and reinstalled the prior one (which I still believe is reading low but which I felt more comfortable using on this trip, given the pyrometer readings above).

Bottom line: the test readings I took on the "new" one at ambient temp, mid-temp and in boiling water (see post above) aren't what a true "purple ring" sender should provide; and therefore, looking further into trying a sender from one of the Escorts that used it in XRs is indicated.

So, Brad, can you pin down a bit more what year Escort you got that temp sender unit from? Wiipedia doesn't identify Escort engines as you did above: http://en.wikipedia.org/wiki/Ford_Escor ... #Engines_3

YMMV