Temp Gauge Sender

XR4Ti / Sierra / Sierra Cosworth Discussions - Questions, problem resolution, general talk, technical tips and modifications.
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Dan B
Posts: 1
Joined: Wed Jan 26, 2022 4:02 pm

Temp Gauge Sender

Post by Dan B »

The temp gauge reads consistently high in my 89 XR. The car doesn't seem to behave like it is running hot, but I would be more comfortable if were closer to an acceptable reading. Are there any of those unicorn purple ring senders out there? I also remember seeing a table of 'resistance ratings' to 'indicated temperature' somewhere in the wide selection of manuals and documentation, but damned if I can find it now! Help me find that info and I'll try to come up with an available sender that is easier to come by...

Thanks in advance!
Dan Boehm
Posts: 24
Joined: Mon Aug 21, 2023 6:24 pm

Re: Temp Gauge Sender

Post by Chesterfield »

Joshua Lawrence wrote:· Purple Ring Sender alternative and Anti Slosh board by , Joshua Lawrence
I have a possible solution to both problems mentioned. If anyone knows this to be a bad idea,
please chime in. First is to bypass the slosh board. This was discussed on the old list quite a lot.
If you are having intermittent readings on your gas gauge, or if it reads full at all times, this is
most likely your problem. Bypassing is very simple, basically you will wind up unplugging the
board, and removing a nylon spacer to bypass it. It is a quick and painless process. There was
some discussion a long time ago about this board's purpose, the most common opinion was that
it simply prevented fluctuations in the gauge. The other was that somehow it might decrease the
power sent to the in tank sender (if I understood it properly); however nobody ever came up with
any evidence for this as far as I know. I do know however, that after bypassing it, the gauge does
fluctuate more, but certainly not an unreasonable amount. Mainly it is noticeable when going
on/off ramps, you will see it drop. Anyway, if anyone needs more info about the exact process, I
can give a stepbystep,
but it should be found in the archives somewhere I would think. Now, the
second half has to do with the aftermarket replacement senders. The problem with these is that
once installed they cause the temp gauge to read high. Based on the chart provided to us a short
time back, I attempted to recreate the test using my aftermarket sender. Unfortunately, as near as
I could tell the difference in resistance between the two units was very small. Even worse, it didn't
appear to be "linear" as such, the difference at given temps would fluctuate anywhere from 210
ohms. I made a complete chart, but the information seemed to be pretty much worthless.
Anyway, what I wound up doing, is installing a 15 ohm resistor up at the instrument cluster
instead. Basically, I placed this at the last stud on the cluster (furthest to the passenger's side). I
originally installed a rheostat inline and started at a value of "0", then continued to increase
resistance until the gauge was in the center of the gauge with the engine fully warmed. The actual
value I came up with was 18 ohms, however Radio Shack only had 15 & 22, so I went with the
lower as I would rather it read a little higher than low. I used the nylon spacer from the slosh
board to install this resistor; basically I crimped eyelets on both ends, then placed them on either
side of the nylon spacer around the terminal. I have had this setup for a couple weeks now, and it
appears to work very well. Just above the center of the gauge, the fan kicks on, and kicks back
off right about in the middle. Just to clarify, the point of doing this is so you will be able to use any
aftermarket sender rather than the "purple ring" model. First of all, the generic model is only like
$12, and secondly the proper model is getting hard to find from what I understand. So.....if
anyone has any input on this, I would be interested to hear it; but so far so good! Oh yes, I did
take pictures along the way, and could do a complete guide for the process if someone would
want it. The entire process should take around half and hour I would think. Thanks, Joshua

FYI Joshua Wanted 18 ohms. R3 (18 ohms) = R1 * R2 / R1 + R2. so a 45 ohm and a 30 ohm (in parallel) will give you 18 if you just want to try it.
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Re: Temp Gauge Sender

Post by zxr250cc »

Hi all,

Is the cooling system clean? It has been flushed with a good cleaner, rinsed out and then filled with 50/50 coolant and water? These motors have some quirks and trying to have a build up of crud in the cooling channels is one of the quirks. In mine it seemed OK but not totally good so I drained the system, filled it with vinegar and went for a fifty to sixty mile drive. Pickled Merk anyone? LOL

It cleared things out and all has been good. Mine sat for a long time so it might have been more likely to have an issue than yours. Prestone and others make good radiator and system cleaners. Motorcraft cooling system cleaner is very good and I have used that in a Taurus with good results over the years.

If a car has sat a long time the coolant needs changing as much as the oil, differential gear oil, ATF transmission fluid or transmission gear oil. By design the chemicals in antifreeze are used up and depleted to keep things from corroding or rusting.

Just a thought and vinegar is very cheap.

1986 XR4Ti Mineral Blue Metallic
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