jaredb3000

Greetings all,

Recently got into a nice 85 4runner 22re- will update pics/account shortly. Being the novice I am at trouble shooting electrical stuff, I've first mulled over this forum and T4R as well, trying to figure out the cause of an erratic temp gauge -usually the needle is sitting at 50% (even when cold) with an occasional flutter to 0%, and even more rare visit to 35-40% which I suspect is an actual reading.

Based on what I've found mostly here at yotatech, I've since pulled out the gauge cluster and cleaned up (lightly with an eraser) the brass rings at the terminals on the back of the gauge cluster (fastened with brass screws that contact the circuits) and gently cleaned up the wiring harness contacts- same deal with the 50% with key at ACC.

With a multimeter at the Ohm 200 setting, I tested the 3 terminals with the key at ACC position and received the following reading:

IG-TU: reading of 70.5 - should be 135 (per the service manual)
TU-E: reading of 74.3 - should be 138 (per the service manual)
IG-E: reading of 5.4 - should be 273 (per the service manual)

These readings were with the meter touching the screws themselves, if I touch the brass contact area the number would jump around, usually to a much higher number.

I was a little unclear how to get a proper reading from the temp sender (at the thermostat housing), and then noticed that the gauge remains at 50% with or without the the connector fastened to the sender, so I've ruled that out for the moment.

Having looked at numerous threads (where opinions vary drastically) the 85 22re sending unit is a one prong unit, of which there is only one sender and not 2 like on later 22re models (so says the service manual and a few folks' threads...)

If anyone can help narrow it down based on my ramble, and/or walk me through how to test for which wire has issues if I've exhausted the likely culprits (again- I'm a novice with electrical but its starting to make sense) I would really appreciate it.

As there is no such thing as dumb question - for resistance testing does it matter whether the key is in ACC, ON, or actually fired up to affect the reading?

Lastly- in disconnecting the negative battery terminal to install a stereo and then work on the temp gauge, I've come to find that the bolt holding the contact to the neg batter terminal ismovable, and as such, although snug, the connection is by no means tight (its apparently been held on by tension, and can easily be removed and placed back on). The present connector that needs replaced is stout, and soft making me think its lead- the replacement connector I've yet to replace is "lead free" (recommended by autozone...), and much skinnier (stainless probably, though its not in front of me at the moment); question 1: although there is no other electrical issues, could this alone be the culprit? Q2: is it OK to replace the current lead connector with a non-lead one?

Thanks much-

JB

EFI85

man i tried everything i ended up with a manual gauge .. Sorry i cant help ya if you get it figured out please let us know id love to have both working in my truck

CajunKenny

JB: Very thorough explanation and effort! There are a lot of threads where folks don't try anything prior to posting. Good job!

When I first purchased my 87, the temp gauge did exactly as yours. I am an Electronics Technician so I confidently started in on the problem. I'll spare you all the details of the troubleshooting and cut right to the chase...

If you remove the gauge cluster and disassemble it, you'll find a 1 Watt Resistor behind the temp gauge assembly. In my case, that resistor had heated up to such a degree that it caused the solder to break. Aka: Broken Solder joint.

I desoldered the resistor and removed the 20+ year old solder and then reinstalled the resistor. That was the fix for mine.

Special care must be taken when disassembling the gauge cluster. There are very small components that can easily be damaged. VERY easily damaged!!!!!

If you or anyone that attempts this repair isn't completely confident in their abilities, then find someone who is.

And of course...this may or may not be your problem. *DISCLAIMER*

jaredb3000

EFI 85- I'll definitely let you know what I come up with. Need to get this sorted before I can take a longer trip to the mountains this spring, and break in the soft top that arrived last night...

CK- thanks much for the info! I've done a decent amount of soldering wires in guitars to replace volume knobs, jacks, and pickups over the years, do you think that I would need more finite skills than this? Would a standard soldering iron and some tweezers cut the mustard? If there is anything too close by this resistor that I could damage with heat, perhaps I'll find an electrical tech in town who wont gouge me...

Someone at T4R forum suggested that if I pull the wire off of the sender and still get a resistance reading from the wire, it would probably be a corroded wire- do you think that both of these possibilities could be the culprit if I get a resistance reading? I like the sounds of a visual inspection of the resistor before any rewiring work...

Thanks man- JB

CajunKenny

Sorry for the delayed reply...

There isn't much around it. So, in that respect, it's fairly easy. When you say a 'standard' soldering iron, I hope you mean an iron and not a gun. Automotive type solder guns will not work for this job.

If your iron has a variable temp control, 700*f will do.

Once you're there, carefully inspect the solder joint for hairline fractures. Maximum and minimum sides. (aka: Top and Bottom ) They will typically be in a circular fashion either right around the resistor lead or in the center of the solder pad. To remove the solder, I used a solder sucker. Solder Wick will also do the job.

I agree with performing this check prior to re-wiring work. Again, the hardest part of this job is removal and re-installation of the various needles and gauge covers. They're old and delicate.

4Crawler

iTrader: (3)

The gauge sender is typically not one on the thermostat housing as I recall. Rather is is on the side of the head, between 2-3 cyl as I recall. On the t-stat housing are typical 1 or more senders for A/C cutout, A/T computer (if present) and turbo ECU.

jaredb3000

Thanks guys!

CK- no worries on the reply time- I appreciate the info! My iron is not the gun style, no temp control however... I'm definitely going to do an inspection of this before wiring work.

4Crawler- this definitely is the case, although there is a serious amount of inconsistent answers around forums and the internet at large... As it goes, having studied the wiring diagram further, the sensor in the thermostat housing is the coolant temp switch (that sends a signal to the ECU) the gauge sender is indeed further back on the side of the head. I am pretty sure its this one, that is exactly between 2-3 manifolds:



Having pulled the wire from this sensor, the needle in the temp gauge still remained at 50%; the wire itself did show an erratic resistance reading that was around 85, then it would continue up to around 120 and then cut out.

There was one thread where someone said the sender sensor is exactly in the middle of the head, of which this sensor is:



I held off on pulling this connector, as I don’t think this is it based on the connector type and size (not to mention the difficulty of getting a proper grip on it).

Although I’m going to inspect the solder in the gauge first, if I do need to rewire this, would it be possible to run a new wire without opening up the harness grouping? I’m also a little unclear as to where I would tie a new wire in, either at the juncture or at the ECU. it seems to me like the first juncture is here (the red outlines the harness, which is hard to see; the green is where I assume a juncture of wires is- unless of course the gauge wire runs directly to the ECU?):



Trying to cover all my bases so I don’t open a can of worms… Thanks yall!

corich

Jared, I can't tell if you tried this yet, but just in case, the ground for the dash is under the kick plate in the driver's footwell, just forward of the door. White with a black trace. Unscrew that, clean it up, and reinstall - that can also affect the temp gauge, from what I've read. I'd give that a crack before getting into soldering.

suncomb1

If the gauge is at 50% when not connected to the Sender it is most likely in the fail safe position (No input). I would pull the Sender and check to see if it is within spec (Factory Service Manual Procedure) If the Sender is okay, clean all of the Pipe Dope from the Sender's threads and from the installation port (Pipe Dope is an insulator). I would then use Teflon tape (a Little) on the sender's threads, install the sender and then check if the Sender's body is grounded. Next I would check for a broken wire or poor conection in the factory wiring harness / connectors; the resistance reading you get should be constant and low. If you do have a broken wire in the factory wiring harness you can run a new wire from the Sender to the Temperature Gauge directly and see if the Gauge reads and operates properly. Last, I would check the Temperature Gauge as per Factory Service Manual procedure.

jaredb3000

Greetings all,

I could sure use some aftermarket gauge advice (temporary solution) on the matter. I had to take a breather on my truck until yesterday because of school/work. Had I fixed this yesterday or today, I would have been on my way out of town, and I cant justify taking such a well taken care of ride for a 2000 trip without knowing whats going on heat-wise...

So, per the suggestions from other folks and using some deduction, all with no luck- I've most recently cleaned/checked the ground under the kick-plate, put in a new sender after cleaning everything well (the old one was looking a bit funky), ran a new wire to the gauge cluster- this was the most promising at first, as the gauge worked as it should for the first time from cold to operating temp before I reassembled the console, the unclipping/reclipping/movement however resulted in a return to erratic gauge behavior. As the problem is now narrowed down to the gauge, and not feeling comfortable soldering anything on the cluster, after maaaany hours cleaning screws, inspecting connections etc, I decided to put in an aftermarket gauge for the time being.

After expressing my concern with the length of the "universal" sending unit possibly not contacting coolant as it is much longer, dick pipe at the O'reillys assured me that the 16 1.5 adapter would work. It threads in properly, but the underside of the 16mm adapter head does not mate with the housing on the motor...

So, my questions:

1) Would teflon tape create a sufficient plugging of the fluid for a few months, or should I bag this adapter all together? I ran to op-temp w/out tape and it leaked a bit.

2) Does anyone know a part # and/or chain auto part store that might have a proper adapter for the universal aftermarket temp gauges?

3) Any input on using the aftermarket sending unit length? It seems to me it could possibly not be touching coolant-how important is this to identifying the critical moment when overheating is about to unfold?

4) Any insight as to a go-to product readily available in a chain part store much appreciated!

JB

suncomb1

Even if the overall length of the sending unit is longer it does not matter as long as the front part of the sending unit is immersed completely in the coolant. If you use Teflon tape, use as little as possible and check if the sending unit is grounded (Use an Electrical test meter) after installation. I use VDO instruments and all of their senders install properly and their gauges are accurate.