Oil pressure gauge barely moves (SOLVED) (1 Viewer)

Joined
Dec 9, 2007
Messages
127
Location
Marietta GA
After not getting any good feedback I tried it and posted about the results HERE. Read on for original posting.

Should I just bend my oil pressure bimetal mechanism to get it into a reasonable range?
If so where should I bend it?
Also WTF is inside the oil pressure sender?
I've been through 10 of the 50 pages returned by site search and used google to search the site to no avail.
In way of explanation:

My mechanic attached my oil pressure lead to the ground pin. Probably knocked it off while changing the fuel pump.
I drove it and noticed that it was pegged.
I moved the lead to the center and now it barely moves.
The oil pressure is good. The sender is practically new.
I checked the gauge resistance and it is 45 ohms service manual says it should be 55 ohms.
If I check it in series with a 3 watt bulb as described in the service manual it barely moves.
If I put 12.5v (starting battery) across it and moves nicely and draws 250mA which calculates out to about 50 ohms (bad ohm meter maybe?)
I'm assuming the gauge is a bimetal actuator that is heated by a resistance wire and that the "sender" modulates the current and thus the heating of the bimetal actuator.
I also assume that the resistance wire failure mode is open circuit.
Since the wire clearly heats the bimetal actuator the heating wire has full nominal function, given the previous statement.
Therefore the electrical fundamentals of the gauge are intact but perhaps the mechanical part is out of calibration.
The only way to "adjust" the mechanical part is to bend the bimetal part as far as I can tell.

I have also checked the sener per the manual.
With the engine off no continuity through the sender.
With the engine running the light goes full on for a few seconds then gets dimmer and starts to fluctuate.
If I put a current meter on it the current fluctuates after a few seconds
I can not really see a difference between high and low RPM.
WTF is going on inside the sender? I had assumed it would be some sort of variable resistor but clear from what the manual say to do for diagnostic and what I measured it isn't just a rheostat. I find the few seconds of current before it start fluctuation to be particularly perplexing.
 
Last edited:
Joined
Dec 9, 2007
Messages
127
Location
Marietta GA
Gauge is probably bad now that the wire was hooked to the ground
True it doesn't work but it would seem that I should be able to repair it. If I had to rewrap the heating wire (ie it was an open circuit) I'd be daunted but that doesn't appear to be the case.
 

tmxmotorsports

SILVER Star
Joined
Jul 3, 2016
Messages
2,114
Location
OBX Nc
Try using Google for your search if you have been using the search function on here it doesn't work all that well.
 

OSS

Joined
Jun 30, 2017
Messages
3,319
Location
Oblivion
I don't think anyone has ever made a decisive action based on what the oil pressure gauge reads. I say ignore it. Everyone else does even when it works. Older Toyota trucks didn't have an oil pressure gauge or light. Nothing.
 

tmxmotorsports

SILVER Star
Joined
Jul 3, 2016
Messages
2,114
Location
OBX Nc
I don't think anyone has ever made a decisive action based on what the oil pressure gauge reads. I say ignore it. Everyone else does even when it works. Older Toyota trucks didn't have an oil pressure gauge or light. Nothing.
Bit what about the warm fuzzy feeling it gives us to know we actually have some type of knowledge of oil pressure
 
Joined
Mar 4, 2016
Messages
1,382
Location
Boulder, Co
I don't think anyone has ever made a decisive action based on what the oil pressure gauge reads. I say ignore it. Everyone else does even when it works. Older Toyota trucks didn't have an oil pressure gauge or light. Nothing.
My buddy’s 96 Tacoma lacked one as well.
 

Spike Strip

Go Fun Me
SILVER Star
Joined
Nov 22, 2005
Messages
15,274
Location
Los Angeles
If you remove the Cluster and then the oil gauge you will most likely find a nice black burned spot in the electronics. I had a picture of one but can't find it at the moment.

Should you want to have an oil pressure gauge, now is the time to install an aftermarket one. Even an electric gauge with the proper adapters is an easy install and way more accurate than the stock gauge.
 
Joined
Oct 19, 2019
Messages
74
Location
Phoenix
Yep did that. Used site:forum.ih8mud.com/forums/60-series-wagons.27/ and didn't find anything with a variety of search terms.

That search string doesn't work (I wish it did!); the "60-series-wagons.27/" folder is not in the URL of the individual threads. (Take a look at the URL of this thread and you'll see). You could do "site:forum.ih8mud.com/threads/, but you'll get results from all the forums, not just the 60 series forum.
 
Last edited:
Joined
Feb 5, 2020
Messages
235
Location
Harpers Ferry, WV
Here’s a pic of a oil pressure gauge that’s had the connector hooked to the ground (on the left) compared to a good one (one the right). It overheats and warps the bimetallic arm contacts the plastic and melts everything.

F334E6CB-5A86-4B7D-95FE-AEB34C37C7FE.jpeg
 
Joined
Dec 9, 2007
Messages
127
Location
Marietta GA
Here’s a pic of a oil pressure gauge that’s had the connector hooked to the ground (on the left) compared to a good one (one the right). It overheats and warps the bimetallic arm contacts the plastic and melts everything.

View attachment 2630595
Both of my grounded gauges looked like the one on the right. Not burnt out. Mine was connected to ground. Not sure how long. I had flat towed it from the shop home and just parked it. Next time I used it was for a 60 mile RT at night in below freezing temps. I saw the gauge was pegged but it was to dark and cold for me to bother unplugging it so it went at least an hour like that. When I pulled it it looked like the gauge on the right except the bimetal wrapped in white wire had a distinct bend in the middle away from the direction that would raise the gauge. This is the second gauge that I have replaced because a mechanic screwed it up. The last time I pulled my old guage and tried to straighten the part but the plastic crumbled and I wasn't motivated enough to rebuild it with fiberglass and resin because everybody said it wouldn't work. Turns out that 2 out of my 2 improperly grounded gauges probably were restorable. If the wire is not an open circuit it will probably still heat the bimetal part and have some function. From your picture it isn't even clear if the gauge on the left is burnt out or just overheated and needs to be straightened out.
 
Joined
Feb 5, 2020
Messages
235
Location
Harpers Ferry, WV
Both of my grounded gauges looked like the one on the right. Not burnt out. Mine was connected to ground. Not sure how long. I had flat towed it from the shop home and just parked it. Next time I used it was for a 60 mile RT at night in below freezing temps. I saw the gauge was pegged but it was to dark and cold for me to bother unplugging it so it went at least an hour like that. When I pulled it it looked like the gauge on the right except the bimetal wrapped in white wire had a distinct bend in the middle away from the direction that would raise the gauge. This is the second gauge that I have replaced because a mechanic screwed it up. The last time I pulled my old guage and tried to straighten the part but the plastic crumbled and I wasn't motivated enough to rebuild it with fiberglass and resin because everybody said it wouldn't work. Turns out that 2 out of my 2 improperly grounded gauges probably were restorable. If the wire is not an open circuit it will probably still heat the bimetal part and have some function. From your picture it isn't even clear if the gauge on the left is burnt out or just overheated and needs to be straightened out.
Yeah probably could have been bent to fix it, but I got a multi cluster cheap off eBay and swapped that and the fuel gauge at the same time.
 

Users who are viewing this thread

Top Bottom