16 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHSlow Blinking Coolant Light (turns off at temp)
Leading reported evidence
Use off-the-shelf optomax llc210d3sh microprocessor controlled infra-red sensor
Performed · outcome unconfirmed
No successful repair reported for this finding.
0
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that performed work without a confirmed outcome
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Performed · outcome unconfirmed
Yes the very early UAOS kits used an off-the-shelf Optomax LLC210D3SH Microprocessor Controlled Infra-Red Sensor from SST Sensing in the UK.
Disconnect coolant sensor, etc.) and narrow it down
No successful repair reported for this finding.
0
Reported fixes
0
Unsuccessful attempts
1
Discussions
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Discussions that contain suggestions
1
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Suggestion · Original poster
I am going to try to isolate the circuits (disconnect UAOS, disconnect coolant sensor, etc.) and narrow it down to where the failure is at least coming from.
Leading evidence: 'Use off-the-shelf optomax llc210d3sh microprocessor controlled infra-red sensor' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, the most frequently mentioned possible cause is 'issue' (1 discussions; 0 report identifying it and 1 suggest it). The most frequently discussed action is 'Disconnect coolant sensor, etc.) and narrow it down' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
Source reports, not a diagnosis or a success probability. Counts refer to discussions and can overlap.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that suspect a cause
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Suspected cause · Original poster
If your tank is original, that�s likely the issue.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that suspect a cause
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Suspected cause
My indy says it's probably the sensor for the reservoir tank I believe.
Disconnect coolant sensor, etc.) and narrow it down
Suggestion or failed attempt
No successful repair reported for this finding.
0
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that contain suggestions
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Suggestion · Original poster
I am going to try to isolate the circuits (disconnect UAOS, disconnect coolant sensor, etc.) and narrow it down to where the failure is at least coming from.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that contain suggestions
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Suggestion · Original poster
I am going to try to isolate the circuits (disconnect UAOS, disconnect coolant sensor, etc.) and narrow it down to where the failure is at least coming from.
These are separate views of the same evidence. Frequency alone does not establish a fix, and these counts must not be added together.
Disconnect coolant sensor, etc.) and narrow it down
No successful repair reported for this finding.
0
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
Discussions that contain suggestions
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Suggestion · Original poster
I am going to try to isolate the circuits (disconnect UAOS, disconnect coolant sensor, etc.) and narrow it down to where the failure is at least coming from.
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Suggestion · Original poster
I am going to try to isolate the circuits (disconnect UAOS, disconnect coolant sensor, etc.) and narrow it down to where the failure is at least coming from.
Counts describe captured discussions, not unique people or a diagnosis. Author identities are not reliably stored. Exact duplicate evidence is counted once across matching discussions; one discussion counts at most once per action/state. Multiple repairs reported together remain a combination. Suggestions and failed attempts do not establish a fix. Matches cover whole discussions and can include related faults, model variants and incomplete threads.
16 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
Rennlist: 1 discussions
0 evidence records excluded for query context · 0 excluded by outcome qualification · 0 adjusted by outcome qualification.
0 acknowledgements have no verified action link; they do not establish a repair result.
Generation: 20261027T020439Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
1999 C2.
So, I�ve read up on this and this is an intermittent problem so far. I see there are 2 basic conditions for the light: low coolant level, and bad engine compartment fan.
I have a full coolant tank at max, which I topped off. I have no leaks, no drips, no evidence of a drying leak that I can see. I have replaced the expansion tank a few years ago and it�s been maybe 4k miles.
I have a UAOS, but I am not sure it�s related since it has a track drain.
The slow blink starts at cold start and if I restart the engine at warm, so near 180 mark, the light doesn�t come back. My coolant temps are pretty normal - needle straight up while driving around and maybe in the middle of �zero� during stop and go. Drops back down with speed.
I had a track day a few weeks ago and the car�s temps were rock solid. It gave me a lot of confidence that cooling and oiling were fine.
Is this a failing level sensor? Has anyone experienced this?
I had similar behavior with a failed (stuck open) thermostat. On cool days (below 50*) coolant temps would drop to a certain point where the light would flash.Would go away if I drove the car hard enough to keep the temperature in range.
Very interesting. I replaced with LN�s low temp thermostat about 4k miles ago as well, and I think the engine comes up to temp in a reasonable time - like 5 miles or so.
The uaos sensor can cause a false blink but im pretty sure that issue has ben rectified. U may want to pm
@Porschetech3
? There r a couple reasons for the slow blink so search how that fault is activated.
After I started looking up the UOAS coolant light conditions, I found very similar symptoms here:
https://rennlist.com/forums/996-foru...m_content=post
I am going to try to isolate the circuits (disconnect UAOS, disconnect coolant sensor, etc.) and narrow it down to where the failure is at least coming from.
Yes the very early UAOS kits used an off-the-shelf Optomax LLC210D3SH Microprocessor Controlled Infra-Red Sensor from SST Sensing in the UK. This one was too sensitive to water vapor/steam and could cause a false warning...
I worked with the Engineers at SST SEnsing to develop an upgraded Sensor ( LLC210D3H-442) that is specifically designed to work with UAOS and is not sensitive to water/vapor/steam...
So could be an early Sensor or one of the other two sensors, the low coolant sensor or the engine compartment temp sensor,. Any of the three can cause the "Slow Flash" ...
Thank you for the info. Tonight I am going to disconnect some wires and see if I can isolate the sensor it�s coming from - that is, if I can reliably reproduce it.
Well, I have a similar issue and do not currently have the UAOS (yet!). When cold, if I take a corner a bit sharp, the slow blinking light comes on but once up to temp, if I turn the car off and back on it goes away and stays away. My indy says it's probably the sensor for the reservoir tank I believe. I have no leaks and it's an easy fix at a stoplight so I haven't tracked it down.....
I read about a TSB for early cars and their expansion tanks with this condition - the coolant sloshes around and triggers the light. If your tank is original, that�s likely the issue. Sounds like it may be since a hard corner triggers it.
I am thinking this was a loose connection in the harness. I simply moved the harness around and it hasn�t come back.
That being said - is the light off because the connection is completely severed? Or is this working the right way now? Time will tell � I�ll keep investigating.
The wiring would have to be "grounded" for the slow blink to come on .... That's what the Low Coolant and UAOS Sensor does, it "grounds " the circuit thereby activating the Warning .... Outherwise the circuit is "floating " untill grounded ...
Yes ..You need the Custom made Sensor by SST Sensing that was tuned especially for us... LLC210D3SH-442 ...
Your engine ( and climate conditions ) produces more water vapor than normal and the very Sensitive Standard LLC210D3SH is being activated by it at times...
This is a source reference. Confirm exact model applicability in the original material.
