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Discussion Starter #1
Folks,

The 91 164L temperature gauge red warning light comes on and off intermittently from immediate cold startup throughout any trip.
The temperature gauge appears to be fine and reading as expected.

Past experience has taught me to attend initially to the contacts and I thoroughly cleaned the two terminals at the thermostat housing.
I read the few earlier posts but before I start pulling things apart to follow the wiring I figured I might find out some late breaking news on the forum.

Any ideas?

Ta,

Neville.
 

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I would suspect at this point a bad sensor, that is if you are sure the wiring is intact and clean. Mine did this for a bit after I bumped the contact one day. After a while it went away, so in my case it was the contact. Keep an eye on it for a bit, then order a new sender if all else checks out alright.
 

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I have exactly the same symptom. I'm leaning towards a sensing-bulb replacement as well. Though, why the connection inside the bulb would go intermittent is beyond me - you'd think it would be sprung firmly 'closed'. Perhaps the low current allows oxidation to occur.

One idea I had was to 'cook' the switch a few times in an oven set to 120 degrees C, the hope being that once the switch was cycled on/off, it would become more reliable.

-Alex
 

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When somebody finds a sure way to fix the problem let me know. It seems it is very hard to buy a good new working aftermarket sender. I lucked out and had one NOS OEM sender in my stash that fixed my 91B, but daughter's 91B has had light problem for a long time. I haven't found a good used one in my parts stash yet to fix it.
 

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Discussion Starter #5
Folks,

The temperature gauge warning light has been on for about four months.
Now the temperature gauge has stopped working.

CARDISC does not point blame at the gauge itself nor the sender unit, rather the inter leading wires and points.
I have re-checked the points at the sender.

Before I go out in the cold (even here in NE FL) and check the dash connections at the gauge I figured to bounce this off the Learned Forum.....

It "feels" to me like the sender unit on top of the thermostat has ceased to send.
Do these units commonly fail?

Does anyone know where these senders can be purchased, or whether in fact they can be repaired?
I can repair almost anything if it is repairable.....

Any input will be greatly appreciated as always.
 

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Make sure you have a ground wire bolted to the center thermostat casting that the switches are threaded into. There is a provision for this between the two senders.
Charles
 

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Same problem here. She'll read just a hair over 175 and the light will blink on and off in traffic. Used to get to the third hash mark in summer driving with no light. I'm losing a ton of coolant, but it sure doesn't seem to be getting in the exhaust. Can't wait for it to get warm enough to start figuring out what it actually is.
 

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When I was losing coolant it was from a pinhole leak in the bottom hose. It only leaked when car was running so there was no telltale puddle. I saw it during inspection when car was being smog checked.
 

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When I was losing coolant it was from a pinhole leak in the bottom hose. It only leaked when car was running so there was no telltale puddle. I saw it during inspection when car was being smog checked.
That's exactly what I think/hope it is.
 

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... I'm losing a ton of coolant, but it sure doesn't seem to be getting in the exhaust. Can't wait for it to get warm enough to start figuring out what it actually is.
You might want to check your engine oil! If the oil is cloudy or oil level is high, then you likely have a headgasket problem! Also check OLIO cap to see whether there's excessive "mayonnaise" stuff! If you don't find these and things look OK, then at least you can rule out coolant getting into the oil!

Here's a way to determine whether the temperature warning light sensor is bad. The warning light sensor for 12V cars ('91-'93) is "normally closed" (24V sensor is different and it looks like they are either "normally open" or of high resistance ~10M ohms). It means if the temperature is less than 239F (according to manual), the sensor "switch" is closed and it provides a ground path to the orange-black wire. To test, you can connect a jumper wire from a good ground directly to the orange-black wire. If the warning light does not come on any more, then the problem is at the sensor - most likely due to too much resistance from that terminal to ground. If the light still comes on, then the problem is at the wiring or the AR control unit side. The wire goes through the big round connector G151 behind the firewall (close to the HVAC blower), you can try to clean that connector (pin 16 in particular) in case it is a poor connection there.
 

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You might want to check your engine oil! If the oil is cloudy or oil level is high, then you likely have a headgasket problem! Also check OLIO cap to see whether there's excessive "mayonnaise" stuff! If you don't find these and things look OK, then at least you can rule out coolant getting into the oil!

Here's a way to determine whether the temperature warning light sensor is bad. The warning light sensor for 12V cars ('91-'93) is "normally closed" (24V sensor is different and it looks like they are either "normally open" or of high resistance ~10M ohms). It means if the temperature is less than 239F (according to manual), the sensor "switch" is closed and it provides a ground path to the orange-black wire. To test, you can connect a jumper wire from a good ground directly to the orange-black wire. If the warning light does not come on any more, then the problem is at the sensor - most likely due to too much resistance from that terminal to ground. If the light still comes on, then the problem is at the wiring or the AR control unit side. The wire goes through the big round connector G151 behind the firewall (close to the HVAC blower), you can try to clean that connector (pin 16 in particular) in case it is a poor connection there.
I've been keeping close tabs on the condition of both the oil and the coolant since I've had this issue, and to date, both are perfectly clear, with no buildup on dipstick, oil cap, coolant cap.

You're confirming what I expected about that temp sensor, I just need the warm(er) days to check it out. I'll be testing that theory, as well as looking for the leak as warm days get here. Thanks.
 

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Testing temp gauge in a 164

Not to test the red light BUT to test the gauge itself you can pull larger of the two terminals off temp sender on mid thermostat housing and ground end of wire to engine and turn on key if needle goes full hot then gauge and wiring good.

This won't work to test red over temp light though on 12v models not sure about 24v red light as sender and circuit wiring different.
 

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Discussion Starter #13
Bob and Steve,

Using your combined directions I have determined the fault is likely at the sensor itself.

IE: When grounding in turn the two wires the gauge works and the red light goes out.

If I take off the sensor is there any way to try and fix it?

I don't see a new sender available anywhere......

Ta,

Neville.
 

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Neville,

I doubt one can easily take apart the sensor and fix inside. Try measure the resistance of the temperature warning light terminal to ground. One of mine is ~8 ohms and that turns off the warning light. At some higher resistance (or open circuit), the warning light will come on! If your sensor's resistance is not too high, you might get away by adding a resistor in parallel to reduce the resistance to "try" to make it works. But you really have to play around and test it out to see whether the warning light also comes on when it should. Now, the question is how important is this light to you. If it is important, I think replacing the sensor with a good one is the way to go. But, if it is not that important (and you know your car well ;)) you can disable the red light by grounding the signal wire!

The temperature gauge sensor terminal resistance start off at about a few K ohms when cold and it goes down to a few hundred ohms (?) when hot.
 

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Both Difatta ans Alfa parts lists they have the sensor 60540639 which is correct part number for 12v 164 models but red light side may not work. However the gauge side of sender will work OK.

Now I don't know if one Alfa parts at twice the price of difatta is OEM or after market one but difatta one is after market and red light side not made correctly on the ones I got from them.

That being said if you want gauge to work get one of them.

You can see if Alfa parts catalog in CA has correct one.
 

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Discussion Starter #16
Steve,

Alfa Parts does not list that part number (6054063900) or any coolant temp sender unit that I can see.....Alfa Parts Catalog - Alfa Romeo parts online store

Do you think APEDIRECT is worth a call for a used unit?

I hate disabling red lights etc as it detracts from the originality of the design.

Also I want Teen to notice red lights and not think they are to be ignored.

Neville.
 

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AR 164 temp gauge sender 60540639

Yes they do list it.

You can search our inventory by part name, Alfa year and model or Alfa Romeo part number.

Search For The Following Word(s): 60540639



Code Name Price
60540639 WATER TEMPERATURE GAUGE SENSOR 164 BLACK CAP


There are no zeros on end of part number. Now is it OEM NOS or aftermarket?
 

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Discussion Starter #18
Steve,

Indeed as always you are right.

I found the item in Alfa Parts and a request is in to establish whether it is OEM or what.
I requested a picture as well but have little faith in seeing that.
If the email elicits no response I will call them during the week.

$65 plus shipping etc is quite expensive......

Neville.
 

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Steve,

Indeed as always you are right.

I found the item in Alfa Parts and a request is in to establish whether it is OEM or what.
I requested a picture as well but have little faith in seeing that.
If the email elicits no response I will call them during the week.

$65 plus shipping etc is quite expensive......

Neville.
You may not get a picture but I am pretty sure you will get a reply from Jon or Ruth Ann.

Difatta's aftermarket one listed under same Alfa part number on their web site is about half the price but red light wired for 24v models I think as I could not make red light stay out using one of them on my 12v. But as I said gauge side works fine.
 

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Discussion Starter #20
Yep I definitely need that temp gauge working fine.

Today the Teen drove me in endless circles around the city center practicing for the big test on Tuesday.
I worried needlessly at times whether the temperature was going up and we would not know until too late.
I am getting old....the Alfa cooling system is working just fine since I reverted all the bogus hot wiring to original spec.
 
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