salinity

Thought I'd break this discussion out from another thread...

So after a water pump, t-stat, t-stat housing & rad cap replacement, I realized my temperature sensor dummy light isn't functioning (doesn't light up when I turn the ignition). I pulled the cluster to confirm it is not a bulb (it's not), I replaced the temperature sending unit (rear of the engine block) and checked the engine block to firewall ground and the indicator still doesn't light up upon turning the key. Any thoughts where to go next?

I'm considering getting an aftermarket gauge - I've read some threads on that upgrade, but haven't run across an easy "plug and play" solution (gauge that I can feed through the firewall and thread or plug into where the current temp sending unit goes). I noticed some put the aftermarket gauges in the coolant line with the coolant temperature sensor instead of on the block - what's the line of thinking here?

djb383

Coolant temp sensor needs to be in the head (not the block) or as close as possible to where coolant exits the head. Mounting a temp sending unit in the heater hose at the stat cover would be a good place. Google Trail Tech, they have digital aftermarket temp gauges. Don't think u will find a plug-n-play temp gauge.

salinity

Thanks - I believe I should have said the temp sender is on the rear of the head, not block(?). Of the 2 sensors - one at the rear of the head on the drivers side (temp sending unit) and one threaded into the thermostat housing (coolant temp sensor) - any idea which one sends a "signal" to the cluster?

djb383

I believe on a '95 XJ the sending unit at the rear of the head signals the factory dash gauge. Don't know if it also acts as the dummy light switch. The sending unit in the stat cover signals the ECU for the radiator efan. Guess it could also signal the dummy light.

Here's the digital temp gauge from Trail Tech. The sending unit would mount in the 3/4" heater host at the t-stat cover.

http://www.trailtech.net/digital-gau...rature/722-eh1

cruiser54

What happens if you ground the temp sender wire to the head with key on?

salinity

Could you explain precisely how to "ground" it? Would I simply ensure contact from the wire to the block? And would it cause the dummy light to light up upon ignition if all was well with the connection?

Thanks - I'll try this out when I get home.

salinity

Radiator elec fan - is it possible I don't have one of those?

Thanks for the digital gauge link - I'll probably look into that.

cruiser54

Yes, and yes.

salinity

A new wrinkle in the saga...

So the temp light still does not light up when I turn the ignition like other indicator lights - however, driving down the road today the temp light came on very dimly at first and then a little brighter. I drove for 1.5h (mostly highway) and it was dimly to moderatly lit the whole way, but never got nearly as bright as the other indicators. So, I'm thinking Autozone sold me a defective sedner (part #, stamp, and "look" is right), or a sender for a gauge. It's good to know the wiring likely is ok - I wish I knew if there was a coorelation between how bright it gets and when I'm in danger of overheating.

Tried 3 autoparts stores local and no one has the proper sender...

OldTires

hmm, i got the dummy lights too and mine does not come one on ignition. and i know it works because earlier this spring i had the auxilary fan out for maintenance and while driving a little stuck in traffic the light came on and then went away when i turned on the heat. haven't had any issues since the auxiliary fan went back in.

come to think about it, the only light that comes on on ignition is the oil pressure light, and then quickly goes away.

so maybe the light is not supposed to come on? though i have a 1996 model which is different than yours.

and yes, the brightness does appear to indicate the level of heat, as mine did fade away as it cooled off. sounds like yours is working correctly and you may be over heating a bit. maybe something else is going on.

cruiser54

It should NOT get brighter and dimmer as it is a simple switch. At a certain temp, the contacts close. When it cools off, the contacts open.

PocketsEmpty

you need to look into getting a full instrument cluster.

I could not drive a vehicle with dummy lights, personally.

salinity

Interesting - since we seem to have the same symptom, I wonder if you have a faulty / wrong sender as well (according to the post quoted below, the dummy light should NOT behave like this). My part # lines up with sender for light (not gauge), but still appears to be wrong.

Anyone else with a '95 XJ or similar with a dummy light out there to chime in whether a) theirs lights up upon ignition and b) if the light varies according to temperature?

salinity

Yea - as I said, I'm considering getting an aftermarket gauge - it's just not in the cards right now (limited time before heading out to sea for a while). I'd like to get the light working properly first.

salinity

I pulled the autozone part and put in a part I received from NAPA. Temp light still does not come on at ignition. I took it for a drive and I did not see the light come on at all (dimly or otherwise). Another interesting wrinkle - I tried grounding the wire to the block and the light didn't light up. HOWEVER, there must be connectivity, because the other temp sender was making the light illuminate.

Can anyone with a 95 XJ with a dummy light confirm if it does indeed come on while turning the key? Could there be a wiring difference for a gauge and a light (could I be wired for a gauge but have a light on the dash)? The connector on the wire going to the cluster is white and I know the temp sender for a gauge has a white connector (the one for a light is black). This seems odd to me, but I'm stumped...