Hi - thanking everyone in advance for any help with this...

I need to know what the thermostat type should be for the 1990 Bonneville SE with the 3800 VIN "C" engine... the usual 180 degree for summer and 195 degree for winter?

It might be an issue, as the gauge never reads any higher than the 1/4 mark; I'm not sure whether it'* a linear gauge, but the lowest temp on the gauge face is 100deg and the highest is 280deg, so it'* reading, like, maybe 140-150deg)
Under normal operation I'm guessing the needle should read somewhere very near the center (straight up, at the "halfway point")

It almost acts like it doesn't HAVE a t'stat in it - and it may in fact have been removed, as this car was previously owned by an older person who only drove in the summer.

FYI, it'* probably obvious the blower doesn't get anything other than kinda-warm air out of the dash vents. I initially thought about the heater core being plugged up, except that couldn't possibly be it since the whole damn system is running cool.

Thanks!

Sounds like the thermostat is stuck open. Change it with a new one. 195* should be what you need.

Here is a guide on changing your thermostat:

https://www.gmforum.com/t277853/

THX!
Procedure was slightly different from the one posted, but the 195* did the trick...
Funny, I tested the old one and it wouldn't open up until about 205*, so the car should have gotten hotter with the old one, but it might have just as likely stuck open once it did open...
Anyway, problem solved, and thanks for your help!

Good to hear. Feel free to ask if you have any other problems. Also feel free to join in on any conversations. We enjoy just talking too.

GM gauges are notorius for not being right on. I had the following that all showed 200 as the normal operating temp. 87 Olds Regency, 91 LeSabre, 91 and 92 Park Avey'*. All 3800'*. The Park Avey'* tended to go as high as 210 with Summer heat and A/C